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Peter.
11-01-2012, 04:23 PM
I recently bought a benchtop round-column mill (Warco WM15), with a mind to convert it to cnc operation. My plan is to first fit up the x nd y axes with steppers, and keep the round column with manual, then stepper controlled quill downfeed. I will fix the head in alignment by keying the rack to the column. Later I will change the round column and head for a square steel column I have waiting, fitted with linear rails to carry the z carriage.

Anyway, I have stripped the base to machine for fitting the ballscrews and found quite the horror-story of an assembly. Some faced are scraped quite well and others hardly touched. Some bear all manner of gouges and grinding marks - some of the work has even been done with the edge of a disc cutter blade. I knew these things are supposed to be poor in quality control, but take a look at these pics and see.

http://peterrimmer.myby.co.uk/images/warco1.jpg

http://peterrimmer.myby.co.uk/images/warco2.jpg

http://peterrimmer.myby.co.uk/images/warco3.jpg

http://peterrimmer.myby.co.uk/images/warco4.jpg

Peter.
11-01-2012, 04:24 PM
http://peterrimmer.myby.co.uk/images/warco5.jpg

http://peterrimmer.myby.co.uk/images/warco6.jpg

http://peterrimmer.myby.co.uk/images/warco7.jpg

http://peterrimmer.myby.co.uk/images/warco8.jpg

I can't in all conscience continue with the build with what I have here, and have been unable to find anyone local to look at it so I've decided to learn the basics of scraping and try to bring the machine to some semblance of reasonable operation. Right now, the table and cross-slide bind well before the ends of travel unless I back off the taper gib adjuster a long way.

I've placed a wanted ad for scraping tools, and got some scrapers on the way from that. I have a small 6" surface plate of unknown quality (left by my late father) and a small tube of spotting blue and I'm looking for a larger granite plate. I've also started to machine a piece of cast iron for the dovetail vee gauge which seems to be 60.5 degrees according to my non-vernier protractor.

So this thread is to document my adventures into the black art of machine scraping. I figure that with only 150 invested in the hunk of Chinese junk, even if I make a complete mess of it there's no great loss. I'll document a much as I can and take on board any advice and criticism with equal enthusiasm.

BigJohnT
11-01-2012, 04:30 PM
MullerNick has some pretty good youtube videos on scraping...

John

Peter.
11-01-2012, 04:42 PM
I've watched Nick's videos, and some others John. I'm also working my way through Connely's book but I find it hard going concentrating on a 500-page book when all I want to do is get hold of some tools and just have a crack at it myself.

Mark Rand
11-01-2012, 06:01 PM
If you've still got a VHS video player and a telly to connect it to, PM me a snail mail address and you can have my copy of Michael Morgan's scraping video and book.

regards
Mark

BigJohnT
11-01-2012, 06:02 PM
I know what you mean Peter, I have a compound on my Samson lathe that needs some attention and I have the tools, just need to find the time.

John

Peter.
11-01-2012, 06:09 PM
If you've still got a VHS video player and a telly to connect it to, PM me a snail mail address and you can have my copy of Michael Morgan's scraping video and book.

regards
Mark

That's very generous Mark. I don't have a VCR in the house but I'll see if I can find one to borrow.

quasi
11-01-2012, 06:52 PM
What is a VCR?:D

Erik Brewster
11-01-2012, 07:05 PM
A few tips:
- You will need a good way to sharpen your carbide scraper. That means diamonds. I started with a diamond lap. The ones with the little dots. It just didn't work. I have since moved to an accu sharp. Just sharpening on the stationary disc on the bench was a huge improvement over the DMT. Silicon carbide (green) grinding wheels don't work. I hear they micro chip the edge of the carbide. I don't know how true that is, but I can tell you that an edge that is beautiful to the eye isn't sharp, so maybe there is something to that.
- You don't need a 60.5 degree straight edge. Any angle smaller than that will do. Just use it as a flat on one side, and tilt it up to use it as a flat on the other angle of the dovetail. It is only important that the mating angles fit well. That is ensured by using one side of the slide to spot the other.
- The big challenge isn't scraping (though that takes some learning). It is measuring all the big and strange geometry. Be VERY sure your measurements are correct. It's a bad day when you discover one of your measurements was off and you have to scrape your way out of it.
- Start scraping something flat that isn't your mill. You will mess it up, and you will appreciate you didn't mess up your mill. Then scrape something to a geometry other than flat (right angle?). That will get you a feel for the challenges of scraping your mill. It only needs to be a few square inches to get a feel for it, so it shouldn't take more time than you need to understand things.
- Don't think you can judge the quality of a scraping job by eyeballing it. It can be as crooked as a pretzel and still have pretty scraping marks on it. The worst looking stuff can be straight. You never know until you get the bluing out.
- Beware of false bluing patterns. If the surface makes a V shape, when you blue it, you will rock it on either side of the blue, making it look better than it is. Make sure to hinge the part to avoid false blue patterns.

Good luck! I'm looking forward to seeing your progress.

Forrest Addy
11-01-2012, 09:25 PM
Scraping a whole machne tool so all the axes are linear and mutially perpendicular isn't hard but it does require practice, care, and sequential procedure.

Scraping, like any machning process, is subtractive: you remove (scrape off) all material projecting above the surface you wish to establish.

My suggestion is you develop your scraping skill and collect the basic equipment. The skills you can acquire by taking a class in the basics, finding a mentor who will teach you, or find books and videos you can self teach from. As for the equipment,some you buy, some you make.

Care has to do with the standards you set from your self. The temptation is cone you find how easy it is to scrape small areas flat very close limits (tens of millionths) is to try to make the whole machine absolutely perfect. You have to be practical and set a budget for component contributions to overall accuracy. This sounds frightening by it's something that almost takes care of itself if your order and sequence of operations are practical and well-wrought.

Focus early in the game on Connely's remarks on the procedure for scraping-in mating dovetail slides and how you check progress. No one check will tell you all you need to know about the fit of a dovetail way bearing to its mate. Most osf the time you need to take several check and follow their indications to final accuracy.

If you ensure that all way bearing pairs are closely fitted and linear, the motion of the pairs are mutually perpendicular your re-scrape will be successful. If you get the spindle correctly aligned to the coordinate system represented by the way bearings your CNC retrofit will be far more satisfactory in terms of size holding, rigidity, and productivity than a plain bolt-on kit.

The final problem is gib fitting. I see the machine is equipped with tapered gibs. Scraiping may remove more maerial than the gins can adjust for. You can either insert a shim behind the gib (lame but effectve) on make a new fitted gib (PITA and better buy maybe overkill) Gibs are a PITA to make or they are not-that-bad depending on your approach. When the gibs are properly fitted the machine wiil be a dream to operate.

The gaping porousity in the photo is a good place to any of the popular filled epoxies. Flush out the oil with and agressive ssolveny, blow dry, dress the sharp edges, and syringe in the epoxy so it fills from the bottom. Do this early in the scraping cycle.

