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jugs
01-02-2011, 01:12 PM
Not wishing to hijack an other thread.


Other than for decoration what’s with this obsession with scraping/ flaking/fish-scaling.

In days of old when machine beds were planed – (leaving long score marks) & shafts/bearings were turned/bored with single point tools –( giving a microscopic ploughed field finish) with accuracy’s of a few thou & dubious lubrication, it was necessary to smooth off the high spots by scraping.

Now we have modern machining methods that can give surfaces measured in microns instead of thous, you have a perfectly machined / ground /honed surface, why on earth would you want to destroy the bearing surface & the accuracy by scraping ???

I’ve heard it said (by people that should know better) that "it improves lubrication, as the oil sits’ in the hollows".
In fact what happens is as a load is applied, the crests can break through the oil film & rub against the opposite surface causing wear. The hollows do provide a handy place for small grit particles to mix with the oil to give an effective grinding paste.:eek:


Lubrication is always best served by large areas of smooth (fed by a few well placed big oil feeds) faces, so the oil film is NOT broken by crests & hollows.

john
:)

DFMiller
01-02-2011, 01:32 PM
John,
One thing it has going for the average HSM is you can fix what you might have or get without having a large surface grinder.
Your new or old with that slightly misaligned or worn bed can be tweaked with some enthusiasm and a few hours of your timed.
When I got my mill table ground a few years a go the shop said if I truly wanted it right they would scrape it in for me. This would tell me that they feel that scraping has its place.
Dave

John Stevenson
01-02-2011, 01:45 PM
Thats why they invented half round scrapers so they can scrape to microns the millions of ball races that are made DAILY.

You know the ones we take for granted to run millions of revolutions with scanty lubrication.

hareng
01-02-2011, 02:14 PM
If its ground right it wont need scraping, fact.
Lost the knack of scraping now but have done it upon request after a proper grind.

Wish i had a tenner for every time i seen a scraping job where the owner said ive only took a couple of thou off, many a time 12 thou to put right.
Theres grinders and theres grinders dont expect a lot for cheap prices.

Another way of looking at it is more surface/contact area spreading the load. Scrape even if its for oil pockets it reduces substantially the contact/wear area - subsequently machine slides wont last no where near as long.
Find me one decent lathe thats had the beds and slides scraped from new. If you want shear quality take a look at Smart and Brown or DSG, no scraping there.

J Tiers
01-02-2011, 02:51 PM
Other than for decoration what’s with this obsession with scraping/ flaking/fish-scaling.

In days of old when machine beds were planed – (leaving long score marks) & shafts/bearings were turned/bored with single point tools –( giving a microscopic ploughed field finish) with accuracy’s of a few thou & dubious lubrication, it was necessary to smooth off the high spots by scraping.

Now we have modern machining methods that can give surfaces measured in microns instead of thous, you have a perfectly machined / ground /honed surface, why on earth would you want to destroy the bearing surface & the accuracy by scraping ???


Wow, did YOU ever miss the point..........

If its ground, let it be, assuming it was ground right. Ground badly, it's as bad as a hack scraping job.


scraping/ flaking/fish-scaling.

three, or at least two, different things which you have lumped together....

"flaking": A method of digging "pits" in a good surface, hopefully in a "decorative" pattern. Alleged to provide oil pockets, probably largely a lot of hooey, as a good scraped surface OR ground surface, does fine. Some folks want it, so makers would provide it.
Often done crudely, perhaps with an angle grinder, when a machine is put up for sale by bumpkins on ebay. Secondary references under "ebay" , "blue porch paint", "hack job", "Bubba" etc.

"Fish scaling": something done at the lake, usually..... otherwise similar to flaking, in a particular pattern. Ebay references apply.

"Scraping": a way using hand methods without a $100,000 machine, to make a flat surface good to tenths, with specific desired relationships to other surfaces, i.e. parallel to them, at right angles, or any other angle/distance desired to provide the proper functionality of the machine. Requires skill and mildly expensive equipment to avoid a "hack jpb"

"frosting": when not applied to cakes, a decorative scraped finish providing that "pride of ownership" response in a machine buyer. Otherwise identical to scraping, since it is scraping with a particular technique to give a pattern. Can also be applied afterwards, does NOT involve digging pits in the surface.

"grinding" : when done right, a method of finishing machine slides to similarly accurate tolerances as scraping, but with "automated" methods, faster, and potentially better. Requires expensive machinery and skill to avoid a "hack job". The expensive machine may have been "scraped-in" for accuracy........

.RC.
01-02-2011, 03:00 PM
[quote=Jonny
Find me one decent lathe thats had the beds and slides scraped from new. If you want shear quality take a look at Smart and Brown or DSG, no scraping there.[/quote]

They are scraped.....Look under the carriage or tailstock..

form_change
01-02-2011, 03:08 PM
I was once told a story about a car manufacturer that had product failures because a journal surface was too smooth and so did not keep the oil in place, so I'm not sure that the concept of smoother is better is necessarily correct. Tribology is not that simple.
Scraping can be replaced in some cases by grinding, but grinding machines are not cheap so for irregular use on large parts they are hard to justify. Having just looked at a lathe bed re-grind, the choice of provider was limited and expensive. Getting a flat reference surface from a grinder also requires that the grinder is unworn - not necessarily the case.
While some scraping is done for decorative effect (there is scraping on my mill that a carriage can never come in contact with), it is a legitimate method for getting mating parts well bedded in. The trade off is time. Scraping is far cheaper (cost of tools, materials) and is a lot more flexible but takes time, where as grinding requires a larger capital investment, is more limited in what it can easily do (eg removing metal up to a corner) but has far greater metal removal rates.

Michael

bborr01
01-02-2011, 03:24 PM
Can you imagine trying to use a surface grinder that had ways that were as smooth as a gage block?

Brian

dp
01-02-2011, 03:27 PM
Nick Müeller has some great videos on YouTube that show how scraping can quickly and accurately restore or improve mating machine surfaces.

Here's a starter: http://www.youtube.com/watch?v=esAqz6bCVyQ

After watching, the why of scraping may become more clear.

MuellerNick
01-02-2011, 03:28 PM
Thats why they invented half round scrapers so they can scrape to microns the millions of ball races that are made DAILY.


Ahhh ... wrong! :)
Bearings are first ground and then the nice fine finish is ruined by honing them to give small defined pockets.
They do NOT want small groves along the rolling motion, the want small "scratches" diagonal to them. Look in a car's cylinder.


Nick

Tony Pratt
01-02-2011, 03:44 PM
[QUOTE=dp]Nick Müeller has some great videos on YouTube that show how scraping can quickly and accurately restore or improve mating machine surfaces.

Here's a starter: http://www.youtube.com/watch?v=esAqz6bCVyQ

His work looks and is impressive, but that sort of skill doesn't come overnight and quite a challenge for any amateur. Then again if a surface grinder is not avaliable it is always an option.
Tony

dp
01-02-2011, 03:46 PM
His work looks and is impressive, but that sort of skill doesn't come overnight and quite a challenge for any amateur. Then again if a surface grinder is not avaliable it is always an option.
Tony

I took one of Forrest's scraping classes and I wouldn't hesitate to take on a project like that. In fact I have :)

The worst part of it is the back ache.

Tony Pratt
01-02-2011, 03:54 PM
Fair play to you, I can't argue with that!
Tony

Black Forest
01-02-2011, 04:04 PM
If Nick can do it anybody can!

John Stevenson
01-02-2011, 04:21 PM
Can you imagine trying to use a surface grinder that had ways that were as smooth as a gage block?

Brian

Yes.
Last time I was in China they were installing one of the latest Swiss slideway grinders for doing the beds on the CNC's.

It was on linear rails with a rack cut into the rail and the drive was by servo motor

tdmidget
01-02-2011, 04:43 PM
Ahhh ... wrong! :)
Bearings are first ground and then the nice fine finish is ruined by honing them to give small defined pockets.
They do NOT want small groves along the rolling motion, the want small "scratches" diagonal to them. Look in a car's cylinder.


Nick

When I worked in a bearing factory I ground them to .0001 sphericity and single digit finishes.

.RC.
01-02-2011, 04:45 PM
Yes.
Last time I was in China they were installing one of the latest Swiss slideway grinders for doing the beds on the CNC's.

It was on linear rails with a rack cut into the rail and the drive was by servo motor

Well there you go, obviously this style is utter rubbish due to the banana shaped ways that come standard with chinese machines :D:D

Mcgyver
01-02-2011, 04:53 PM
Not wishing to hijack an other thread.


Other than for decoration what’s with this obsession with scraping/ flaking/fish-scaling.

In days of old when machine beds were planed – (leaving long score marks) & shafts/bearings were turned/bored with single point tools –( giving a microscopic ploughed field finish) with accuracy’s of a few thou & dubious lubrication, it was necessary to smooth off the high spots by scraping.


John you've mistakenly come to the view that scraping is for a finish or oil retention; not the case. Scraping is for accuracy, often better than grinding and commonly on parts that would be nearly impossible to grind on the equipment at hand. In essence its just a way to localize where material is removed. Because of the extremely small DOC, after several iterations the variance becomes say +- a tenth to the accuracy of the reference (ie granite surface plate). If the work is say a 1" x 1" x 10" long bar it would take a man who knew what he was doing a fair bit of fidgeting to get it as flat as is routine for scraping (I'll sometimes rough scrape a side then grind the rest when it matters)

In a shop without a grinder, it lets you make all manner of plates, parallels, squares angle plates etc as accurate or more so that you can do by grinding. In a shop with a grinder, it lets you do odd shaped parts, parts too large for the grinder....try to set up a 20" long carriage for grinding the dovetails.....I have a surface grinder but end up scraping frequently. Finally, it provides a technique whereby machine tools can be brought back to better than original condition - something that's attractive to those of us wanting champagne quality machines on a beer budget.

I see it like filing imo, a basic shop skill with lots of applications. There's guys out there who think they don't need to know how to file....but I bet the guys who's work you admire do. I can see why some commercial guys wouldn't see the value ......but it makes sense for them to buy whatever high end tooling they need, have access to big high quality surface grinders and aren't interested in rebuilding machine tools.

John Stevenson
01-02-2011, 04:57 PM
Well there you go, obviously this style is utter rubbish due to the banana shaped ways that come standard with chinese machines :D:D

I wasn't talking about the hobby machines but the commercial ones.

http://www.allbusiness.com/personal-finance/investing/736157-1.html

;)

lazlo
01-02-2011, 06:55 PM
John you've mistakenly come to the view that scraping is for a finish or oil retention; not the case. Scraping is for accuracy, often better than grinding and commonly on parts that would be nearly impossible to grind on the equipment at hand.

I agree with the overall sentiment, but I think modern grinding machines, like John is describing, have surpassed the accuracy that scraping can achieve over long distances (the length of a machine bed). I don't think there's been a machine made since the 1930's with a scraped bed. The saddles are scrapped to fit, of course.


In a shop without a grinder, it lets you make all manner of plates, parallels, squares angle plates etc as accurate or more so that you can do by grinding.

Agree 100%! Although now I have a good surface grinder, I find I'm doing a whole lot less scraping. I ground that Eclipse toolmaker's block you sent me, and it came out really nice, aside from that drill divot :)

.RC.
01-02-2011, 06:59 PM
Of course you can not scrape hardened steel or cast iron easily...

Nearly every machine way for a long time has been hardened..

lazlo
01-02-2011, 07:03 PM
Of course you can not scrape hardened steel or cast iron easily...
Nearly every machine way for a long time has been hardened..

True, but you could scrape it then hard chrome it, like Bridgeport et al did.

My point being that modern ultra-precision machine tools "get by" just fine with a ground bed.

By the way, Alexander Slocumb's excellent book "Precision Machine Design" has a chapter on the design of a theoretical T-based ultra-precision lathe, with many references and analysis of Livermore's LODTM -- at the time, the world's most accurate lathe (maybe it's still is?). LODTM uses ground hydrostatic bearings.

"Specialized hand-finishing processes" is clearly hand scraping -- option 1 of Slocumb's design:

http://i164.photobucket.com/albums/u15/rtgeorge_album/Slocumb.png

gnm109
01-02-2011, 07:15 PM
Jugs' original post here "Scraping! Why" mentioned scraping in the title but is really about flaking and scaling.

Even I, with my Chinese Lathe that proudly states on its placard that it has "Induction-Hardened Bed Ways", know the difference.

From what I've been able to glean, scraping is a repair technique used to repair worn bedways.

Flaking and fish scaling are, on the other hand, processes used to retain oil on the beds and sliding parts on lathes and mills. It's odd-looking to me and sort of annoying if it's overdone, as is often the cae.