Mcgyver
11-01-2012, 11:17 PM
pretty rough. Is it new? I would have guessed someone other than the factory did this; ie doubt the factory scrapes, but that is just a guess. I did a mini mill x/y and the bearing surfaces were as the dovetail cutter left them. yuck.

the last few issues of the magazine has a detail account & instructions on scraping a mini mill x/y set up

Peter.
11-02-2012, 03:39 PM
Some great advice which I thank you all for.

Erik - I saw in one of Mullernick's vids he had made a custom vee-way gauge for a strange angle, that's where I got the notion of making one. I am going to make a diamond lap from a spare motor and chunk of iron. I'm also fortunate enough to have some small (4x3x1/2") pieces of cast iron I bought a while back on a whim. I plan to scrape these for practice.

Forrest - as ever I place the greatest weight on your comments and advice.
I had thought about what I hope to achieve from my work, and decided that if I can get my slides working full travel with an even amount of sticktion and no slop I would be well pleased whatever the apparent finished condition. Certainly, I'm not aiming for tolerance in the tenths right now. If I find that I have an affinity for the work I can always go-over it when my skills are more developed, if not - well I'll just live with the results or pay someone to rectify my mess. I'm sure it won't come to that.

Mcgyver - I don't know who did the scraping, I assumed it was factory. I bought the machine used for 150 but I don't think it's used much at all - just been around a while.

Peter.
03-04-2013, 08:37 PM
Just revisiting this thread to let you all know I made my first effort at scraping today. I had intended much sooner but had a nasty accident with my hand and cut a tendon and some nerves, so I've been unable until now to use my left hand fo rmuch.

So I took this piece of cast iron I had lying around and cleaned up one side with a file and emery and spotted it with some blue on my granite plate. Clearly I need to work on my bluing as it went on too thick, but I figured it was a good enough indicator as it was, so I started scraping it.

http://peterrimmer.myby.co.uk/images/scraping (1).jpg

http://peterrimmer.myby.co.uk/images/scraping (2).jpg

http://peterrimmer.myby.co.uk/images/scraping (3).jpg

http://peterrimmer.myby.co.uk/images/scraping (4).jpg

Peter.
03-04-2013, 08:47 PM
Things were quite frustrating at the beginning. I figured that I was holding my scraper at too steep an angle, so I adjusted that. I was also still struggling with the blue. I was applying it with a paper towel - need to get a roller - and it was very sensetive to how much I put on.


http://peterrimmer.myby.co.uk/images/scraping (5).jpg

http://peterrimmer.myby.co.uk/images/scraping (6).jpg

http://peterrimmer.myby.co.uk/images/scraping (7).jpg

http://peterrimmer.myby.co.uk/images/scraping (8).jpg

Peter.
03-04-2013, 08:51 PM
Very hard to get consitant readings with so much to learn at once - you can read up all you like but until you get your hands on a scraper and actually start doing it you don't realise how many things have to work to get a half-decent result. I paid more attention to grinding the scraper without a burr and used it very flat with lighter weight and started doing a little better. I realise these are first tentative steps and I've a long way to go, but it was quite satisfying when I was stoning the burrs off and started to have the stone stick to the work - really made me feel I was getting somewhere.

http://peterrimmer.myby.co.uk/images/scraping (9).jpg

http://peterrimmer.myby.co.uk/images/scraping (10).jpg

So that's where I'm at now. 3 hours into my first piece of scraping. All critical comments gratefully accepted :)

lazlo
03-04-2013, 09:00 PM
You're getting there Peter -- keep at it! :)

Are you rotating your scraping 90* on each pass?

Peter.
03-04-2013, 09:10 PM
Yes I am rotating it, except right on the corners where I can really only run off onto the corner. I can really appreciate how fine a job you must do on getting the scraper edge keen now too - I have some 9-12 micron diamond paste on order but for now I'm using a diamond cup wheel to keep the edge.

The spotting isn't coming along as well as I hoped. I find that I am moving the spotting around after every scrape instead of increasing the spots per inch. I am using quite a light pressure on the scraper - could that still be too much or is there another flaw in my technique?

loply
03-05-2013, 05:59 AM
Peter, I'm a relative newbie to scraping but as I'm just a little bit beyond you in the learning curve my experience may be helpful.

In terms of simply 'moving the blue around' you may need to be careful not to scrape away all of the blue - your scraping marks should be next to each other but with a gap between them. If you scrape the blue entirely then you will flip-flop the contact areas, rather than increasing the PPI. Leave some blue standing but try to 'split' each area up.

Also, don't scrape too light. You won't get anywhere. I sometimes spent hours achieving nothing because I wasn't raising any dust. Just scratching around not doing anything particular. If a scrape doesn't leave a little pile of dust at it's end you haven't done anything but scratch the blue off.

Cheers,

Erik Brewster
03-05-2013, 08:37 AM
You should be scraping somewhere in the the 0.0002" - 0.0005" deep range. This is pretty easy to see by putting the part on a surface plate and sweeping an indicator across the scraped surface. You will see the individual scraping marks as deflections on the indicator. If you don't get the scraping deep enough, you won't get oil pockets that are functional. In addition, it will take forever to remove any material, if you aren't scraping deeply enough.

You said your blueing is moving around every cycle. Is it consistant if you do multiple spottings without re-scraping? If your bluing isn't consistant, your scraping will be pointed in the wrong direction.

Peter.
03-05-2013, 08:53 AM
Yeah I'm struggling with the bluing. Tomorrow I will stop by the craft shop for a couple of ink rollers. I have found that thinning the blue even slightly makes it spread nicely but also transfers in one solid patch on the work. Un-thinned I have to work at it to get an even coating on the plate then it lasts just a couple of spottings and I have to re-apply, and invariably it goes on either thinner or thicker. Still, nothing worth having comes easy I guess.

Mcgyver
03-05-2013, 09:27 AM
what kind of blue are you using? colour reminds of permatex which I find a pita....strong preferance for Dykem high spot. do not dilute. I like using a folded over piece of felt to spread it, never had an issue of it being too thick. you just put less on. the diamond paste will help, when the scraper isn't sharp you get lots of chatter marks....you need to build a cast iron lap and you'll have terrifically sharp scrapers

Erik Brewster
03-05-2013, 09:39 AM
What are you using for blue?

I use a cheap foam roller for rolling the blue. I'm sure there is a better option, but that works. Also, make sure that you don't have any dust in the blue. I rub the blue with the side of my hand to make sure I clear any grit or dust. I also use my hand as a gauge to feel for dust. It should feel flawless, or there is more cleaning to do.

I do this every spotting.

This brings up the type of blue. I use canode water based blue because it is easy to clean and it works. I can't even imagine the mess that oil based blue would make.

rowbare
03-05-2013, 10:05 AM
You are coming along nicely. When you start with new part, it is a good idea to do one or two passes on the whole area to establish a consistent scraped surface. That will get you through the tool marks and the work hardened skin. The rest of the scraping seems to go more smoothly after that, you don't get that sort of skidding feeling every time you hit something that hasn't been scraped yet.

bob

Peter.
03-05-2013, 10:21 AM
I'm using 'Micrometer Engineer's Blue', which is now called Stuart's Micrometer Blue according to Google but my tube is donkey's years old by the looks of it. I found it in a tool shop and thought it was layout blue until I realised it didn't dry.