I assume that you all may have seen the scraping work that Beckley (Harry) has done on several threads on that other website. It's on the Monarch section. Now that's scraping.

My Enco has no flaking on it anywhere, by the way.

lazlo
01-02-2011, 07:19 PM
Jugs' original post here "Scraping! Why" mentioned scraping in the title but is really about flaking and scaling.

Oh geez! Nevermind :o

J Tiers
01-02-2011, 07:35 PM
Jugs' original post here "Scraping! Why" mentioned scraping in the title but is really about flaking and scaling.

Even I, with my Chinese Lathe that proudly states on its placard that it has "Induction-Hardened Bed Ways", know the difference.

From what I've been able to glean, scraping is a repair technique used to repair worn bedways.

Flaking and fish scaling are, on the other hand, processes used to retain oil on the beds and sliding parts on lathes and mills. It's odd-looking to me and sort of annoying if it's overdone, as is often the cae.



Ah, but he SAYS :
scraping/ flaking/fish-scaling

I pointed out the differences above....

Here's another case, fresh from the shop.....

Surface ground parallel, blued as test. contact at ends only , with typical surface grinder regular "peaks".
http://img.photobucket.com/albums/0803/jstanley/paral1.jpg

After a round or two of actual, real scraping.... not perfect, but better.
http://img.photobucket.com/albums/0803/jstanley/paral2.jpg

This one is probably hardened, I scraped with carbide scraper and it didn't dig in without effort. I need to make it match the other one of the pair, for scraping (actually measuring during scraping) purposes. I'll check it with a tenths reading indicator on the granite flat.

With a ground finish that is flat, the "marking" probably would be a "smear", without the "spots" typical of scraping.

dp
01-02-2011, 07:48 PM
Here's another case, fresh from the shop.....

Hmmm - I've gotten grinds that good with my radial arm saw used as a grinder.

Mcruff
01-02-2011, 07:49 PM
Ah, but he SAYS :

I pointed out the differences above....

Here's another case, fresh from the shop.....

Surface ground parallel, blued as test. contact at ends only , with typical surface grinder regular "peaks".
http://img.photobucket.com/albums/0803/jstanley/paral1.jpg

After a round or two of actual, real scraping.... not perfect, but better.
http://img.photobucket.com/albums/0803/jstanley/paral2.jpg

This one is probably hardened, I scraped with carbide scraper and it didn't dig in without effort. I need to make it match the other one of the pair, for scraping (actually measuring during scraping) purposes. I'll check it with a tenths reading indicator on the granite flat.

With a ground finish that is flat, the "marking" probably would be a "smear", without the "spots" typical of scraping.

Very poor example, that thing was ground by a butcher with a rock from his garden, I have run a surface grinder 1000's of hours, all of ours molds were blued on the ground surfaces and none of them looked even remotely like that! If the machine is belt driven on the hand cranks with no rack gear you won't get that scallop you show either, that can also be from an out of balance wheel or one not dressed properly. Oh and the contact on the ends was from wheel choice, to heavy of a cut or feed rate, like I said, pi$$ poor guy on the grinder, in fact who ever ground it was a butcher, inexperienced or it was done in production to a tolerance point (read cheap).

J Tiers
01-02-2011, 07:58 PM
Sure, sure...... no doubt you are correct.;)

But "poor example"? I think NOT.......... better you say "TYPICAL example of "production" grinding to a tolerance."

This is an example of commercial made-in-USA surface grinding, and not recently, either. These were ground back a while in the days of "not quite THAT cheap" production.

Goes to show that inexperienced grinder hands are not necessarily ANY better than inexperienced scraping hands..... Which directly approaches the original point, as to why scrape if you can get at a surface grinder.....

To which the answer is, a good grinder needs a good operator, or the results won't be good.

Mind, the difference between ends and middle was only TENTHS, and not many of them, as-ground.

But, the bearings in a grinder are only so stiff, so round, etc. the frame is only so stiff, with only "that" much damping, etc..... all these factors lead to issues with grinding. And, ALL grinding is to "tolerances", it just makes a difference how WIDE they are.... And, often you don't get a choice, or if you DIY grind it, maybe you don't do so well, because your grinder has 0.001 sag as the table travels....... or the production shop's does, just as you please.

Scraping requires only a flat as the basic reference, everything else is generated from that. In fact, a flat can be generated to any degree of perfection desired with NO extra measuring tools...... you just need to make 3 at a time.

lazlo
01-02-2011, 08:20 PM
Very poor example, that thing was ground by a butcher with a rock from his garden, I have run a surface grinder 1000's of hours, all of ours molds were blued on the ground surfaces and none of them looked even remotely like that!

I'm a complete newbie to grinding, and those hardened S7 power hammer dies I ground blued-out really nicely. But like Mcruff says, I've got a *ton* to learn...

I tried to surface-grind the curve out of a warped gib on my Eisele cold saw, and I was not successful (although it was a lot better than when I started). Yes, I've read the grinding guides on shimming the warp, but I simply could not a long, thin strip to stop moving when you turn the magnet on.

MuellerNick
01-02-2011, 10:00 PM
It's simply not true that scraping is no longer used on new machines.
High precision machines are still scraped. From Swiss, Japan, Germany. Hauser, Kitamura, Spinner. Just to name a few.

My MAHO (built '82) has ground and scraped (flaked) ways all over. That's not decorative, it's functional. You can't see most of them without removing the covers.


Nick

Arthur.Marks
01-02-2011, 11:42 PM
It's simply not true that scraping is no longer used on new machines.

I would agree here; however, I tend to see one of two mating surfaces ground and the other scraped more than both. There are surely plus and minuses to each, but one mated to the other has much to its benefit, IMO. I will note that I bought a $4k+ tailstock for a Schaublin lathe a little more than a year ago. They still scrape their mounting bases on the tailstocks. The lathe beds, though, are entirely ground. The more I read on both processes, it seems that it is two methods to the same end. Both, of course, can be done with great skill and precision... or not.

MuellerNick
01-02-2011, 11:55 PM
It is true, that in modern (or not antique) machines, only one parter is scraped.


Nick

Allan Waterfall
01-03-2011, 05:42 AM
Ahhh ... wrong! :)
Bearings are first ground and then the nice fine finish is ruined by honing them to give small defined pockets.
They do NOT want small groves along the rolling motion, the want small "scratches" diagonal to them. Look in a car's cylinder.


Nick
When I worked as a bearing inspector at RHP precision bearings the inner and outer tracks were ground only,any scratches meant a reject bearing.

Allan

Ian B
01-03-2011, 06:36 AM
On the hand scraping of the undersides of lathe saddles & tailstocks, isn't this done to remove metal in the centre such that the saddle / tailstock only contact the bed on 4 pads at the corners? If not done, the ends may wear more than the middle and allow the components to rock slightly.

Ian

J Tiers
01-03-2011, 08:35 AM
When I worked as a bearing inspector at RHP precision bearings the inner and outer tracks were ground only,any scratches meant a reject bearing.

Allan

I don't think Nick meant "scratches", but a pattern of machining marks that is not anything like "mirror polished". While you see marks, the surface is actually very smooth.

Scraping is like that... you see all these "gouges" in the surface, put in by a coarse, brutal, uncalibrated, hand process, with a very visible pattern of cris-crossing marks.

Then you run your hand over the surface, and it is about the smoothest surface you have ever felt.

Still not as good as a bearing though.

John Stevenson
01-03-2011, 08:43 AM
Scraping was done to correct errors caused by the machining of the day.

Anything after that is a throw back.

lazlo
01-03-2011, 10:54 AM
It's simply not true that scraping is no longer used on new machines.

I knew that was going to cause angst with the scraping aficionados, but it's true. :)


High precision machines are still scraped. From Swiss, Japan, Germany. Hauser, Kitamura, Spinner. Just to name a few.

Like I said Nick, the beds are ground, the saddles are scraped to fit.
Deckels have always been ground, with scraped saddles. According to MAHO's web page, their bed are ground.

Yes, there are small companies like Kitamura, Dixie, and SIP that scrape sections of their machines, but that's marketing shtick, in my opinion.

Hell, SIP and Dixie grind the bed and guideways, and then proudly shows scraping the precision ground top of a linear bearing block. I mean, come on! :)

http://www.moriseiki.com/dixi/english/company/img/scraping_p_slider.jpg
http://www.moriseiki.com/dixi/english/company/img/scraping_p_slider_type02.jpg

dp
01-03-2011, 11:07 AM
Yes, there are small companies like Kitamura, Dixie, and SIP that scrape sections of their machines, but that's marketing shtick, in my opinion.

I almost quoted before your edit!

http://www.kitamura-machinery.com/hand-scraping/

That looks like a serious commitment to precision and not so much shtick.

Edit: In my opinion. :D

huntinguy
01-03-2011, 11:14 AM
Roller pack ways are not the same as traditional ways. The current Moore I run is roller pack and I see no signs of scraping in the bed ways. Column is scraped in.

The older Moore... Well I watched with amazement as the Moore tech scraped in the machine.

Most of the modern CNC machines... roller pack or other are compensated by computer, so any small error is removed... at least where the testing is done.

As to grinder ways and smoothness... Unless I am mistaken, most grinders, save for bearing pack types, run on a film of oil. At least the ones I have taken a close look at. Not sure if it really matters how smooth the ways are as long as the oil film stays uniform and the feed pressure of the oil is constant.

lazlo
01-03-2011, 11:39 AM
http://www.kitamura-machinery.com/hand-scraping/

That looks like a serious commitment to precision and not so much shtick.

Look at this picture on that Kitamura page. They have ground guide ways, which is consistent with my previous statement:


"I think modern grinding machines, like John is describing, have surpassed the accuracy that scraping can achieve over long distances (the length of a machine bed). I don't think there's been a machine made since the 1930's with a scraped bed. The saddles are scrapped to fit, of course."

http://www.kitamura-machinery.com/Images/manufacturing-6.jpghttp://www.kitamura-machinery.com/Images/manufacturing-5.jpg

So here's something to consider: only the small boutique manufacturers like Kitamura, SIP and Dixi brag that they still handscrape sections of their machines. So are the machines from these small manufacturers better, or more accurate, than the large volume machines like MoriSeki (who owns Dixi)?

If the oddity of that Dixi tech scraping the top of that linear bearing block is not glaringly obvious: they're building a machine that runs on hardened and ground roller ways, that are mounted on ground bed references, but the Swiss value-add is that they scrape the hardened and ground top of the linear bearing block. :confused:

This reminds me of the Gerstner video that was posted recently on PracticalMachinist where they proudly proclaimed that each drawer was hand finished. They actually had a guy who's full-time job was to sit down with a file and sandpaper and make sure each drawer, of every Gerstner box made, slid smoothly.

There were howls of protest that if they used modern woodworking machinery, that wouldn't be necessary, but it sure was quaint :)

jugs
01-03-2011, 12:19 PM
As to grinder ways and smoothness... Unless I am mistaken, most grinders, save for bearing pack types, run on a film of oil. At least the ones I have taken a close look at. Not sure if it really matters how smooth the ways are as long as the oil film stays uniform and the feed pressure of the oil is constant.

All machines run on a run on a film of oil somewhere.

The thiner the oil film the the more accurately the "floating part" follows the fixed part in 2 dimensions, but excessive / shock loads can overcome the static pressure between the surfaces if the oil film is punctured by peaks in the surface or by dirt/grit.

A thick oil film prevents contact BUT allows movement in the 3rd dimension reducing accuracy.

john
:)

dp
01-03-2011, 12:31 PM
Look at this picture on that Kitamura page. They have ground guide ways, which is consistent with my previous statement:

I still think it isn't schtick. It might be they have crappy castings and grinders and need to scrape, but I doubt it. I'm more inclined to think maybe there's union pressure.

Arthur.Marks
01-03-2011, 12:49 PM
If this thread is to evolve, may I suggest we begin to approach the subject as a comparison rather than a competition. I believe the majority of what I know on the two has been covered so far. Anyone more knowledgeable in the technical aspects of either process?

Personally, as an observer, I see scraping as becoming less common over time for the simple reason that it is quite labor intensive. In addition, abrasive processes made a significant leap forward in technology over the last 50 years. I do not mean to discredit the expert workmanship that is still required with abrasive processes. A machine, however, is a one-time cost. If the balance of production increase outweighs that cost, it is a clear choice. You can cut the hours/piece 1 to 1000, I am sure, in certain cases.

dp
01-03-2011, 12:58 PM
Forrest Addy reference in Wikipedia:

http://en.wikipedia.org/wiki/Hand_scraper

Follow ref. 3 at the bottom :)

The Wikipedia article repeats the same claim I think we all agree on to some extent and that is scraping in manufacturing is in decline thanks to precision grinding. I think too that contemporary machine design better allows machine grinding than machines built at a time when scraping labor was dirt cheap.

I think too that for the adventurous HSM machine rebuilder, scraping will continue to be common place. Many of us have more time than money to through at these older lumps.

Edit: Here's an earlier thread on the topic - not much has changed since:
http://bbs.homeshopmachinist.net/showthread.php?t=34116

Mcgyver
01-03-2011, 01:29 PM
If this thread is to evolve, may I suggest we begin to approach the subject as a comparison rather than a competition.

An excellent point, the skilled man knows how to do both and chooses which is best for the task at hand given the available equipment with the object is reduce time/effort and/or improve quality....just like the hss/carbide discussions where some guys sound like they're cheering for their team rather than taking an logical, reasoned approach to the decision.


Personally, as an observer, I see scraping as becoming less common over time for the simple reason that it is quite labor intensive.

Agreed, but also depends. I've seen lots of processes in China that would have been automated here eons ago...there its cost effective to through a body at it vs the capex of a machine and maintenance budget (how'd you like to bend the leads of a led over 90 degrees for a living?)

Its easy to say well just grind it. However go grind two large parts with several angle surfaces like a lathe bed and carriage so that they mate to a 10th. Maybe there's the odd guy and machine who claims they can do it, but its far from trivial....easier to get one part straight and scrape its mate.

A big fancy grinder accurate and straight with a head that can be angled can do one part, say a bed, such that the V's and flats are straight parallel and without twist. But this is so much less demanding if a certain latitude is there in height of the two flats relative to each other and the apex of the V, the angles of each of the 4 sides of the V to the flat etc......using a scrape-to-grind fit all that matters is that the 6 surfaces of the bed ways are parallel. You're right though, the trend is toward better and more accurate automated machines and eventually there'll be a grinder than can do it better and less cost.

The Chinese have arts such as carving and weaving where someone will work for decades on a single piece and you can still afford to put it in your living room. Given how often labour is the solution in China, vs automation, its almost surprising things didn't go the other way.....with cheap labour create an army of skilled scrapers turning out the highest end product that no one with a expensive grinder could compete with. Scraping itself isn't that difficult or complicated and the cost to set up a plant would be very low.

lazlo
01-03-2011, 02:11 PM
the skilled man knows how to do both and chooses which is best for the task at hand given the available equipment with the object is reduce time/effort and/or improve quality....just like the hss/carbide discussions where some guys sound like they're cheering for their team rather than taking an logical, reasoned approach to the decision.

Sure Mike, but I scrape, and you grind. So neither of us have a dog in this fight :)

You objected to Sir John's observation that scraping has been relegated to fitting and assembly operations on modern machinery, but that certainly seems to be the case:


John you've mistakenly come to the view that scraping is for a finish or oil retention; not the case. Scraping is for accuracy, often better than grinding

But as I stated earlier, hand-scraping is a fantastic opportunity for a HSM'er with the time, energy and patience to restore a beater machine back to factory alignment (or better!).

Forrest Addy
01-03-2011, 04:16 PM
I've scraped and I've ground and back in the day I was fairly expert at both.

Grinding is an inefficient process at best. The cutting tools are abrasive grains moving at high speed. Their cutting edges are malpresented to the work, pooly shaped for efficient cutting, and many of them are dulled subject to dressing technique and the condition of the dresser. All this combines to produce high flash temperatures at the cutting edge. The heated metal is instantly quenched by the coolant and the mass of the work adjacent to the surface film. Because the film is instantly heated and qunched it's under considerable tensile stress, whose magnitude depends on a number of the previouly mentioned factors.

This film, restrained by the underlying metal is under tension, causes the work to rainbow towards the wheel. Even a stress-free material is subject to deformation as a by-product of machine grinding. Ideally the work is surface ground on both sides to equalize surface stresses thus obtaining straight work. High precision apparatus such as a straight edge ground on the reference face will suffer some distortion no matter how carefully it's ground. The trick is to "preload" or spring the work an equal amount in the opposite if the grinding stress.

Machine ways can be surface ground to a high degree of precision provided the structure underlying the ground surface is stiff, plenty of coolant is applied over the entire workpiece to promote uniform temperature, the wheel is properly selected, run at the proper speed, dressed as appropiate with a sharp diamond, and the operator follows a careful plan of operations ensuring optimum conditions prevail over the grinding and finishing cycle.

Precision scraping is also an inefficient process but it does not involve high flash temperatures. While the cutting tool (the scraper) is quite efficient the process itself is manpowered and deliberative thus very slow compared to machining operations. Whether scraping or precision grinding is more accurate is almost a silly argument but it must be addressed. The resolution of the arguement is: "it depends" If the work lends itself to precision grinding, if there is a suitable grinder, if the grinder operator is skilled and experenced in way grinding, if etc. the grinding process is equivalent to precision scraping IF etc.

The difference is the character of the finish. A ground surface can be considered as continuous. A scraped surface as intermitant.

In a continuous finish in a tightly constrained bearing like a dovetail slide and the very low speeds at which it operates, the hydrodynamic oil film cannot form it's characteritic wedge. The oil still separates and lubricates and forms a barrier between mating parts but it's lubricaton mode is not barrier except at points of loading and it's not hydrodynamic: it's capilary thus elastic across the film thickness.

Consider a hypothetical dovetail slide accurately made with continuous surfaces bearing against mating continuous surface lubricated with oil and set to about 0.0008" clearance with the gib adjustment. When displaced along its single axis of freedom the other axes of freedom are constrained. Lateral loads applied at first squish a little oil out of one side and increase the clearance in the other. Depending on materials and speed of operation such an arrangement results in less than perfect lateral stiffness and when heavily load depend on nodal point loads where the algebraic sum of the loads coincide.

A comparable precision scraped slide bears on thousands uniformly but randomly distributed points each lubricated by oil in the surrounding undulatons of te surface. Move the slide 1/8" or 1/4" and an entirely new set of freshly lubricated points bear the load. Thus if scraped accurately and made stiff enough such a slide can be set up with less clearance without fear of failure and is thus by that difference, stiffer. It's this point to point (actually area to area) load transference and stiffness, orthodoxy tells us, that makes a scraped slide superor to ground.

My arguement is oversimplified and is limited to cast iron to cast iron slides. Fifty years of development and materials science has re-opened a technical arguement that may run on for future generations.

As a sepate issue: Someone made disparaging mention of a planer. I'm an old planer hand and let me give you the WORD. A planer that's level and in good condition can plane as accurately as most people can scrape. Problem is the planed surface (broad nose technique) is continuous and smooth as if surface ground and since the tool is efficient and free-cutting the surface is nearly tres free. It still needs to be broken up into bearing points by scraping. This operation triples the life of the slide bearings.

I once planed the table, saddle, and knee of a K&T milling machine. I exerted my skills and years of experience to perform the task. The scraper hand brought in to fit it only had to cross scrape the surfaces I planed for pattern and bearing and perform a little squaring and alighnment. Naturally we had to make new gibs, tweak the feed transmissions, lead screw brackets, etc. The flatness, finish, and all but the final fitting were accomplieshed on a planer in about 16 hours of machine time - about 1/3 the time for scraping if you look at time allowed tables dating from the 1950's.

I'm not a hero: what is did to reconftion that K&T, I've done before on other machine tools as have many others in the machinist trade of yore. What I accomplished on a planer was what used to be a routine operation for a planer hand and the very reason why planers were developed to such a high degree. I happened to have good training and progressive experience in machine tool way surface prep on a planer. The lore is fading from the industrial landscape and at age 69 I'm one of the dwindling number of its conservators. I wish I could pass it on but good planers are museum pieces not production floor equipment and people who can run them are dinosaurs.

Mcgyver
01-03-2011, 04:44 PM
No dog in the fight. Which is the best approach will depend....but I thought the point was good, its not a competition and learning is impaired if people start positioning as scraping vs grinding. Then again, what am i thinking, no one around here ever gets stuck on a point to a fault :D



You objected to Sir John's observation that scraping has been relegated to fitting and assembly operations on modern machinery, but that certainly seems to be the case:
.

:confused: to Sir John? the line you quoted of mine was directed at the OP, John, Jugs???.....that his post seemed predicated on scraping being done as a surface finish treatment rather to achieve a level accuracy which was what i was thinking of.

The 'often better than grinding' remark lives and dies on the 'often' .... whether its true or not is of course context dependent; man machine (or no machine)....but there are many examples in the home shop and industry where it will be the case.

The reason for mentioning it is this; any person experienced with grinding and scraping understands each's merits challenges and capabilities; lots of guys here in the boat for sure....BUT.....I believe there is a large group of who don't understand scraping and have little to no grinding experience who think that plonking something down on the grinder makes something as flat as flat can be. If one those guys wants to start to appreciate when & why of scrape or grind, understanding the challenges of grinding is important.

Its probably fair to say until someone has tried to get something really flat by scraping and grinding its hard for them to appreciate how difficult it is to achieve flatness. Flat is not trivial but there seems the erroneous impression from many that its easily achieve via grinding and but only painfully and archaically achieved by scraping. I know you know all that, but a lot of what I'm saying are generalities addressing the idea grinding = flat, scraping = self flagellation with a buggy whip. Of course with generaties come the exception reporting


But as I stated earlier, hand-scraping is a fantastic opportunity for a HSM'er with the time, energy and patience to restore a beater machine back to factory alignment (or better!).

not sure which one of us I'm quoting there :D....its very similar to what i said and 100% agree with you. You can get the worlds best shop that way; it does take enough effort and time though that you have to enjoy the journey, somewhat.

lazlo
01-03-2011, 04:51 PM
:confused: to Sir John? the line you quoted of mine was directed at the OP, John, Jugs???

OK, now I'm confused. Weren't you reply to Sir John's comment immediately above yours'??



Last time I was in China they were installing one of the latest Swiss slideway grinders for doing the beds on the CNC's.

It was on linear rails with a rack cut into the rail and the drive was by servo motor
John you've mistakenly come to the view that scraping is for a finish or oil retention; not the case. Scraping is for accuracy, often better than grinding



not sure which one of us I'm quoting there :D....its very similar to what i said and 100% agree with you. You can get the worlds best shop that way; it does take enough effort and time though that you have to enjoy the journey, somewhat.

LOL -- yes, I think we're violently agreeing :)

Mcgyver
01-03-2011, 07:46 PM
that was confusing...no my remarks were to John "jugs" the OP....they did follow me quoting jugs?? ya scared me, I thought it was the accumulated affect of the alcohol

.RC.
01-03-2011, 10:14 PM
the hydrodynamic oil film cannot form it's characteritic wedge. The oil separates and lubricates and forms a barrier between mating parts but it's lubricaton mode is not barrier except at points of loading and it's not hydrodynamic.



Is that a bit like a frog cannot climb a glass windows as it can get no grip as it is too smooth, but the frog can climb rougher wood easily...

The oil needs a slightly rough surface to grip to stop it from being squeezed out...

wierdscience
01-03-2011, 11:05 PM
This reminds me of the Gerstner video that was posted recently on PracticalMachinist where they proudly proclaimed that each drawer was hand finished. They actually had a guy who's full-time job was to sit down with a file and sandpaper and make sure each drawer, of every Gerstner box made, slid smoothly.

There were howls of protest that if they used modern woodworking machinery, that wouldn't be necessary, but it sure was quaint :)

Ya,and they would probably say the same about Steinway,but then there aren't any woodworkers over on PM so who really cares:)

J Tiers
01-03-2011, 11:06 PM
The issues, including the pics I posted, seem to come, as alluded to by mcGyver, from not thinking about the processes as they are done.

Grinding tends to be thought of as "heck yes it's flat, I surface ground it!". But all sorts of issues can make grinding come out "off" like the pics.... Experienced grinder hands know them.

But grinding tends to be an "open-loop" process.... if you do it right, you get a result within tolerance.... it isn't a check and re-do process.

On the other hand, scraping is very much a feedback process, every cycle is checked for accuracy, and the result is continuously refined. If you want it better, keep scraping (if the worker is competent). the limit is the reference tool, which can, by fairly simple (mechanically) methods be made as good as you want.

That difference is profound, and is, I think, being under-appreciated here

doctor demo
01-03-2011, 11:27 PM
As a separate issue: Someone made disparaging mention of a planer. I'm an old planer hand and let me give you the WORD. A planer that's level and in good condition can plane as accurately as most people can scrape. Problem is the planed surface (broad nose technique) is continuous and smooth as if surface ground.

The lore is fading from the industrial landscape and at age 69 I'm one of the dwindling number of its conservators. I wish I could pass it on but good planers are museum pieces not production floor equipment and people who can run them are dinosaurs.

Forrest, You will be happy to know that there is a job shop in southern Ca. that has a ''fleet'' of planers and they will plain custom shapes from stock either supplied by the customer or they will quote the job including material.