I might try some of that Canode blue because I had a lot of fun cleaning myself up last night :)

loply
03-05-2013, 12:07 PM
Peter,

I have a tin of that stuff but I ordered some Dykem HiSpot after some time. The Dykem is a lot more opaque and therefore easier to see, and generally seems easier to work with. I got a small tube off ebay for a few quid.

Rich

lazlo
03-05-2013, 02:35 PM
You should be scraping somewhere in the the 0.0002" - 0.0005" deep range. This is pretty easy to see by putting the part on a surface plate and sweeping an indicator across the scraped surface. You will see the individual scraping marks as deflections on the indicator. If you don't get the scraping deep enough, you won't get oil pockets that are functional. In addition, it will take forever to remove any material, if you aren't scraping deeply enough.

Here's a picture of the Master himself checking for "Chicken scratches": :)

It's pretty amazing to run a dial indicator across a gauge block you just scraped to 40 spots per inch -- it bounces like you're indicating braille. Moore mentions this in Foundations, that this is why all the photos show them using a flat lapped piece of tool steel on their scraped surface plates to take measurements:

http://i164.photobucket.com/albums/u15/rtgeorge_album/Scraping%20Class/IMG_4194.jpg

loply
03-05-2013, 03:28 PM
If I'm measuring a scraped surface I lay a small, hardened and ground parallel on it each time to average out the scrape marks.

If you don't do this you'll be chasing your tail as you'll merely be measuring the scrape marks, not the average plane.

Spin Doctor
03-05-2013, 05:47 PM
What are you using to dull the surface of the work. Seeing as how red lead is pretty much unavailable in the US I'm wondering what you are using in the UK. We used to use something called Gear Compound. Our inspection dept in in the Axle Division used for checking contact on Ring and Pinion sets. When we couldn't get Red Lead any more we switched to that. Worked reasonably well. Later I started using Denatured Alcohol. Just a small amount to dampen a lint free rag wiped on the surface. Too much and the cooling from evaporation could really mess with your results. This dulled the surface just enough that the Hy-Spot really jumped out. It does look like you are strating to get the hang of it. But then I've seen scraping jobs seemingly go to hell in a handbasket just when you thought you were getting close. When that happened it seemed it always came back in pretty quick and we'd be pretty much done.

Spin Doctor
03-05-2013, 05:49 PM
http://i164.photobucket.com/albums/u15/rtgeorge_album/Scraping%20Class/IMG_4194.jpg

Is that a Fellows Gear Shaper I see in the backround. Yes I believe it is.

lazlo
03-05-2013, 09:16 PM
Is that a Fellows Gear Shaper I see in the backround. Yes I believe it is.

It is indeed -- good eye. Nate had 4 - 6 of them, IIRC.

I posted a thread about the whole 40-hour scraping class on PM, but the pictures are here, including a bunch more of the gear shapers:

http://s164.beta.photobucket.com/user/rtgeorge_album/library/Scraping%20Class

Peter.
03-05-2013, 09:30 PM
Thanks for that Lazlo, it's nice to see other novices' work to compare my own with. Looks like most are getting a better depth of removal than myself.

Doubt there will ever be a scraping class over here in the UK :(

Spin Doctor
03-06-2013, 05:54 AM
Looking at the pics on 'bucket one of them does not bring back fond memories. Scraping the bearings on press frames and large rotating fixtures. We used pull scrapers made from heavy files (12" or larger) with two other file pieces cut off and welded on for handles set vertically. The blade was surface ground to get rid of the file teeth and the scraping edge was free hand ground with a large radius on a pedestal grinder and an oscilating spindle grinder* with an edge on both sides. Later we tried flat scrapers with a large bull nose radius on the blade. it worked but then they moved all the presses out.

Peter.
03-09-2013, 06:36 PM
I've done a few more hours today. I decided to start over by fly-cutting all the sides of the block. I did my best to get all the surfaces square to each other, I hope it's not too far out. I then started re-scraping that face again.

I started picking up deep scratches in the surface when scraping heavily and thought that this was due to picking up material out of the surface of the cast iron block but later discovered that it was due to me leaving a burr on the side of the scraper tip when sharpening on my diamong wheel - despite running the wheel away rom the outside edge. Once I figured that out I gave it a single swipe both sides flat on my oilstone and afterwards not only was it not making grooves but it was cutting a lot better and more controllably too.

Using the ink roller had made a huge difference to my bluing and it's getting a lot more consistant now. I put a dollop of blue on my little surface plate (which needs scraping, incidentally), and roll some out on there then just use what's on the roller to replenish the big plate's blue.

Question: I find that if I put the work down on the blue it will slide a couple of circuits then 'suck down' onto the plate. Is this normal? I can still slide it but with a lot more stiction. If I roll the blue out thinner it's much less inclined to grab but then I can hardly see the blue spots.

My intention is to get a pretty good even spotting on this side of the block, then survey the other side with a surface gauge then scrape that side in whilst also trying to get it co-planar with the first side. Should be a lot of fun :)

I aslo need to make my diamond lap.

Erik Brewster
03-09-2013, 09:39 PM
Good to hear you are improving!

The sticking happens when the plate gets very flat. If your scraping isn't deep enough, it gets bad, fast. Good lighting is your friend when you are looking at those faint patterns.

Are you pivoting the part to make sure you are getting good contact? The gist is to put the part on the surface plate and push gently on one side. It should pivot 1/3 of the way from the opposite side (assuming it's a flat plate weight distribution). The push on the other side. It should pivot 1/3 from the previous side. If it is pivoting in the middle or on the end, you are sitting on a high spot. This test will keep you from scraping a cylinder. If you have a cylinder (very large radius) and you spot it, unintentionally rocking it, you will get a great blue pattern, but you will not have a flat surface...

Peter.
03-09-2013, 11:06 PM
Well something else I'm doing wrong. I have been grabbing the work either side with each hand and making a couple of circles on the plate.

Thanks Erik.

blondguy
03-10-2013, 03:04 AM
Peter, could you be so kind as to post up some photos of your scraper(s) & perhaps your honing rig? I would like to try scraping but right now I really don't even have a mental picture of the equipment involved.

thanks much

Erik Brewster
03-10-2013, 03:46 AM
Well something else I'm doing wrong. I have been grabbing the work either side with each hand and making a couple of circles on the plate.

Thanks Erik.

I don't know if you are doing it wrong :) the pivoting is to make sure it's sitting flat. I do it on every spotting cycle - it only takes a few seconds, once you get used to it. It is completely different that spotting (transferring the blue). The circles are fine if you have the part sitting flat and not on a high spot.