I can't find the link right now but I've talked to them last fall about a job I was bidding.
If memory serves Me right they can handle up to 12' lengths.

Steve

.RC.
01-03-2011, 11:39 PM
Here is a question I have been pondering...

How accurate is the average HSM grinder.... I am not talking about a Okamoto or like that but the 40 year old Brown and Sharpe or Norton or Jones and Shipman.

sansbury
01-03-2011, 11:40 PM
Perhaps not the facts but the passion of this argument comes back mostly to John Henry versus the steam hammer.

I suspect that if someone were to invent a robotic scraper that could meet or exceed the precision of any master hand, the process would rapidly lose much if not all of its cachet among enthusiasts.

Scraping is ultimately about building a machine capable of meeting certain performance specs. Many machine builders seem to solve the equations by other methods. IMHO that proves that the process is not necessary per se. It may still be that, for a given manufacturer with a certain mechanical architecture and workforce, that manual scraping makes sound economic sense. That would demonstrate its viability, but not its superiority.

J Tiers
01-04-2011, 12:05 AM
Perhaps not the facts but the passion of this argument comes back mostly to John Henry versus the steam hammer.

I suspect that if someone were to invent a robotic scraper that could meet or exceed the precision of any master hand, the process would rapidly lose much if not all of its cachet among enthusiasts.



I think that this is not true.

The reason is that I can, with an investment of relatively low $$ amount, obtain the tools to accurately create and assess scraped surfaces and alignments. With those, I can then refurbish, or in some cases do an "initial furbishment on", used machines, getting both enjoyable shop time, and a virtually new, or better than new, machine for a "sweat equity" investment.

The fact that the machine "isn't worth that" is almost the basic point.... if it was, it would neither need the work, nor be that cheap.

BTW...It's darn hard to type with a 20 lb maine coon demanding attention.... he has a head like a labrador, ramming it under my hands, and feet of competitive size tromping on the keyboard. "NO" is not in his keyword list.................

Juergenwt
01-04-2011, 12:19 AM
form change - Rolls trying to improve Chrysler parts.

Forrest Addy
01-04-2011, 12:26 AM
RC, your post #51: I don't follow your reasoning - not about the frog but the lubrication mode conundrum.

OTH I concede I worded the passage awkwardly. I know the concepts I'm trying to transmit but the words don't come out right. Old fartness, I suppose. BOLO for a revision.

Optics Curmudgeon
01-04-2011, 12:54 AM
OK, I've saved up a couple (three, actually) comments about the thread to date. First, in ye olden days machine parts were made in the production end, then sent into the "fitters", where they were scraped into proper fit and squareness. the best quality tools went through this process. Now, thanks to that earlier effort, we have mass produced machines that can turn out good product without the fitting stage, except in the most critical applications. There, the fitters still rule.
Second, woodworking gets short shrift when it comes to credit for precision, without realizing it many woodworkers are making parts to fit within .001 inch at times, often by...scraping!
Third, I have to agree completely with Forrest about planers, I ran one in my youth and they are poorly appreciated now. They were the standard for producing such things as lathe beds.

Joe

jugs
01-04-2011, 02:21 AM
As an apprentice toolmaker (100s of yrs ago):D I was taught how to scrape flat sliding parts, using hand & power scrapers (certainly a good lesson in skill & patience) & very useful for parts that were difficult to mount in a grinder.
After achieving a good fit we would usually lap the scraped surface with lead laps to remove the peaks & valleys caused by scraping, that allowed the oil film to wet the whole bearing surface without fear of point loading.

I also worked for Vandervell Products, makers of automotive components & the Vanwell racing car, designing & building production machinery.

this is how they did it

Flat & vee surfaces - most often induction hardened, always ground, sometimes lapped, occasionally scraped.

For cylindrical parts - no scrapers were ever used,

Depending on use,
Holes were either – bored, reamed, broached, ground, roller-burnished or honed.
Shafts were - ground, roller-burnished or lapped.

Gears were lapped using an abrasive slurry.

I understand that some lubricants need a microscopic matt finish (lapping) to adhere to, whereas others need close to a mirror finish, it all depends on the length & strength of the oil molecules.

The goal is to always get rid of the lumps & bumps to improve lubrication film over the largest possible area & thus reduce wear due to galling. An accurate flat but rough area wont stay flat for long.

Tip.
To lap the internal face of a scraped dovetail –
bend up a simple handle from some ¼” sq bar,
angle the dovetail slot so you can pour molten lead into it,
plug both ends with clay & press handle into clay so that it will get moulded into the lead.
Pour lead, when cool you have a perfectly shaped lap.
Use fine lapping paste on the side you want to cut, grease the other.

john
:)

.RC.
01-04-2011, 02:57 AM
RC, your post #51: I don't follow your reasoning - not about the frog but the lubrication mode conundrum.


I was wondering if oil behaves the same way as a blueing compound..

A bluing compound does not like transferring to a polished surface like a ground surface.. It won't stick to it... But a scraped surface as it is a bit rough, it sticks to it easily which a assume is because it has a rough finish...

In between two perfectly flat ground surfaces the oil film is the same thickness end to end... In between two scraped surfaces or a scraped and ground surface as the oil film does not have uniform thickness (as it fills the various pits on the scraped surface) I thought it might be more stable and less likely to squeeze out..

MuellerNick
01-04-2011, 03:41 AM
Is that a bit like a frog cannot climb a glass windows as it can get no grip as it is too smooth, but the frog can climb rougher wood easily...


That's a wrong picture.
The difference ground vs. scraped are the thousands of tiny reservoirs for oil. It's also the shape of these reservoirs that make the difference.
You could mill -a stupid idea, just for making clear the difference- thousands of small shallow cylindrical pockets into the surface. But they would have straight edges. Scraped reservoirs do have a very low angle -a wedge- that tremendously helps to pull oil "up the hill" when the guide is moved, even with only little distances.
The principle is similar to plain bearings that are not pure cylindrical/conical, but are a multiple surface bearing. Like in this video (http://www.youtube.com/watch?v=iJd8Zwd9L1k) at 6:30. These are much stiffer when rotating, because the oil is "pulled up the hill" and builds a considerable pressure on the "hill's top". Hydrodynamic.


Nick

John Stevenson
01-04-2011, 04:20 AM
Here is a question I have been pondering...

How accurate is the average HSM grinder.... I am not talking about a Okamoto or like that but the 40 year old Brown and Sharpe or Norton or Jones and Shipman.

Probably more related to how secure you can get the work, if using a magnetic table you probably get more errors from the pulling down than the accuracy of the grinder.

Earlier in this thread, JT I think it was shown a rectangular piece of metal ground then scraped to get flat.
That exercise would have been interesting if it had been repeated with a similar part held by it's sides in a vise on the sticky table, there are only 10 th's at play here.

Forrest Addy
01-04-2011, 04:28 AM
Nick, In my neck of the woods those oil reservoir intended to fred oil into the loaded zone are called "leads" and considerable theory has evolved to explain their best sonfiguration and merits. When done right in a scraped taper bearing as shown in Nick's video the clearance and configuration of the lead is separately adjustable and yes such bearings when run with the correct oil and oil delivery are very stiff and cool running.

Some are not. I'd characterize the spark-out time of the infamous Mattison tapered slotted plain bearing as "geologic". They are either spongey or prone to sieze and there is but two clicks of the bearing adjusting nut between one or the other. I hate it.

.RC.
01-04-2011, 05:20 AM
Probably more related to how secure you can get the work, if using a magnetic table you probably get more errors from the pulling down than the accuracy of the grinder.

Earlier in this thread, JT I think it was shown a rectangular piece of metal ground then scraped to get flat.
That exercise would have been interesting if it had been repeated with a similar part held by it's sides in a vise on the sticky table, there are only 10 th's at play here.

Ahh OK, so it comes down to workholding... The piece we are using as an example (the photo in that post) would be a bitch to attempt to hold in a vice due to it's length.. If it is anything like my experience with milling once you try to mill a long part that is much longer then the vice jaws then it just chatters like crazy...

If you have the right fixtures it would be easy, but given the tolerances we are talking about (tenths) I assume just mounting and dismounting all the various fixtures needed for accurate grinding would lead to inaccuracies as well if they are not remounted in the exact same position they were initially ground in at (as I understand you grind in fixtures when initially mounting them on the grinder table)

taydin
01-04-2011, 05:41 AM
Being a newbie machinist, I must be missing something very obvious ...

When the blue color is applied to the surface to be scraped and then a straight edge is moved over that surface, the blue color will be removed from the high spots and the low spots will retain the blue color. So the "hand" must work on the spots that don't have any blue on them. But all literature I read says that the high spots are the ones where the blue color remains? How is that possible :confused:

.RC.
01-04-2011, 05:52 AM
How is that possible :confused:

Easy, you don't put the blue on the part to be scraped...

You have it round the wrong way... The blue usually goes on the reference tool/part.. You can put a highlighter colour on the part to be scraped but that is to show the high spots more clearly when spotted..

J Tiers
01-04-2011, 09:00 AM
As for the oil and ground surfaces........ nice theory, might be true to an extent, in practice probably need not be an issue.

For starters, a lot of "American style" "hard" watchmaker's lathes had a hardened ground tapered spindle running in a hardened ground tapered bearing. For many years that was apparently the "standard of perfection". Jeweler's lathes are not , when foot-powered, exactly known for a high surface speed in the bearing, although certainly they are far faster than a crosslide, etc.

In any case, grinding, when it is good enough, is a lot faster and works really well on round things..... it's not easy to "scrape an item round", compared to scraping it flat.

And, it is less easy to "grind an item flat" than it is to grind it round.

if you want to produce a good surface to any particular standard, with minimal tools, scraping is your method, no debate, no argument.

The "goodness" is your option, since you can produce as good a reference as you want to have. You can achieve virtually ANY accuracy wanted, and that with tools you at least theoretically can produce yourself (it may take some time, but far less time than making a machine).

Spin Doctor
01-04-2011, 09:10 AM
Some are not. I'd characterize the spark-out time of the infamous Mattison tapered slotted plain bearing as "geologic". They are either spongey or prone to sieze and there is but two clicks of the bearing adjusting nuy between one or the other. I hate it.

The trick we always used on the Mattison was when we got to depth we would crank the Downfeed wheel up 2 to 3 thou. Then the machine would spark out. As to getting bleuing to transfer to a ground surface. When we would begin scaping the ways on lets say a Landis IW multi-wheel crank grinder we always broke the surface up by scraping the ways at 45D to the direction of travel from both the left and right so the direction of scraping was at a 90D angle to each other. Then we checked for high spots and alternated left and right when scraping. The first two scraping periods saved a lot of time.

lazlo
01-04-2011, 10:32 AM
Perhaps not the facts but the passion of this argument comes back mostly to John Henry versus the steam hammer.

I think that's a superbly accurate statement!

But that shouldn't preclude the HSM'er from picking up a sledge (scraper) if he can't afford a million dollar CNC bed grinder :) In other words, scraping provides an opportunity for a HSM'er to restore an old beater into a functional machine with nothing more than sweat equity.

For little stuff, like toolmaker's blocks, it's a much tougher argument, now that surface grinders are well within the price range of the average HSM'er.

Rustybolt
01-04-2011, 10:49 AM
20 years ago I was visiting Chicago Grinding.Theyhad a Matheson grindr that theyused to grind 12 foot steelyard.They had just had it rescraped. They claimed they could hold .001 plusorminus over 12 feet. Not too shabby IMO.

lazlo
01-04-2011, 11:09 AM
Here is a question I have been pondering...

How accurate is the average HSM grinder.... I am not talking about a Okamoto or like that but the 40 year old Brown and Sharpe or Norton or Jones and Shipman.

That's like asking how accurate is an old 10EE? :) How worn is it? What condition are the ways, the bearings?

But for reference, I bought a late-model Harig 6x18 for $1200. People are clearing out manual grinders...

Mcgyver
01-04-2011, 11:38 AM
You're all wrong, mostly, at least as far as the oil pocket lubrication part goes. :D

Scraping is scraping because it permits localized removal of material with a very limited depth of cut....this lets you make things very accurately....and that its comparative in nature makes achieving a near perfect fit easy. I think the surface that results is incidental; ie the methodology of scraping wasn't developed or embraced to form a surface finish it was done to accurately shape pieces.

Now, the surface that results from from scraping does have a pronounced surface variance. At a given viscosity of lubricant, provided the fluid is thick enough to maintain separation, a hydrostatic scraped bearing will move with less force than if the two surfaces were perfectly smooth. However, you could achieve the same results on the perfectly smooth components by altering the viscosity....and the perfect surfaces with the right viscosity would form a superior bearing because said layer could be thinner.

The reason lies in how the lubrication works in a hydrodynamic bearing. First off, the bearing works by the movement establishing an extremely thin wedge of fluid between the parts - the principal is at work in a journal or linear bearing. The fluid at the boundary layer (the solid part) does not shear against the solid part but tends to stay in place. The shearing takes place in the fluid - for a given viscosity, the thicker the gap, the less force required to shear. SO, with a variance in the surface such as results from scraping, much of the surface has a thicker gap which shears more easily. The irregular scraped surface has a net gap distance with a resultant force required to move the item...this could be replicated in two perfectly smooth surfaces via calculation and viscosity adjustment

A hydrodynamic bearing should never have metal to metal contact, rapid wear results. In effect, the viscosity should be chosen for gap at its narrowest (at the high points)....the enlarged gap between pockets gets a free ride with a much lower viscosity than is need for that gap, load and horizontal force.

I don't buy the irregular surface provides a place for the oil. If the oil is supposed to come out of the pockets to form part of the hydrostatic wedge, what replaces it? a vacuum? How come hydrodynamic journal bearings aren't given the same irregular surface treatment? As Forrest has said, its the wipers that supply the oil, not the depressions created by frosting.

From a lubrication point of view, tribology will tell you that the less variance the better and the lower the viscosity and closer the parts are together the better....you want the film to be as thin as possible and the best surface finish permits the thinnest fluid...with the limitation that if its too thin metal to metal contact will result especially if subject to vibration. Surface finish places limits here; rougher the finish, the greater the minimum film thickness required. So it seems the finish left by scraping is a detriment to ideal hydrostatic bearing conditions. Certainly I have not been able to find any bearing or tribology engineering texts that say a hydrostatic bearing is improved by an irregular or less than perfectly smooth and flat surface. In fact the inference is just the opposite; the thinnest layer is best and how thin a lay you can use will be limited by surface roughness and protrusions (which the high points after scraping are)

I see the reason parts are scraped in production is ease of manufacturing. It is one thing to be able to perfectly grind 6 or more angled surfaces perfectly parallel.....but it takes a very different machine and abilities to grind its mate so they fit to a 10th or better.....and since they are bearing surfaces they need to. Look around at the tools shops have; getting a bed reground perfectly is highly specialized work you send out to have done....because no one has grinders that can that. Yet even those shops do not try to grind the mating part to perfectly fit the bed! Scraping and/or various filler materials used. Advancements in machines and accuracy will eventually address that but its imo why one part is scraped to its ground mate, not because of lubrication.

dp
01-04-2011, 12:35 PM
Using 2"x2"x2" gage blocks as an example of very smooth, wringable surfaces: Place a drop of oil on one block, wring it against another block. At the end of the process the oil is, for all purposes, gone. The blocks are wrung fast to each other. Now frost one block, put a drop of oil in it, and wring it with an unfrosted block. No matter how hard you wring you will never wring all the oil out of the frosted block.

Obviously in the first example there will be a few oil molecules left behind after the wringing, so don't beat that point to death. It won't be near what is left behind by the second example.

Frosting both retains oil between the surfaces (can't be helped), and keeps it distributed equally at all point between two surfaces.

jugs
01-04-2011, 01:02 PM
You're all wrong, mostly, at least as far as the oil pocket lubrication part goes. :D
.................

I don't buy the irregular surface provides a place for the oil. If the oil is supposed to come out of the pockets to form part of the hydrostatic wedge, what replaces it? a vacuum? How come hydrostatic journal bearings aren't given the same irregular surface treatment? As Forrest has said, its the wipers that supply the oil, not the depressions created by frosting.

From a lubrication point of view, tribology will tell you that the less variance the better and the lower the viscosity and closer the parts are together the better....you want the film to be as thin as possible and the best surface finish permits the thinnest fluid...with the limitation that if its too thin metal to metal contact will result especially if subject to vibration. Surface finish places limits here; rougher the finish, the greater the minimum film thickness required. So it seems the finish left by scraping is a detriment to ideal hydrostatic bearing conditions. Certainly I have not been able to find any bearing or tribology engineering texts that say a hydrostatic bearing is improved by an irregular or less than perfectly smooth and flat surface. In fact the inference is just the opposite; the thinnest layer is best and how thin a lay you can use will be limited by surface roughness and protrusions (which the high points after scraping are)

..............

My sentiments exactly

Hence lapping/honing after scraping, to remove the 'decorative frosting' that some see as an end in its self.

I have seen so many machines that have worn the frosting away over the working stroke & are sill true & accurate over that area, but have a step ( the depth of the scraping)@ each end.
Lapping after scraping gives you the best of both worlds, Accuracy & a Reduced Wear bearing surface, although it does alter the cosmetic appearance which is important to some.

john
:)

pcarpenter
01-04-2011, 01:05 PM
Taydin-- you are not crazy. I posted a few times over recent years about using the "marking by removal" method and was treated as a heretic by most here, but some get it. Any method will work, but Edward Connelly, whose book is considered to be the bible on the topic by many, mentions this method and points out that it has the potential for a lot greater precision. He mentions using marking agents as thin as the haze left by alcohol wiped on the surface to be scraped.

The guy who taught me used a paste compound made of very fine titanium dioxide pigment mixed with just enough kerosene to produce a paste like shoe polish. In the old days it would have been white or red lead marking compound. You wipe it on the part being scraped and smear it out till it just leaves a very thin haze like wax on a car. I occasionally dampen the applicator pad with alcohol which helps it apply smoothly and flash dry quicker. You then rub the surface with the straightedge and cut away at the high spots which are shiny bare metal. I find that you get much greater "gradient" in the high spots this way as opposed to using the transferral method with blue. That helps you hit the high spots harder which can help you get there faster.

The other advantage is that when you are done with the scraping pass, you remove the swarf and this dry powdery stuff with a brush, stone it wet with kerosene, wipe clean and start over. I find it easier and less mess than a pasty mess made of hi-spot blue mixed with cast iron swarf. And, while your hands still get grey from the cast iron and titanium dioxide, you don't go in the house with blue on your nose and neck and a few toes you don't even remember touching :D

Still, both are just methods of differentiating high from low. As you noted though, the "instructions" change a bit depending on the marking method.
Paul

lazlo
01-04-2011, 01:23 PM
I'm pretty sure we're confusing scraping, flaking and frosting.

Scraping is the criss-cross scratches to make the surface flat.

The old timers have conflicting distinctions between frosting and flaking, but Connelly calls the half-moon patterns which are added for decorative purposes (and arguably oil pockets) "frosting." It seems like most modern scraping afficiandoes call the half-moons flaking. Biax calls their HM-10 model a half-moon flaker.

But in either case, flaking and frosting are applied in a separate step after scraping. On most of the machines you see in the last 50 years, the half-moon flaking is done on top of a ground surface, as on a Bridgeport, for example.


Hence lapping/honing after scraping, to remove the 'decorative frosting' that some see as an end in its self.

Scraped surfaces aren't lapped or honed after scraping.

lazlo
01-04-2011, 01:30 PM
By the way, while I was looking up the Biax model number for my Half-moon flaker, I noticed this description.

Add some gasoline to the fire :D


HM-10 Half-moon pattern, variable-speed electric model
(http://www.dapra.com/biax/scrapers/)
Applications: Scraping of half-moon oil-pocket patterns for slide way lubrication, or to break up friction and "stick-slip" on precision-machined flat surfaces and ways. Pattern creates pleasing appearance and ensures good surface lubrication with better wear characteristics. Rescraping of worn ways to reestablish lubrication and prevent further wear. Our "Flaker" or "Spotter" model.

jugs
01-04-2011, 01:40 PM
Using 2"x2"x2" gage blocks as an example of very smooth, wringable surfaces: Place a drop of oil on one block, wring it against another block. At the end of the process the oil is, for all purposes, gone. The blocks are wrung fast to each other. Now frost one block, put a drop of oil in it, and wring it with an unfrosted block. No matter how hard you wring you will never wring all the oil out of the frosted block.

Obviously in the first example there will be a few oil molecules left behind after the wringing, so don't beat that point to death. It won't be near what is left behind by the second example.

Frosting both retains oil between the surfaces (can't be helped), and keeps it distributed equally at all point between two surfaces.

As you say,
"in the first example there will be a few oil molecules left behind" that is the thickness of the lubricating film "The blocks are wrung fast to each other." a combination of thin film molecular attraction & air pressure - 5x faces 2"x2" = 20 x14.7psi = 294 lb , if you now put the blocks in a bell jar & pull a vacuum, the blocks will separate.

In the second example you will achieve metal to metal contact with much less effort, neatly demonstrating the breakdown of the lubrication film.

john
:)

Mcgyver
01-04-2011, 01:57 PM
\Hence lapping/honing after scraping, to remove the 'decorative frosting' that some see as an end in its self.



not sure about that, the reason is...i proffer...that with lapping it is very difficult to control where material is removed. The nature of a scraped surface is high spots; remove one set and you're resting on another - once you start removing some though, if its not via comparison to a reference flat (scraping), how do you know the new set is in the same plane? ....and if you lap them all out it very likely isn't in the same plane. Keep in mind a scraped surface is gone over with a stoned file or Arkansas stone which knocks of the most pronounced highs; the burrs.

I believe machine tool way design grew up in the context of the limitations of bearing point structure scraping creates ....things work because the surfaces are as big as they are and because the thin parts of fluid film holding things up are a small percentage of the overall area.

If you could make perfectly mating, flat and smooth surfaces i bet you could reduce the area significantly.


Frosting both retains oil between the surfaces (can't be helped), and keeps it distributed equally at all point between two surfaces.

Dennis, the hydrodynamic bearing absolutely needs replenishment and movement to create the fluid wedge. In your example though, the oil sitting in a depression doesn't prevent metal to metal contact of the high points and isn't necessarily available....a vacuum would be created if it was drawn out. I couldn't find in any engineering tribology text it discussed how surface depressions collecting oil benefit a hydrostatic bearing, quite the opposite. you'll find it in mechanical and machinist books maybe....but that imo is likely an erroneous conclusion someone reached that just keeps getting repeated....bearing design engineering and tribology engineering texts don't seem to support it. Obviously I'm no tribology expert, but the subject was of interests and with some reading I was surprised to learn how much in contravention of common practice the science seems to be...or i just read it wrong :rolleyes:

To make it a comparative example you would have to do the math and adjust the viscosity....the tribology stuff I've been reading says the smooth surface can be made to bear a greater load requiring less sideways force to move than the frosted.

dp
01-04-2011, 02:04 PM
In the second example you will achieve metal to metal contact with much less effort, neatly demonstrating the breakdown of the lubrication film.


When stationary, yes. So no wear. And since oil is incompressible, once the pockets are filled the migration of oil from the flat surfaces stops just the same as wrung unfrosted surfaces - that same molecular film is left. But once you start moving the pieces relative to each other, the oil is immediately picked up at all frosted locations on the mating surfaces. There is no metal to metal contact awaiting oil to be distributed from oiler ports.

I don't know about you guys but my machines spend a lot of time sitting which is equivalent to wringing the oil out. If they were expensive machines I'd be happy to know the oil pockets from frosting are in there and used immediately on turn-on.

Edit: Starrett says this about wrung gage blocks in a vacuum:

# When two very flat surfaces are brought into such close contact with each other, this allows an interchange of electrons between the atoms of the separate blocks, which creates an attractive molecular force. (This force will remain even in a vacuum or if no oil or water is present on the blocks.)

dp
01-04-2011, 02:23 PM
Dennis, the hydrostatic bearing absolutely needs replenishment and movement to create the fluid wedge. In your example though, the oil sitting in a depression doesn't prevent metal to metal contact of the high points and isn't necessarily available....a vacuum would be created if it was drawn out.

If all the oil between the surfaces is crushed out then yes, oil won't leave the pockets except as new oil migrates in. But all the oil is not crushed out from between the surfaces, so motion will redistribute between pockets what is still there (see the earlier discussion of the role of wipers).


I couldn't find in any engineering tribology text it discussed how surface depressions collecting oil benefit a hydrostatic bearing, quite the opposite.

Hydrostatic bearings require forced oil. For extended life this should happen even before the surfaces begin moving. Plane surfaces that are frosted are a special case of hydrostatic bearing in that the lubrication is never completely lost between runs.