Peter.
03-10-2013, 08:01 AM
Peter, could you be so kind as to post up some photos of your scraper(s) & perhaps your honing rig? I would like to try scraping but right now I really don't even have a mental picture of the equipment involved.

thanks much

I'd be slightly embarrassed since my setup is quite crude and basic. I bought a handful of scrapers that were supposedly 'new and unused' only to receive three somewhat rusty hss scrapers and two home-made carbide ones, also rusty, which were carbide tips brazed onto some flat bar. Luckily, the tips weren't affected by the rust on the shank.

I use one of these to sharpen all my carbide stuff. I was a little concerned about the cheapo cost but I've been using it a couple of years now with no sign of it wearing out. It quickly lost a bit of 'bite' but that's normal with diamonds and once it settled down it gives nice consitant grinds.

http://www.ebay.co.uk/itm/151006492344

Richard King
03-10-2013, 10:41 AM
It makes me proud reading 2 of my "kids" teaching scraping as they promised. Thanks Robert for the photo bucket pic's. That was a great class. I sure wish the 2nd one could have happened..but Nathan was to demanding...on having everyone scrape his machines only. Erick I will be out in the Bay area again this spring with DH. He has found a machine shop to hold the next class. For you UK guys I have my DVD on demand now, to save the price of mailing overseas. The DVD shows everything Erick is saying. It follows the info I teach in the classes. I sure wish I could come to the UK and teach some classes. Plus take a vacation. I would love to go to Ireland too. Take care and if you ever need any info please write me. I will help anyone who has a rebuilding or scraping problem. I have been answering some questions on here too. If you search my name you should be able to find the posts I talk about scraping and I just posted how to scrape a gib yesterday. Thanks and Happy Scraping. Rich

http://www.indie-ondemand.com?vidid=39506&oid=474

Peter.
03-10-2013, 02:10 PM
Richard if it weren't for people like you, Forrest and others doing the teaching and contributing online then people like myself would be floundering in the dark, probably not even prompted to try at all. I cannot than all you guys enough.

Peter.
03-14-2013, 04:08 PM
Having tried (and failed) to take any useful readings with my cheapo mag base with bendy post and half-thou indicator I've scoured the local area and managed to buy these. All used stuff, apart from the Mitutoyo DI.

Mercer heavy indicator base with rock-solid inch diameter post. Came with a Baty half-thou indicator.

http://peterrimmer.myby.co.uk/images/dials1.jpg

Swiss-made Sylvan digital half-tenth indicator
Mitutoyo 1uM dial indicator
Verdict .0001" DTI

http://peterrimmer.myby.co.uk/images/dials2.jpg

Got them for a super-knock-down price, new would be too much for me to even consider, but they are all in good condition except the verdict needs a service.

Hardly compares with the shelves-full of good stuff I see member have collected here but you gotta start somewhere and stuff for scraping seems to be very hard to come by around these parts. No luck at all finding any kind of straight-edge yet.

Mcgyver
03-14-2013, 04:58 PM
good stuff Peter, that is one solid looking indicator base.

Peter.
03-14-2013, 05:24 PM
It's very nice to use. Do you know what the bar is for that is in the top right corner of the box? It clamps across the top (or bottom) of the base using the tee-slot and has some ground faces on it.

loply
03-14-2013, 05:27 PM
Peter,

I watched eBay and Google for a straight edge for 6 months and not a single one came up.

In the end I googled for engineering or machine tool companies and started phoning around asking if anybody had one they didn't want or would be willing to sell. First two phone calls yielded two hits! Visited a guys workshop and he had about 10 collecting dust. Ended up getting a nice British made 36" knife edge, paid good money for it mind, but as you say they are hard to get.

I envy that set of indicators!

Cheers,
Rich

Mcgyver
03-14-2013, 06:16 PM
It's very nice to use. Do you know what the bar is for that is in the top right corner of the box? It clamps across the top (or bottom) of the base using the tee-slot and has some ground faces on it.

what you've got is probably more correctly referred to as a comparator - a dial indicator is set up with the plunger pointing downward and parts are placed between the base and plunger for measurement. mainly a quality control thing, lets you check a lot of parts quickly. My guess is the piece you asked about is a table that would go on the base with work sitting on it. It can't think of a reason why it won't make a solid and good indicator base or surface gauge and it also has the comparator function....maybe one thing missing, it doesn't have the fine adjustment a surface gauge has.

Peter.
03-15-2013, 08:40 PM
..maybe one thing missing, it doesn't have the fine adjustment a surface gauge has.

Luckily I have an adjustable stem that I got with my lathe. I'll make a clamp to fit it to the stand. It'll save a lot of fiddling trying to zero the dials.

Having used my newly-aquired dial gauges to survey a part, I now have some questions:

I find that the dial jumps about a couple of tenths when running it across a scraped part, even after de-burring with a stone. I take it this is normal? If I make a clamp for the digital gauge will this be more comfortable to read over the scraped surface?

Having de-burred, part-scraped and surveyed the cross-slide of my chinese benchtop mill (the one at the top of the thread) I find that with the face of the Y-axis dovetails sitting on the surface plate, the X-axis dovetail is approx 0.0015" lower one end than the other. This is much better than I expected if I'm honest but I still want to put it right. My question is, how do you decide whether to scrape the x-axis down a thou and a half one end, or scrape one side of the y-axis down? Both still need work.

Peter.
03-16-2013, 11:25 PM
Tired of trying to find a bevel straight edge I decided to try to make one from a sash weight I have kicking around. I brought four of these home one day, two larger and two smaller. This is one of the larger pair which machine very nicely. The two smaller ones were harder than a Moss Side bouncer and impossible to cut so I threw them in the scrap. Hope they didn't break the scrappy's frag machine :)

Cut one edge flat. My machine has limited capacity so I had to cut and move the part, which isn't ideal since this machine is one of the reasons I want to learn scraping.

http://peterrimmer.myby.co.uk/images/sash1.jpg

Clamped 1-2-3 blocks to the bed and clamped the part to those to square off one side:

http://peterrimmer.myby.co.uk/images/sash2.jpg

Mounted it to my tilting table to cut a 40-degree bevel. Hope it doesn't bend like a banana when I finish it tomorrow. If it comes out straight i'll scrape one side and see how it looks:

http://peterrimmer.myby.co.uk/images/sash3.jpg

Richard King
03-17-2013, 09:38 AM
A couple of Days ago I got an Email form a guy asking me about scraping a small machine to mae it a CNC...at the time I didn't add 2 + 2. Then yesterday after "Pete" from .org uk sent me a drawing of a compound slide I figured it out and I sent him a link to this thread asking if he was Peter. LOL and said Yes, so I asked him if we could continue here...and he again said Yes.

When I first saw those photo's it reminded me of a Rung-Fo mill a neighbor asked me to help dismantle and carry it into his basement. It had that same sort of crap scraping and ground ways, angle grinder that is...