Mcgyver
01-04-2011, 03:51 PM
Hydrostatic bearings require forced oil..

correct, typo on my part, I've meant hydrodynamic throughout what i wrote :o if i type hydrostatic, my bad, i'll correct it. if enough oil has be squeezed out so that you're metal to metal rapid wear will ensue; this is the case with two perfectly smooth bearings or the high points of a scraped surface. there is still metal to metal damage and oil in the pockets of the scraped surface won't get to the peaks; its not going to magically rise up leaving a vacuum in the hollow; there has to be sufficient oil, a layer; to keep the metal from touching whether its smooth or scraped to prevent damage

dp
01-04-2011, 05:06 PM
I don't think many HSM lathe aprons are so precisely fitted that this is going to be a factor. Using my own Grizzly lathe as an example I'd bet I have no better than 3-point contact across the full length of the ways. Ditto for the cross slide. My machines are a far cry from the precision designed into even a cheap hydrodynamic bearing. It's probably an ok rough analogy but in practice there are too many differences in how they work. My shaper ways probably come closest but they're somewhat self-lapping.

J Tiers
01-04-2011, 09:50 PM
If there is any lubrication benefit from a scraped or "flaky" surface, perhaps it is NOT AT ALL to do with some "reservoir" effect, but instead comes from a "turbulence" effect.

The uneven surface would create some turbulence in the film, which may help it not "break down", or squeeze out, or be dragged away.

sansbury
01-04-2011, 10:39 PM
I suspect that if someone were to invent a robotic scraper that could meet or exceed the precision of any master hand, the process would rapidly lose much if not all of its cachet among enthusiasts.

I think that this is not true.

The reason is that I can, with an investment of relatively low $$ amount, obtain the tools to accurately create and assess scraped surfaces and alignments. With those, I can then refurbish, or in some cases do an "initial furbishment on", used machines, getting both enjoyable shop time, and a virtually new, or better than new, machine for a "sweat equity" investment

Yes, you're absolutely right about that. My point was more directed at those who make a fetish of the process than those who rightfully use it in their own shop. Heck, scrapers (the machine) make no sense anymore in a commercial shop, but can be great for the hobbyist.

Here's another way to look at it. For years, one sign of a custom-tailored suit jacket was the presence of so-called "surgeon's cuffs" where the sleeves had real buttonholes. Since a tailor in a department store can't move buttonholes easily, they don't put "real" buttons on off-the-rack suits. There are a bunch of other little details like this that are held up as evidence that the suit is both expensive and well-made.

But nowadays, it is easy to go on the Internet and send your measurements to a guy next door to the mini-lathe factory and have him make you a suit for about the same price, or less. It will have the surgeon's cuffs, the fancy color lining, etc., but it's still be a cheap Chinese suit under all that.

That said, it's a cheap suit made to your size and color, style, etc., for about the same price as the off-the-rack one, so there's nothing wrong with that for what it is. Kind of like scraping.

MuellerNick
01-05-2011, 03:11 AM
Heck, scrapers (the machine) make no sense anymore in a commercial shop, but can be great for the hobbyist.

Well, that's your restricted tunnel-view of the reality.

There are companies that try to make their machines relatively cheap and use linear bearings. It is a known fact that they lack damping.
There are other companies that make high precision machines and they have no other choice than scraping.

A obvious example where you can't do without scraping (except you want to produce crap):
Lathe bed is ground to the nicest finish you can get. Now, you grind the saddle and you will never get full contact, because the slightest deviation of say the flat guide (a tad too high, at tad too low) will shift all contact areas out of being in full contact. -> Scraping. Even when using Turcite strips or Moglice or some such, that area has to be scraped to fit the ground bed.

Also, there has been done enough research around conventional guides in regard to stick slip, wear and friction. It always turned out that at least one side has to be scraped to get best results. Also fitting surfaces (column to base and such) do have better properties when scraped and coated with oil/grease before assembly. A factor of at least two compared to other manufacturing processes in regard to damping.


If those telling repeatedly the nonsense that scraping is useless, it is obvious that they never spotted a dovetail.

But this is a forum on the internet. So every Joe is free to tell his story. Even if he doesn't have the slightes experience.


Nick

Mcgyver
01-05-2011, 07:31 AM
My point was more directed at those who make a fetish of the process .

I wouldn't like to be considered an enthusiast or that its a fetish, that's I don't think a fair description. Its a technique that I know and that has its place. When someone who doesn't know asks, I try explain what I think I know about it, the when/where/why etc. I did the same with counterbores recently, does that make me a counterbore enthusiast? I can absolutely assure you I have no counterbore fetish :eek:

Ian B
01-05-2011, 08:01 AM
McGyver,

You say it's difficult to control where material is removed with lapping.

Johannson blocks are lapped to flatness and size, and as far as I can see, their surface finish and accuracy is about 100 times that of a scraped surface (give or take a bit).

The story goes that Carl Edvard Johannson converted his wife's Singer sewing machine into a grinder / lapper, and wifey helped out with the work. Cook dinner, iron some shirts, lap blocks of steel to a few millionths of an inch, do the dishes. And all this without complaining that her sewing machine had been swiped and hacked around by her husband the HSM'er.

Where do you find wives like this nowadays? :-)

Ian

J Tiers
01-05-2011, 08:44 AM
McGyver,

You say it's difficult to control where material is removed with lapping.

Johannson blocks are lapped to flatness and size, and as far as I can see, their surface finish and accuracy is about 100 times that of a scraped surface (give or take a bit).



A case of comparing apples to sociology......

A block needs material removed from a surface (or both), parallel to a given plane. The only control needed is the plane of operation, really, the rest is "removing tiny amounts", and "finish". Lapping can do that with ease.

A lathe bed, for instance, needs a minimum of 5 surfaces controlled for the carriage, which have a known geometry. of these , 3 are "non-adjustable", (4 of 6 if a double-V). If the bed is always the same dimensionally, within tenths or microns, the carriage could potentially be lapped by a controlled fixture. But the bed has small variations from unit to unit.

if the carriage were to be lapped on a "lap and try" basis vs the bed, to fit it to those variations on a particular unit, that would be converting the lapping process to a virtual analog of scraping. Except that one might well wish to scrape first to get very close before lapping.

In that way, the only arguable difference between the processes would be the exact means of removing the metal. Scrape, lap, sanding. angle grinder, whatever.

Lapping is NOT primarily capable of more than "surface refinement", because it almost by definition is not intended for removing even the small amount of metal that scraping can.

Milling removes gross amounts. Scraping or grinding remove smaller amounts (some grinders can easily go from raw to finish, I agree). Lapping refines a ground or potentially scraped surface.

lapping is not really suited for removing "this much" from "that spot". it is more for making 'this surface" conform to "that surface spec". Exactly where the material is removed is left "up to the process".

And the process for gage block lapping is a bit different from the process for lapping an injector pump piston....

of course if you adopt the "minilathe version" of lapping, which is to scatter coarse abrasive on the ways and rub the carriage over it, you can probably remove quite a bit. More than you want, probably, and from where you are not sure.

Mcgyver
01-05-2011, 10:44 AM
McGyver,

You say it's difficult to control where material is removed with lapping.

Johannson blocks are lapped to flatness and size, and as far as I can see, their surface finish and accuracy is about 100 times that of a scraped surface (give or take a bit).


Ian I don't know enough about gauge block lapping, how its controlled, what machines are used etc to make anything close an intelligent remark on their lapping.....

my comment was based on how I've done and seen lapping done which where a lap is charged and essentially use as an abrasive block to remove material from the work. Now when scraping, you're comparing your work via the blue to something flat (the premise is that is flat) and the markings give you very specific instructions on where to remove material to bring the work into the same level of flatness. Our only way of getting something flat is this comparison to something known to be flat....what other way is there? (within the typical resources of a home shop/small shop)

Its very specific, these instructions you recieve; in rough work work you're removing material from certain zones and not others and with finish work you're taking off specific points. I just can't see how lapping, as it might be done by one us, is going to give the same control.....wouldn't forgoing that control makes creating flatness by comparison challenging.

You could combine the two I suppose, blue to a standard and concentrate lapping to the specific high points....if the lap was very flat (scrape it :D) you might be able to bring regions down and create smoothness. Still it would seem hard to control what was removed....and I can't see how you'd control what part of say the diagonal on a dovetail you were removing from. They are often very small surfaces, 1/4" wide or so. It would be hard lap specific areas of something so small without producing a convex shape instead of flatness, ie rounding it over

Even if you have no further interest, its an exercise worth going through to see first hand how subtle it is bring something flat to surface plate quality - to make a accurate hydrodynamic bearings that's what the objective is. I don't want to sound like an enthusiast as Sansbury says, this is amateur engineering where decisions are based on rational and logic, but trying it out would bring perspective to why its so often advocated

Also, if its not broken, why fix it? its known, works, isn't that hard to figure out. My comments on scraping and hydrodynamic bearings were directed at the scraped surface erroneously being given positive hydrodynamic bearing characteristics compared to grinding. point being the stuff is scraped because it gets the job done not because it provides a better bearing surface.....but that doesn't mean there anything wrong with it as a bearing surface or that any pains should be taking to correct its surface as a bearing surface. When grinders are cheap that will make perfect mating complex parts easily (not a trivial thing I think), it will replace scraping in production; they're not they way they are now because of surface finish. Then again the idea might so entrenched the market insists on it.

Where I've used lapping is in cylindrical applications and it worked very well. i think in the round its self correcting; ie the lapp wears into a round shape as it also cuts the work. So far, flat lapping just hasn't been something I've needed much of. It would let you shape hardened tool steel but I've got a grinder for that.

gnm109
01-05-2011, 10:57 AM
Deleted.........................

dian
01-05-2011, 12:10 PM
i dont know much about this, but i wonder why the actual precision that can be achieved has not been discussed. for scraping it is limited by the accuracy of the master and probably by the thicknes of the blue. looking at the best commercially available straight edges (disregarding the price) and translating in to the size of a machine bed, it might not be so great compared to what can be achieved with grinding. what is the precision achievable with modern grinding machines?

MuellerNick
01-05-2011, 12:43 PM
what is the precision achievable with modern grinding machines?

The same as is available for the best commercial straight edges.



Nick

lazlo
01-05-2011, 12:54 PM
Lapping is NOT primarily capable of more than "surface refinement", because it almost by definition is not intended for removing even the small amount of metal that scraping can.

I'm not sure if you're thinking of a hand lapper? Surface plates, as one example, are rough ground and lapped. But it's a giant lapping machine that looks like a Blanchard grinder.

Here's a 24" power lap, that would be used for gage blocks or a small surface plate, for example:

http://www.youtube.com/v/3FGLUAuQy1k

lazlo
01-05-2011, 12:56 PM
i wonder why the actual precision that can be achieved has not been discussed. for scraping it is limited by the accuracy of the master and probably by the thicknes of the blue. looking at the best commercially available straight edges

Does anyone make commercial scraping masters/camelbacks anymore? All the scraping "straight edges" we're using are 50 - 100 years old.

Mcgyver
01-05-2011, 01:00 PM
Does anyone make commercial scraping masters/camelbacks anymore? All the scraping "straight edges" we're using are 50 - 100 years old.

sure there are, Busch precision and Challenge Precision are two that come to mind...better work some overtime though before ordering anything :)

lazlo
01-05-2011, 01:22 PM
sure there are, Busch precision and Challenge Precision are two that come to mind

I didn't realize Bush was still in business! If you go to their web page, most of their business is precision grinding :)

http://www.buschprecision.com/index.html

6600 Series - Dovetail Straight Edges (8)


BUSCH PRECISION Dovetails Straight Edges are widely used for checking the alignment and scraping in the dovetail surfaces of machine tool ways and slides. Made from specially treated, close-grained castings, these tools are finish machined and hand scraped to flatness accuracies of 0.0001 per 12” or better.

Spin Doctor
01-05-2011, 01:33 PM
what is the precision achievable with modern grinding machines?

Which are probably running on scaped ways, so if the attainable accuracy of the machine is dependent on the machines condition then we are still back to some guy making rough guestimates in his head on just how much material to scrape off and where. And yes the thickness of the Prussian Blue does make a difference. IMO most, no make that all inexperienced scraping hands use too much.

Arthur.Marks
01-05-2011, 01:42 PM
IMO most, no make that all inexperienced scraping hands use too much.

I had a machine that needed a gib re-fitted. When it was originally done, the gib was lengthened and now conflicted with final assembly. A guy was sent out to scrape the gib back in. I've looked at plenty of pictures of scraping online, etc. I've never had the inclination to try it myself. Worth mentioning, Spin Doctor, one thing that genuinely surprised me was the little amount of blue that was used. He also never re-applied so that by the time you got down to the final pass, it was extremely light. I did find that interesting.

I also was most surprised by the various tools used by this gentleman. He, of course, primarily used a traditional scraper, but the one that jumped out was sandpaper! :p He had a whole bag full of tricks---literally, like one of those electrician's tool pouches of different stuff. Nearly all the time it was the traditional scraping tool---but every once in a while, out came something unexpected and was quickly drawn across the surface.