I hope Peter's hand is healing up and if he is hand-scraping he will give his hand plenty of exercise.
I re-read this post yesterday and want to make some suggestions right away that should help him and the other readers improve there scraping. First thing that needs to be said is I do not think my scraping technique is the only style out thier and several people can scrape all over the world so I don't want to spend any time arguing with anyone about who's ink or technique is better. I will not waste my time answering those sorts of questions. As they say "This is not my first rodeo"

I want to help Pete and everyone else who wants to learn my technique. But, in reality it isn't my technique, I did not invent it, I learned it and have adapted many techniques I have been taught or observed in my 62 yrs. I learned to scrape from my Dad who was taught by a German Immigrant to the USA durring WW-2. . Over the years I have worked with Journeymen scrapers from Switzerland, Poland, UK, Italy, Japan and of course here in the USA and we all did the same cross hatch or X pattern scraping and our scraping depth was the same; .0002" on average. We all used some sort of ink and applied it in the same basic way.

We all used a bubble level and some sort of device that resembled my Dad's invention the King-Way. What I am saying, the professional scraping community is small and we all scrape in the same way. I have always said I do not care how you scrape as long as you and I are getting the same quality in the same amount of time. I have taught for over (sometimes hard to count, it's been so many) 20,000 people in 35 or 40 years where I have taught others that did not work for my family's Rebuilding Company where I taught men to scrape too, prior to teaching my first class at GM in Indianapolis In back in the early 1980's. I used to and still do tell my students "If your not completely satisfied with what I teach you you don't have to pay me or I will refund your fee" I have always been paid.
Ok..to your part.

Richard King
King-Way Scraping Consultants
10855 68th Street South
Cottage Grove, Minnesota (MN) USA 55016
651 338-8141
handscraping.com
Richard@handscraping.com or KingRich1@aol.com

lazlo
03-17-2013, 10:04 AM
Tired of trying to find a bevel straight edge I decided to try to make one from a sash weight I have kicking around.

Peter, one thing you should be careful about is that a cast iron scraping reference will move around on you if it hasn't been religiously stress relieved.

At Rich's class, one of the attendees brought one of Craig Donges' camelbacks, which has not been stress relieved. He rough machined it and scraped it when he got it, but when he blued it up at the Dallas class, it has twisted a couple of tenths. Enough that it would make you sad if you scraped that saddle against it.

Rich told us that you need to stress relieve the casting, then stress relieve it again after rough machining. Stress relief = 1100 F for an hour per inch of thickness.

Richard King
03-17-2013, 10:13 AM
First scroll back to Item 30 where Robert / Lazlo put in the link to Photo bucket pictures we took at the Dallas Class. The second to the last line picture 1 of that line. You will see the part we practice on and it has lines marked on it. That is the angles we like to scrape and flake at 45 deg's. Peter you need to mark your part and practice scraping with out blue to get that cross hatch "checkerboard" pattern.
You also have to stop wet stoning after you scrape a pass. I only use a wet stone when it is off a mile or my last pass cleanup.

You also need to take your surface gage and put it together, lay it on the plate and attach your plunger indicator that reads .0001 or .0005. So you can measure how deep your scraping. To make it easier to see the spots roll some ink directly on your small practice part. You don't show the scraper and it's handle, I do know you need to grind your carbide blade to a 60 mm r or a 40 mm r.
The blade should be ground with a 5 deg neg angle on both sides of it. The blade also looks like you should polish the side of the blade as it looks like it has an uneven side edges. If your scraper is stiff it will make scraping a back breaking chore. If you scroll though the pictures you will see the scraper I use. It is 16" long plus the handle that is another 6" long and I screw on a rubber pad on it so you push the scraper with your body and not pushing it with your arms.

The scraper is flexible and it springs and it's easier to use then the file handle stiff type. When you have your scraper set, then practice pushing the scraper with your hip or resting it in front of your elbow. Push down with about 15 pounds on the scraper so you can remove .0002" material. Try to stop the scraper with a 1/8 to 1/4" stroke. If you have a problem doing that lift the blade up at the end of the forward push and when you get the rhythm of it you will hear a tap tap sound. The divot or low scrape mark should have a opening next to it or high spot the same width of the divot as shown again on Roberts picture. When you perfect that pattern then measure the dept. if it's on average .0002" then slide your finger nail over it and feel the burrs. Then take a dry medium grit Indian sharpening stone and start to deburr the scrape marks. don't press to hard,but stone it lightly until you can not detect a burr.

As Lazlo said be sure to reverse your stance or rotate you vise 90 degs. and scrape it again so you get the checker board look.

Before I scrape a freshly ground or machined part I checker-board the fresh iron to develop the checkerboard pattern and as you scrape the blue spots do not change your pattern. If the part is off a mile then you can increase the stroke length but do not stay in one place to long or you will dig a hole. I tell my students when it is off a mile to scrape it like your scraping off paint. Get it off fast. This is when a round blade helps as if you loose a little control you don't end up scratching the the part with the corner of the blade if it is ground to flat. I'll write more, I'm getting writers cramp.

Peter.
03-17-2013, 01:15 PM
Wow thank you guys for all the advice, I see I have some things to adjust. I've spent a while re-organising my workshop and scraping the rust off a large iron surface plate that I bought to use as a sturdy worktop. Scraping rust seems to blunt the scraper VERY fast :)

My scraper is ground to about a 100mm radius. I will have to adjust this I see. I did have it ground tighter but my scrapes were very thin and stringy, I must have been holding the scraper at too high an angle. I scrape with the handle in the crook of my elbow but my scraper doesn't have much, if any, flex in it. I will look into making a better one with a thinner shank or I might just bite the bullet and buy a commercial one.

I don't use anything like 15lb of weight on the scraper. I will use my dial to check the depth but I think it's shallower than .0002".

I'm off now to put in a few hours practice. I might do a short video later so that you can critique my technique.

Richard King
03-17-2013, 03:06 PM
You can have the scraper higher to pin point scrape smaller spots and lower it to spread or widen the blade contact area. I say those rounder radius's are more forgiving and you unlikely to scratch with the end of the blade. As you begin to "get it" and have better control of the scraper you can grind the blade to a 90 r. Maybe pull out one of the other scrapers and have one with a 90 r and one with a 60 r.

When I was a kid I cut a stiff scraper in 1/2 and added a 3" thinner piece of metal and welded it so I got some spring. No need to buy one I have a plan on making one. I will email it to you as I don't know how photo bucket works and if there is a fee. Rich

lazlo
03-17-2013, 03:10 PM
scraping the rust off a large iron surface plate that I bought to use as a sturdy worktop. Scraping rust seems to blunt the scraper VERY fast :)

If it's that bad, hit it with a wire wheel or a flap disc first. Seriously.

That prismatic scraping reference I posted was right on the money on flatness and parallelism between the bottom and the sloping surface, but when I scraped the top, it as out by ~ 3 thou from the bottom. I facemilled the top, then rescraped it. Scraping that much off, even with a Biax, is a waste of time, IMHO.

Peter.
03-18-2013, 06:33 PM
Here's where I'm at today:

http://peterrimmer.myby.co.uk/images/scraping%20(11).jpg

Measurements are in ten-thousandths. I initially surveyed the flat ways for co-planar with a metric dial and messed up my mental conversion, leaving me thinking that they were .0015" higher one end when it was actually only half that. I scraped the high end heavily a couple of times and ran my digital dial over it and found that it was only a few tenths high so I scraped it again and ended up here. I will bring down that .0004" when I go over the opposite flat ways again.

Here's a closer shot of the scraping.

http://peterrimmer.myby.co.uk/images/scraping%20(12).jpg

I have a ways to go but all in all I'm satisfied with my progress. I found that one of my scrapers is not carbide but HSS and the other is carbide but a huge rigid chunk of a shaft, so I am going to say to heck with it and buy a new clamp-tipped one.

Richard King
03-18-2013, 10:03 PM
It looks so much better, your starting to get the lines going in the right direction to get the cross hatch, almost a checkerboard pattern and with-in .0004" from .0015...good job!! Now start to smooth out the other crappy ways. Remember you scrape the long one first and match fit to the shorter way. You can the scrape the shorter one to "pre-qualify" it to be sure the is not high in the middle or out of parallel before you "match fit" the ways together. Just remember "One way at a time" :-) That's the scraper addiction motto.
Rich

Peter.
03-24-2013, 11:40 AM
No scraping yet this week due to work apart from a little test today but I did manage to score this heavy cast iron pulley off eBay for a fiver:

http://peterrimmer.myby.co.uk/images/diamondlap2.jpg

which soon got transformed into this:

http://peterrimmer.myby.co.uk/images/diamondlap1.jpg

I honed my carbide scraper with the 9 micron paste and all I can say is Holy Cow! The difference in how the scraper now works is amazing. Smooth, controllable strokes with much more material removed and no digging-in. I'm putting a couple of hours in later to see what kind of change it makes to my work.

Erik Brewster
03-24-2013, 12:59 PM
Looking good! From your text descriptions, I thought it was going to look like a beaver scraped it with his teeth, but it is much better than I expected. I think it will look a lot better now that you are honing the cutting edge properly. There were a lot of scratches in the older pictures that looked like a rough scraping edge.

You aren't far out of alignment. A tip on getting a surface into alignment: Take a scrap piece of cast iron and scrape a section flat enough to measure the height accurately (no need for the whole thing). Then scrape, let's say four cycles, on it. Then measure the height again. Divide by four and you will know how much you are removing every scraping cycle. Let's say you take off 1 tenth (0.0001") every cycle, for argument's sake.

Now that you know this, you can scrape a "step" shape into your piece to quickly get it to the correct dimensional size. For the picture you have above, it would work out to 0 scraping cycles on the right. 3 full scraping cycles on the left. 1 extra scraping cycle on the top 1/3 or so of the left. You can even do this without spotting and all, just to "rough it out". Then do a conventional spotting and scraping cycle and you will be very close.

Also, realize that you must scrape consistently for this to work. No scraping hard one cycle and soft to do something else on another cycle.

I know it is addictive to scrape flat and try to just "wing it" to bring it into dimension, but you will be there all day, fighting this one surface. If you "rough it out" with the procedure, it will get finished a lot quicker.

Peter.
03-24-2013, 07:20 PM
Thanks Eric.

I got the surface down flat quite easily with the new scraper I made, but it works so well I over-scraped one edge :(

http://peterrimmer.myby.co.uk/images/scraping%20(13).jpg

Scraper works great - and I found a great source of cheapo scraper tips - used carbide slip gauges off eBay for a couple of quid a pop! I milled a slot in the end of some flat bar and silver soldered the slip into it then cut a tang and bashed on a file handle. Cut the slip to length by notching it with a Chinese diamond cupwheel then whacking off the end, ground the radius then switched to the lapping wheel to put a nice edge on it. Total outlay for the whole setup (not including postages) is 2.50 for the carbide slip, 8 for the cupwheel, 5 for the pulley 10 for the diamond paste and whatever the file handle cost.

lazlo
03-24-2013, 07:47 PM
Wow Peter -- what a transformation! Looking good! :)

Peter.
04-01-2013, 07:07 AM
Peter, one thing you should be careful about is that a cast iron scraping reference will move around on you if it hasn't been religiously stress relieved.

At Rich's class, one of the attendees brought one of Craig Donges' camelbacks, which has not been stress relieved. He rough machined it and scraped it when he got it, but when he blued it up at the Dallas class, it has twisted a couple of tenths. Enough that it would make you sad if you scraped that saddle against it.

Rich told us that you need to stress relieve the casting, then stress relieve it again after rough machining. Stress relief = 1100 F for an hour per inch of thickness.

Lazlo you were right on the money here, I milled the basic shape of a straight edge and found that it has bent like a EU-compliant banana. The only source of heat I have that's even near to 1100F is my gas-fired barbeque with 'fake' coals so I'm going to pile them up, get that good and hot and let the part soak in the coals for an hour or so. Got nothing to lose.

Meanwhile I'm enjoying my new carbide scraper and I've just won a lot of unknown-origin K grade carbide tips for a song so I can make a bunch of different styles and radii scrapers when they arrive.

Just started working on the base, which has a bow and a twist in it so that should be fun. I'm going to machine then scrape a non-bearing surface as a reference first.

Really need to find a dovetail straight edge. Doesn't seem like anyone does them over here new or used.

Peter.
01-29-2014, 01:04 PM
Well a very busy year has passed and that Chinese mill is long gone. I got fed up with falling over the various bits whilst working on my Monarch lathe and sold it off cheap to free up some space.

I recently picked up a Clarkson Mk1 tool and cutter grinder which had a very worn slideway. Using a make-shift dovetail measuring gauge I found that the ways were worn 20 thou narrower one end so I set it up in my mill and machined them parallel with a home-made cutter. Whilst this produced a 10x better fit-up than before and took all the slop out of the table it wasn't perfect by a long shot (the reason for my wanting to learn scraping was because of my poor old milling machine needing work). so I decided to set-about scraping this machine to a better standard of fit. Being a tool & cutter grinder I don't have to worry so much about aligning the ways to each other as on a mill so that takes the pressure off me a little.

So here's the first bluing. It shows up a problem with my milling table and probably made worse by the fact that I had to upset the setup and turn it round as it was just to big to get both dovetail sides on one setup.

http://peterrimmer.myby.co.uk/images/grinderscrape1.jpg

Here's the first pass with the scraper. I scraped it rather heavily after seeing this and went over it twice without bluing, as I knew I had to take a good bit off.

http://peterrimmer.myby.co.uk/images/grinderscrape2.jpg

A few more rounds gets me to here, which I think is looking rather good considering what I started with.

http://peterrimmer.myby.co.uk/images/grinderscrape3.jpg

I'm having trouble getting consistent results with my bluing.

http://peterrimmer.myby.co.uk/images/grinderscrape4.jpg

I realise that it's going on heavy and I try to keep a regular film on my surface plate but it seems that it's very difficult to do. What I do is roll out a small lob of micrometer blue on a 6" surface plate with an ink roller then when it looks a nice and even shade right across I roll out a patch on my bigger plate for bluing the part. After one round of scraping I go over again with the roller and do this 3 or 4 times, but then the part starts getting sucked onto the plate and I have to clean it all off and start over again. My tube of micrometer blue is quite old and almost expired so I'm hoping that fresh stuff will produce better results. Could it be the old spotting blue or is it my technique that's lacking?