This was all cast-iron, BTW.

.RC.
01-05-2011, 02:39 PM
Does anyone make commercial scraping masters/camelbacks anymore? All the scraping "straight edges" we're using are 50 - 100 years old.

Quite a few manufacturers in India and China..

lazlo
01-05-2011, 03:03 PM
Does anyone make commercial scraping masters/camelbacks anymore?
Quite a few manufacturers in India and China..

Really? Are they for sale outside China? That would be great!

.RC.
01-05-2011, 04:21 PM
http://www.alibaba.com/suppliers/cast-iron-straight-edge-supplier.html

http://www.luthraprecision.com/straight-edges.html#cast-iron-straight-edges

http://www.jashmetrology.com/camelback_type.php

lazlo
01-05-2011, 04:59 PM
http://www.alibaba.com/suppliers/cast-iron-straight-edge-supplier.html

http://www.luthraprecision.com/straight-edges.html#cast-iron-straight-edges

http://www.jashmetrology.com/camelback_type.php

Wow! Is there a Western retailer? The scraping folks here would go nuts if you could buy inexpensive camelbacks, prismatic references, etc.

I wonder why Shars/CDCO doesn't carry these? Target audience too small?

J Tiers
01-05-2011, 08:17 PM
i dont know much about this, but i wonder why the actual precision that can be achieved has not been discussed. for scraping it is limited by the accuracy of the master and probably by the thicknes of the blue.


The master can be made as accurate as you want it to be, you just proceed with the 3 plate process longer.

Blue is not used for the ultimate..... it is the slight haze left by evaporating alcohol on the surface. The marks are slight polished places.

As for the power lapper...... Obviously that machine is incapable of use as a scraper is used, however much it takes off. Wrong size, wrong shape, too small, and too large, too, depending on what the "target" is.

Power lapping machines tend to be not so much "lappers" as "hones" or "grinders".

Chinese straight edges?

Are they made to the "nearest metric equivalent" of "flat"? :D

.RC.
01-06-2011, 12:47 AM
I would not trust any cast iron product I bought to be perfectly flat when it arrives, no matter where it came from..

oldtiffie
01-06-2011, 01:19 AM
Why is it that when I read some of the diatribes
http://www.thefreedictionary.com/diatribe

from some of the pro-scraping Evangelists that I keep linking or associating it with the Sermon on the Mount:
http://en.wikipedia.org/wiki/Sermon_on_the_Mount

The burning bush:
http://en.wikipedia.org/wiki/Burning_bush

The Ten Commandments:
http://en.wikipedia.org/wiki/Ten_Commandments

Revelations:
http://en.wikipedia.org/wiki/Book_of_Revelation

Now how about Exodus?
http://en.wikipedia.org/wiki/Book_of_Exodus

Being a bit less evangelical about scraping would be a good start.

dp
01-06-2011, 01:49 AM
Being a bit less evangelical about scraping would be a good start.

Nothing works as well as a fresh coat of thick skin. Who, btw, is evangelizing? Is that what we call enthusiasm now?

oldtiffie
01-06-2011, 02:09 AM
Dennis.

As the "pros" (for) are and have been in the ascendancy for sometime and given that few of them are going to change their minds anyway, the "anti-es" may not change too much either and many others have either given it away or developed a "ho-hum" attitude and have more or less faded away.

A lot of others don't even bother to respond at all.

It has become a forum limited to a few by disinterest and attrition.

I have an open mind about scraping but its not top of the list of things I like to do - but I will do it if it is is the only viable alternative. Otherwise I don't bother.

If my machines weren't working as they should or as I needed them to I'd consider scrapping or scraping.

There is not a machine in my shop that can't do its job as I need (as opposed to want) it to.

Other than my surface and T&C grinders, there is not a machine that I can't replace with new under $2,000 and a 90km (~55 miles) road trip.

I am not at all interested in scraping for the sake of it and it will only be done on an occasional "only if essential" basis otherwise.

I have no issue with others who like or have to scrape jobs.

Forrest Addy
01-06-2011, 03:01 AM
I wasn't that fond of scraping when I was fit to do it and I'm less fond now that I'm old and brittle. The only thing that attracted me to scraping is that it was the only way I could work to the necessary tolerances for machine tool rebuilding without having access to a zillion dollars worth of high precision machine tools and measureing apparatus.

And I don't think anyone in his right mind could accuse me of being an evangelist on any topic. For one thing I equivocate too much. For another I can come up with viable alternatives for almost any situation at the drop of a hat.

I teach the basics of precision hand scraping because by default I'm a conservator of a fading craft deserving perpetuation. Since I have a talent for teaching, I wish to pass my knowledge onto those who wish to refurbish their machine tools and reference equipment. Hopefully they will pass their skills on to others. I make no bones about how in precision hand scraping there is no substitute for hard work, persistance, patience, planning, and intelligent application of method to the problem. Precision hand scraping is not fun; OTOH there are rewards that very few can appreciate.

To me, precision hand scraping is merely this: a system of refinement of fits and finishes to very close tolerances by means of hand tools, traditional skills, and modest testing apparatus. There's other ways of perfecting surface reference tooling and resurrecting machine tools but most involve considerable expense. Precision hand scraping is about the only method I can think of where a home shop guy of limited budget and lots of spare time can acquire the wherewithal for that selfsame resurrection. Thus, precision hand scraping is a practical means to a practical end; not a sacred calling or a focus for obsession.

Them that say nay to precision scraping and deny its efficacy are either not listening or drowning the dialog by ranting misconceptions. If they don't wish to gain knowledge of precision scraping and its application then they should probably not participate in a discussion of scraping. I mean, it's a free country and freedom of speech and all that but why add to the noise level?

John Stevenson
01-06-2011, 04:32 AM
Why is it that when I read some of the diatribes
http://www.thefreedictionary.com/diatribe

from some of the pro-scraping Evangelists that I keep linking or associating it with the Sermon on the Mount:
http://en.wikipedia.org/wiki/Sermon_on_the_Mount

The burning bush:
http://en.wikipedia.org/wiki/Burning_bush

The Ten Commandments:
http://en.wikipedia.org/wiki/Ten_Commandments

Revelations:
http://en.wikipedia.org/wiki/Book_of_Revelation

Now how about Exodus?
http://en.wikipedia.org/wiki/Book_of_Exodus

Being a bit less evangelical about scraping would be a good start.

Being a bit less evangelical about asinine Tiffiepedia links would be a better start.

oldtiffie
01-06-2011, 04:36 AM
I think you've got it pretty well Forrest.

Scraping is no more than a skill or resource and is a means to an end and is not a/the end in itself or any sort of rite of passage or Holy Grail either for Machinists or anyone else.

When people get a bit too fervent about anything to the extent that they are devotees or obsessed about it ("Holy Rollers"?) they "lose" me.

If those who like and/or need to scrape as a means to an end to make a machine or tool fit for its intended purpose need any encouragement they will get plenty from me.

It is far too easy to intimidate or coerce people and to polarise a discussion.

Everybody on this BBS has exactly the same rights and obligation as and to any other. In that context, rank, time of joining or numbers of posts are irrelevant.

A bit less fervor - and on occasions, vitriol - and a lot more open-mindedness particularly toward newer members will go a long way.

I use basic skills and tools as my preferred option always and scraping is in that list - as an option. I start at basic and work upward until I have the skill and tools I need and there I stop.

If I never saw or heard of a scraper again I would not regret it, but as it is highly probable that I will have to scrape a job on occasion I will do it and be glad I've got the skills to do it.

J Tiers
01-06-2011, 08:42 AM
I wasn't that fond of scraping when I was fit to do it and I'm less fond now that I'm old and brittle. The only thing that attracted me to scraping is that it was the only way I could work to the necessary tolerances for machine tool rebuilding without having access to a zillion dollars worth of high precision machine tools and measureing apparatus.


To me, precision hand scraping is merely this: a system of refinement of fits and finishes to very close tolerances by means of hand tools, traditional skills, and modest testing apparatus. There's other ways of perfecting surface reference tooling and resurrecting machine tools but most involve considerable expense. Precision hand scraping is about the only method I can think of where a home shop guy of limited budget and lots of spare time can acquire the wherewithal for that selfsame resurrection. Thus, precision hand scraping is a practical means to a practical end; not a sacred calling or a focus for obsession.


Perzactly..........

I haven't seen this as a debate, or a contest. Some others may have.

Tiffie, as our self-appointed "voice of reason" might even be ignoring those who have been trying to paint the method as an old, outdated useless "buggy whip". if anything, they have been the ones actively proselytizing.

The rest of us have been answering the initial question: "Scraping... why?"

A buggy whip doesn't do you much good when you have a Maserati, but it comes in pretty useful if you have a horse and buggy.

On the other hand, if the horse picks up a stone, or throws a shoe, it generally won't help at all to stop at a gas station..........

Mcgyver
01-06-2011, 09:00 AM
Tiffie, as our self-appointed "voice of reason" might even be ignoring those who have been trying to paint the method as an old, outdated useless "buggy whip". if anything, they have been the ones actively proselytizing.

The rest of us have been answering the initial question: "Scraping... why?"
.

exactly, my head hurt after those last two OT posts. Its a like a drunk Yoda who doesn't like scraping smacked me in the head....I think I need to lie down


A lot of others don't even bother to respond at all.

It has become a forum limited to a few by disinterest and attrition.

I have an open mind about scraping but its not top of the list of things I like to do - but I will do it if it is is the only viable alternative. Otherwise I don't bother.

If my machines weren't working as they should or as I needed them to I'd consider scrapping or scraping.

There is not a machine in my shop that can't do its job as I need (as opposed to want) it to.

Other than my surface and T&C grinders, there is not a machine that I can't replace with new under $2,000 and a 90km (~55 miles) road trip.

I am not at all interested in scraping for the sake of it and it will only be done on an occasional "only if essential" basis otherwise.

I have no issue with others who like or have to scrape jobs.

lazlo
01-06-2011, 10:40 AM
Power lapping machines tend to be not so much "lappers" as "hones" or "grinders".

That was exactly the comment I made to Paul -- lapping is a specialty form of grinding. A power lap is basically a very, very precise blanchard grinder.
Gage blocks are lapped in a power lap exactly like that.

I've never seen how they lap surface plates, but I'd imagine it's a supersized version of the same thing.


Chinese straight edges?
Are they made to the "nearest metric equivalent" of "flat"? :D

:) I wouldn't expect them to be remotely flat as shipped. But then again, any of the 50 year old camelbacks I've bought on Ebay weren't remotely flat either.
In the blacksmithing community, they refer to Chinese anvils as ASO's: "Anvil Shaped Objects". These would be CSO's.

But you'd think that even if they're made with the same crappy cottage cheese scrap iron that's in my Chicom vises, it's still make a decent reference with some work.

lazlo
01-06-2011, 10:43 AM
I wasn't that fond of scraping when I was fit to do it and I'm less fond now that I'm old and brittle. The only thing that attracted me to scraping is that it was the only way I could work to the necessary tolerances for machine tool rebuilding without having access to a zillion dollars worth of high precision machine tools and measureing apparatus.

Forrest, as usual, you nailed it! I think that's the perfect summary of the pros and cons in one concise statement.

Rustybolt
01-06-2011, 12:14 PM
I've never seen how they lap surface plates, but I'd imagine it's a supersized version of the same thing.


I've only seen it done once. On a surface plate big as a double bed. They brought in another surface plate just as big, charged it with lapping compound and the started lapping. As I recall it took a few days to get where they wanted it. Didn't look all that much fun.

dian
01-06-2011, 12:31 PM
still, what is the precision achievable with grinding/lapping today?

i have two din 874/00 bevelled straight edges (4 x 10^-6 minimum) and if i check them against each other i cannot detect any irregularities. so i reckon, they are straighter than that. now here we are talking about a massproduced item costing under 100 $. what can be achieved with maximum effort?

on the other hand the camelbacks i can buy are 874/0 (8 x 10^-6) at best (although i have seen a grade 0 somewhere from a us supplier, which i believe works out to 5 x 10^-6.

as to the three-edge-method: who is really goin to do it and when do you know when to stop and how accurate it is? of course you could have them checked by modern methods, but at what cost?

Bob Farr
01-06-2011, 12:48 PM
*** I teach the basics of precision hand scraping because by default I'm a conservator of a fading craft deserving perpetuation. Since I have a talent for teaching, I wish to pass my knowledge onto those who wish to refurbish their machine tools and reference equipment. ***

Forrest,

I'd like to improve my machine refurbishing skills past the rather low 'clean, repair, paint, adjust and lube' stage which I'm in now. I have a couple small machines which could benefit from a more thorough approach. When and where will you be offering your next scraping class and how do I sign up?