J Tiers
01-29-2014, 07:20 PM
To me, the bluing looks about normal for heavy blue.

I don't like the roller approach, I tend to use a lint-free dauber to rub out several spots of blue into a film. Then, I let the film thin out naturally as more and more spottings are done. Usually, it more-or less keeps pace with the surface evening-out.

After a certain point, excess blue just doesn't help. You have to be able to see the "bull's-eye" marks vs the blued areas. The bull's eye marks are a ring of blue around a spot with very thin blue.... indicating a very high spot. You need to see them so you can just hit them, and thus get the surface to "lay down".

If your blue is too thick, the part "floats" on it and never gets to make the bulls-eyes. So you lose that information, and you can't refine the surface effectively.

But at first, thick is good, because it lets you work with bigger problems, higher high areas, and lower low areas.

Try rubbing out the blue on the flat without adding any. The roller may work for you to do that, but I'm not fond of it (at least not now, that could change, I have changed other attitudes).

I roll up a section of lint-free blue shop towel, then poke it into a section of thick wall tube as a handle. You might hate that, or not.

Peter.
01-30-2014, 02:14 PM
Ok thanks Jerry I'll give it a go. I have some new spotting blue on order. The only stuff I seem to be able to find in the UK is Micrometer Blue like I have been using. Perhaps a fresh tube will help.

Another question. How do I choose an appropriate scraper blade radius for the job I'm doing? I use a larger radius at first and smaller radius later as the larger one tends to scrape across to wide an area. Is this right?

kitno455
01-30-2014, 05:15 PM
Mix your existing blue with a bit of WD-40.

allan

Peter.
01-30-2014, 06:00 PM
Mix your existing blue with a bit of WD-40.

allan

Funny you should say that Allan - I had already tried it last year with poor results. Even the tiniest amount thins the blue too much (I squeeze it from a tube, not the tin type).

Tonight I tried Jerry's method of using a lint-free cloth, actually one of those alcohol shop wipes that I had left to dry out. I found that it was quite dry so I tried putting a tiny drop - about 3mm across - of engine oil on my metal bench and squeezed the blue onto it. Mixed it up with the cloth and used it on my plate and instantly I was getting better results.

Today I scored some more stuff for my adventure - a Hilger Watts 12" precision level and an unknown make box level. Got the pair along with the tacho in the background for 50.

http://peterrimmer.myby.co.uk/images/levels.jpg

Peter.
02-01-2014, 05:31 PM
I've put a few hours in today just loads of practice to sharpen my technique. I have a question for you seasoned scrapers - when splitting spots do you always use a single stroke or several small ones on top of each other?

.RC.
02-01-2014, 07:19 PM
I am just a rank amateur, but if that was my piece, at the stage in this photo, I would be splitting up these big sections shown circled in red... If you were to thin out the blue and respot, you would find they are the highest spots... At least that is my way of looking at it...

It would not surprise me if the whole middle is high... If you rock when spotting it is so easy to make a piece convex or high ion the middle, which is the worse case scenerio IMO..http://users.beagle.com.au/lathefan/grinderscrape4.jpg

J Tiers
02-01-2014, 07:45 PM
Another question. How do I choose an appropriate scraper blade radius for the job I'm doing? I use a larger radius at first and smaller radius later as the larger one tends to scrape across to wide an area. Is this right?

I don't, I just use the radius I have. But when I am starting on a piece, I scrape with the scraper way down nearly flat, and longer strokes. As things improve, I raise the handle and rock the blade a little to aim it at smaller spots.

I don't like to dilute the blue.... it seems to make it spot differently, and I don't like it. The dilution makes it spot sort of "blotchy" and not as cleanly as I like. I don't know how to interpret it well.

I also recently started using Canode, which I have kept using. I like the Dykem oil-based High-Spot blue a LOT better, but it is a mess, while the Canode washes off. It is not nearly as good as the oil-based once you get to refining the surface, but it is clean.

In my opinion, any blue that you can see clearly in a photo is way too thick. when I get a surface to a good place, it never seems to show up, the blue is more of a "haze", and can't be seen well in the photo, altjhough it is visible to the eye OK.

The point about rocking the part is very important. let the part's own weight hold it down, and move it from one gripping point, with the same downward pressure on that point at all times. If the part is convex, and you let it rock, it will spot as if it were flat. By holding one end only, you minimize the chance of forcing it flat, or rocking it. And you avoid heating it with your hand.

I was nearly fooled when scraping a straightedge.... I hadn't put on the wood handles yet, but it seemed to be going well, the rotation test was good, spotting was good.

Then I was interrupted. When I got back, I did the rotation test again, and it spun like a top! I cleaned it and cleaned the granite, and all was well. But I was suspicious, because I had not moved the part when I was interrupted.

I waited, and again it spun around. Now I had a clue.... I picked it up , held it a few seconds, and put it down.... perfect! But I kept trying the rotation, and it began to spin again.

The heat from my hand had bowed it and when I scraped it "flat" I really was scraping-in a bow. I put handles on it and went over it again a few times until it was good. Luckily it wasn't much of an error, the heat had not bowed it much, just enough to be detectable.

Peter.
02-01-2014, 08:06 PM
Thanks for the input guys. The middle is high. I spotted it more lightly afterwards and it showed up plain as day. I have stopped scraping this for a while and am working on a small angle-bracket I got, just to get some hours in. I like it because I can do two sides before having to stop and de-burr (no more wet stoning Richard) it, clean it and re-spot plus I can try two different techniques. I found I was working too lightly at first and getting good spots in the middle but hadn't got out to the edges properly so I put some very heavy stripes across it and went again with better results. I'll do some more tomorrow and put up the pics for critique.

dian
02-03-2014, 11:27 AM
carbide slip gages, what a good idea. its weird, but they only come up on co.uk. the selection is somewhat limited at this point in time.

Peter.
02-03-2014, 01:42 PM
carbide slip gages, what a good idea. its weird, but they only come up on co.uk. the selection is somewhat limited at this point in time.

You looking for some carbide tips for brazing Dian? I have a bunch of them all different thicknesses - could send you some in the post.

dian
02-03-2014, 02:01 PM
i would be delighted. what sizes do you have?

Peter.
02-03-2014, 02:17 PM
I got some 18.7mm wide by 3.6mm thick, some 20.3 x 2.3 and some 12.3 x 2.4. Send me your address and I'll pop a handful in the post.