Thanks,

Bob

lazlo
01-06-2011, 12:56 PM
I've never seen how they lap surface plates, but I'd imagine it's a supersized version of the same thing.

I've only seen it done once. On a surface plate big as a double bed. They brought in another surface plate just as big, charged it with lapping compound and the started lapping.

When I was shopping for a surface plate, I called the local metrology shop, and they had X price for measuring the accuracy of your surface plate, and Y price to lap it to virtually any accuracy. I.e., they would lap your surface plate to AAA grade accuracy, if you paid them. This is a small shop, so I'd love to see how they're doing it...

.RC.
01-06-2011, 02:56 PM
Other than my surface and T&C grinders, there is not a machine that I can't replace with new under $2,000 and a 90km (~55 miles) road trip.



But having seen the machines H&F sells for a little bit of extra hand work they can be turned into a decent machine.. My experience with cheap machines the fit between mating parts leaves a lot to be desired..

A couple of examples with my machines was on the lathe the tailstock would change it's position between clamped and unclamped due to a poorly machined base..

On my milling machine you could not tram the head then tighten the bolts as again the head would move as you tightened the bolts...

For a few hours work I repaired both with the scraper.. And as an added bonus chatter was reduced markedly in the milling machine..

http://img.photobucket.com/albums/v606/OzRinger/bpclonescraping005Custom.jpg

oldtiffie
01-06-2011, 04:02 PM
Thanks .RC.

That is pretty well just the point I've been making.

The job needed to be done and the only real option was scraping and you got on and did that well to the degree necessary - same with your vise (recent post).

So far as I am concerned, scraping for the sake of scraping or for
"looks" is a waste of time and energy, but, as is the case with your job, it was necessary and you had the necessary references, hand and power scrapers and skill and got on and did it.

Scraping is no more than just a skill and a process just as marking-out, screw-cutting, making gears, turning, milling, off-hand grinding, drill-sharpening and Shop Maths etc. etc. are. They need to be learned, worked at and improved and maintained to the degree necessary.

Fitting and Machining is just another Trade - same as Carpenter, Plumber, Brick-Layer, Boilermaker-Welder, Electrician, Motor Mechanic etc. etc.

They are Trades. Those that practice them are Tradesmen.

They are not professionals - but Doctors, Engineers, Architects, Chemists, Dentists (who have University Degrees are) etc. are - when they are working in their profession but they are only machinists when they are working as machinists.

Scraping is "Trade" work with varying degrees of skill.

The skill levels are matched or developed and only need to be used to the degree necessary for the machine or part to perform its intended use and purpose.

Scraping is not some mystical black art from the past, as it is only a process that needs to be learned and given the way everything can get very dirty it is a black-hands job (that can take some cleaning-up!!).

Spin Doctor
01-06-2011, 04:56 PM
Then why is it we never hear someone say they are "a practicing plumber". We assume he knows what he's doing. Where as professionals are always practicing. Makes you wonder when they are going to get it right. :rolleyes:

PS yes I know the differences in the use of the word practice.

.RC.
01-06-2011, 05:09 PM
So far as I am concerned, scraping for the sake of scraping or for
"looks" is a waste of time and energy,

I agree, but do people do that?

dp
01-06-2011, 07:28 PM
Scraping for appearance is somewhat like painting for appearnce. All you need is basic Navy battle wagon grey, but some things just look better when the craftsman adds a bit of care. There's nothing wrong with machines and methods that please the eye. That little red hit and miss engine posted here a few days ago didn't need the pain but it sure looked good with it bright shiney red. Many have heard 'chrome won't get you home' but once you've got your machine well tuned and accurate what harm is there in embellishing it?

I don't care what others might think about it, this is a damn nice looking machine! ;)

http://www.flickr.com/photos/67292116@N00/4010206475/sizes/l/in/photostream/

A classic car is just a clean old car. A junker is a dirty old classic. The difference is eye appeal.

jugs
01-06-2011, 07:33 PM
oldtiffie
So far as I am concerned, scraping for the sake of scraping or for
"looks" is a waste of time and energy


I agree, but do people do that?



Yes, that's why I started this thread :D :rolleyes:


Other than for decoration what’s with this obsession with scraping/ flaking/fish-scaling.

In days of old when machine beds were planed – (leaving long score marks) & shafts/bearings were turned/bored with single point tools –( giving a microscopic ploughed field finish) with accuracy’s of a few thou & dubious lubrication, it was necessary to smooth off the high spots by scraping.

Now we have modern machining methods that can give surfaces measured in microns instead of thous, you have a perfectly machined / ground /honed surface, why on earth would you want to destroy the bearing surface & the accuracy by scraping ???

I’ve heard it said (by people that should know better) that "it improves lubrication, as the oil sits’ in the hollows".
In fact what happens is as a load is applied, the crests can break through the oil film & rub against the opposite surface causing wear. The hollows do provide a handy place for small grit particles to mix with the oil to give an effective grinding paste.:eek:


Lubrication is always best served by large areas of smooth (fed by a few well placed big oil feeds) faces, so the oil film is NOT broken by crests & hollows.



john
:)

oldtiffie
01-06-2011, 08:30 PM
Thanks Jugs and .RC.

I don't mind a bit of "spit and polish" (ex Navy) when the occasion and the job warrants it but never for doing more than is necessary to get the job done.

Scraping seems to one of several topics where some seem to have a "pretty profound religious experience" and others seem to have a profound sexual experience (aka "wank") - some seem to have both.

Perhaps some need to get their heads out of the clouds and also get their feet firmly (im?)planted on (in?) the ground.

I was going to say that some need to "get a grip" but it may be that is more part of the cause and less of a cure (I nearly said "solution").

ABEC bearings are similar to scraping in that regard.

I suggest that the exotic and erotic solutions be left alone and just address scraping in the context of an average HSM - and not a "production" or "commercial" - shop/set-up.

lazlo
01-06-2011, 08:33 PM
The story goes that Carl Edvard Johannson converted his wife's Singer sewing machine into a grinder / lapper, and wifey helped out with the work. Cook dinner, iron some shirts, lap blocks of steel to a few millionths of an inch, do the dishes. And all this without complaining that her sewing machine had been swiped and hacked around by her husband the HSM'er.

Neat story! Some how I missed that in all the fuss :)

gnm109
01-06-2011, 08:55 PM
Thanks Jugs and .RC.

I don't mind a bit of "spit and polish" (ex Navy) when the occasion and the job warrants it but never for doing more than is necessary to get the job done.

Scraping seems to one of several topics where some seem to have a "pretty profound religious experience" and others seem to have a profound sexual experience (aka "wank") - some seem to have both.

Perhaps some need to get their heads out of the clouds and also get their feet firmly (im?)planted on (in?) the ground.

I was going to say that some need to "get a grip" but it may be that is more part of the cause and less of a cure (I nearly said "solution").

ABEC bearings are similar to scraping in that regard.

I suggest that the exotic and erotic solutions be left alone and just address scraping in the context of an average HSM - and not a "production" or "commercial" - shop/set-up.


This may be heresy. I was led to believe that every machine must be perfect or no parts could be made....that's true, isn't it? :)

dp
01-06-2011, 09:28 PM
There are circumstances I think we're all prepared to recognize on sight and that is when somebody puts lipstick on a pig. In the case of frosting or flaking that would be where copious amounts of either or both are put on places that will never see another mating surface. This seems to happen a lot on ebay machinery as an attention getter or to conceal a swayback lathe or mill, and surely there are people out there who don't know it for what it is. Those people probably don't mind lipstick on a pig or what the fuss is.

I know of at least one biker who creases his chaps. There's no accounting for some people's tastes.

J Tiers
01-06-2011, 10:14 PM
This may be heresy. I was led to believe that every machine must be perfect or no parts could be made....that's true, isn't it? :)

Well, if the machine is messed-up, and you have to fix it, by scraping, grinding, etc, you have a choice....

You can do a half-assed job, and be faced with repeating it later..... Or you can put it to bed with a good quality job, done once and lasting a long time.

Perhaps that second choice is "perfection", but if something is worth doing, it's worth doing it to the best of your ability. Particularly if you will reap the benefits for a long time to come.

oldtiffie
01-06-2011, 11:34 PM
Well, if the machine is messed-up, and you have to fix it, by scraping, grinding, etc, you have a choice....

You can do a half-assed job, and be faced with repeating it later..... Or you can put it to bed with a good quality job, done once and lasting a long time.

Perhaps that second choice is "perfection", but if something is worth doing, it's worth doing it to the best of your ability. Particularly if you will reap the benefits for a long time to come.

And that is getting to the nub of the whole scraping and other like processes JT - just as Jugs, the OP and .RC. - pretty well said.

The job is either a long, medium or short term fix and the work required of it will determine the necessary work/scraping to be done to get the machine back (to?) an optimum condition for the work it has to do - no more.

That means knowing what those limits are based on an objective assessment - with no subjective idealistic "pie in the sky" stuff.

Next is marshaling the tools and skills required. The skill level will have to be at least the minimum required.

Next is to decide how long the machine can be out of action and how much time and when can be alloted to a reconditioning job that may well take a lot of time all of which may delay the job even starting let alone finishing.

These pull-apart and (re)put-together jobs take a lot of floor space, resources and time - as well as money.

This path has been a "path of sorrows" for many over-enthusiastic and under-skilled and under-resourced "do-er upper-ers".

It can be your own Via Dolorosa ("path of sorrows") as you carry own cross of your own making toward your own stations of the cross and your ultimate (self?) crucification - with a hoped-for resurrection.
http://en.wikipedia.org/wiki/Via_Dolorosa

After I've done the appraisal, I decide whether the machine/tool is worth doing up at all or whether I leave it "as-is", make the best of it and junk it and buy a new one.

The "junk it and buy a new one" is my preferred and default position unless there are compelling reasons otherwise.

J Tiers
01-07-2011, 12:29 AM
'at's fine, Tiffster.....

In my case, it is best to cut to the chase......

The machine isn't usually "down for repairs", generally in my hands it hasn't been "up" yet, 'cause I just bought it, for a low price, KNOWING I'd have to do work, and having developed a rapid estimate of how much and what type.. After buying a couple dozen used machines of various types, one can do that fairly accurately.

Skills? 'Ow d'yer think usn's GIT them skills? Prize for the little boy in the back...yes we git's 'em by DOING the work. Nobody yet ever developed any skills by setting around waiting for the "anointing of the holy scraper" to descend upon them......

Most every one of the machines has been pulled apart, refurbished in either a rough and ready 'git it workin" or fix it right mode, and then used.

I did run out of steam on a shaper..... I'll finish it, but meanwhile, I just don't NEED a shaper bad enough to keep on it.

But a mill that will be the vertical mill for the shop, that I can and will spend time on to get it right.

Buying new? I've got to where that's almost like cheating...... I restore old engines, in the process of which I restore old tools. When not working on engines or tools I am the model shop/prototype shop for work as well. One day I'll probably build some small engines for myself, but I've enough work in the shop to keep me happily busy. If one thing bores me for now, I've another to work on.

Machine fixing is not an obstruction to me, its as good shop time as making a little engine that is of no particular use, making replacement parts for a bigger engine, or making proto parts, repairing stuff around the house, etc.

Face it, you've admitted that you don't hire out your services, so nothing you do in your shop is essential as your living, etc. So one thing ought to be as good as another to work on....... That's how I see it....

BTW, WHAT DO you do in your shop? You have a couple T&C grinders, presumably lathe, mill, etc........ I reckon you don't just polish those things...... let us in on the secret. You've seen what many of us do

Forrest Addy
01-07-2011, 12:34 AM
Yup, that's the key Tiffie. New machine or used, old, or decrepit, you start witn a whole machine tool survey where every attribute, defect, feature and control is tested, documented, and evaluated.

In a complex item like a machine tool you have to start with the basics and build up to a plan of work. Anything less and your just another shade tree jerk-off ripping off parts and stacking them up, making in the end more work that is necessary, losing parts and information, jumping to conclusions, and very possibly screwing the equipment up forevermore.

There an orderly process to everything; shrewd people plan their work and work their plan whether it's planning for retirement, caring for the folks when they get old, housetraining a pet, making a sandwich, or re-conditioning a lathe that could be in better condition.

ZZ 502
02-02-2017, 11:39 AM
In a nutshell, everything starts with the flat plane. The best way to create the flat plane from which all flat surfaces that follow is scraping. There is one book that will calibrate all on the topic of scraping vs. grinding. The title of the book is "Foundations of Mechanical Accuracy" by Wayne R. Moore. This book explains it all. It was written in 1970 and is available from the Moore Machine Tool Company. There are probably PDF versions online someplace. Read this book. I guarantee it will enlighten all who do, and it will likely change the way you think and work. Thanks.

Charlie