Peter.
02-09-2014, 11:12 AM
I made a significant breakthrough today which has cheered me up and made a huge difference to my scraping. I had made my scrapers by brazing some carbide to some 3/4" x 1/4" cold rolled steel shanks with a file handle on the end. Last night I was watching some videos that Richard King had linked to by Jan Sverre who is a past pupil of Richard's scraping class. I wondered at how easily he was rising dust and how smoothly his scraper was sounding so watched his video a few times over and noticed that his blade was flexing visibly and this got me to thinking that my scraper was a lot more rigid than the one he used. So today I set up on the mill and machined the shank of one of my scrapers down to a taper, from 1/4" to just under 1/8" at the tip, then used my grinder to smooth the edges and put a waist on the shank near the end behind the tip to thin it out some more. The result is astounding, now instead of a 'hard' feel to the scraper which needs careful control of pressure and thrust to avoid digging a furrow or putting fret marks in my scrapes, I have a nice smooth-acting tool that leaves no furrow and my results have improved immediately.

Such a small change with such a huge difference. I'm going to look out for some spring steel now to see if I can improve it further.

dian
02-15-2014, 11:27 AM
finally i found this thread again. so peter sent me carbide tips in three sizes. just great. thanks.

now, whats the radius again, im supposed to grind? (too lazy to search for it.) on a biax it looks like 300 mm or so.

btw, which of jans videos are you talking about? he has so many (short ones).

J Harp
02-15-2014, 09:14 PM
Peter.

Can you post pictures of your modified scraper? My mental picture might not match your scraper.

Thanks.

Peter.
02-16-2014, 04:25 PM
Here's a before and after. The 'after' scraper is a whole heap better to use.

http://peterrimmer.myby.co.uk/images/scraperthin.jpg

J Tiers
02-16-2014, 04:51 PM
Yes, spring, absolutely. Not a lot, but it seems much easier when there is "some" noticeable.

Some might hate it. I like it. TETO.

J Harp
02-16-2014, 10:03 PM
Thanks for the picture. The shaft appears to be narrowed as well as thinned, or is that just an optical effect?

Peter.
06-08-2014, 06:00 AM
Coming along now. I've ditched the file-handle one-piece scrapers and made a new type which uses blades I made for my Biax. I turned a large flat handle from acetal and the difference is huge, now I can get much more even strokes and far better depth control. Got to keep putting the hours in though, this old block must be a fair bit thinner now :D

http://peterrimmer.myby.co.uk/images/scraping (14).jpg

http://peterrimmer.myby.co.uk/images/scraping (15).jpg

I've found that the technique has to be very different for the different grades of iron. The practice block I have here is very soft and gouges VERY easily. It'll even pick up a crumb of iron under the scraper blade and put a fair sized score in the work. I have an old lathe bed I bought for a practice piece which is a bit harder and a small surface plate which is harder yet still. Each needs a different approach, different weight on theblade, slightly different angle. The harder stuff especially I find needs careful angle control or it either slides or digs in.

I went to look at a 24x36 pink surface plate yesterday that was advertised quite cheap but in 'first class condition'. It was a pink coloured plate with flecks of black in it, I don't know the make because the sticker was missing. When I got there I found that it was full of pock-marks where the black flecks had broken the surface. Was quite disappointed for making a 2-hour round trip only to leave without it but I didn't want to waste 100 on something that was no better than the scruffy plate I have now. This can't be a normal thing to happen to a surface plate surely?

dian
06-08-2014, 11:25 AM
whats was wrong with your previous scraper? this one you can sharpen more easyly i guess. how wide is the blade and what and do you leave it at 90? what are you scraping at the moment, except that poor block?

Peter.
06-08-2014, 02:28 PM
I found it hard to control the strokes with the file-handle scrapers and keep them consistent. Pushing with my arms and using hand-grip for power makes my arms ache and control degenerates. I have a physical job so I should be able to handle it as well as anyone else so I decided to change technique after seeing a picture of someone's scraper which had been roughly modded by padding the handle.
I've recently been scraping an old lathe bed I bought for practice, but I thought I'd just scrape the block again yesterday just so I could compare my work to what I was doing earlier. I think it's plain to see that with the practice and the new scraper things are much-improved. Hopefully after the Norway class they will be much better again.
The blades are all 3/4" or 20mm wide, because that is the size of inserts I had.

Peter.
06-08-2014, 06:30 PM
What method do you guys use when scraping the narrow front and rear ways of a flat-bed lathe, in order to keep them perpendicular with the top? So far all I have come up with is to blue them up with a roller and run a square along, observing where it removes the blue and scraping that down. What better method could I use as this is going to wear my square out and introduce errors?

J Tiers
06-08-2014, 08:02 PM
Split up the problem.

1) squareness.... check this with a reference square at the ends....maybe a place in the middle too. Scrape the spots you pick to be square, but don't go down farther than you need to. The reference needs to have some width to it, so you can blue it and spot the way. You better keep that square with the length of the ways also, or it won't blue well

A scraped-flat piece attached to that 4-square you have should work as a direct reference. Sticks down from edge so you set 4-square on bed, and use the added piece to blue the side.

2) flatness..... check this with the "straightedge", bluing and spotting in the normal way. Take some care since it is so narrow.

Scrape everywhere EXCEPT your squared spots.... leave them alone, they maybe won't blue anyhow at first. bring the surface down until the squared spots are blued like everything else. After that try with the reference every so often to keep it square as you get the spots you need..

3) You also need it to be square/aligned with the headstock, but that depends on the reference surface... If referenced on inside edge, some careful measuring can probably keep it square enough. A King-way device would be ideal. if referenced on outside surface it will be OK if the headstock is correct to begin with.

Richard King
06-09-2014, 01:50 AM
You still scraping this one? Peter aren't you coming to the Norway class? I can send you plans to make a BIAX type of hand scraper weather or not, write me and I'll send you the plans...richard@handscraping.com

Peter.
06-09-2014, 02:39 AM
Yea I'm coming to Norway, all paid up just waiting for the day. I'm getting some practice in while I can, just had a free weekend for some DIY chores and time for scraping practice.

Here's the lathe bed I have as a practice piece. I've scraped the top ways and measured the front. Some pretty bad wear here, measurements in tenths of a thou.

http://peterrimmer.myby.co.uk/images/scraping (16).jpg

Jerry - cheers for the tip on using the box square - I should have thought of that myself. I'll make a flat piece to hang off it.

dian
06-09-2014, 03:10 AM
how much is that scraping class?

Richard King
06-09-2014, 10:30 AM
You can contact the Hosts: Norway class I believe is full. Maybe room for one more or a one day class....Have to contact the hosts for the prices. They have it converted to USD and it changes because it was so much for 3 days and extra for the 2 extra days for those who can stay. Rich
Jan has a lot of You-Tube films...he took a 5 day class here in the states about a year ago in Georgia.

> Jan Sverre Haugjord
> Cell phone +4792036935
> Work email: jshaugjord@norsonic.com (if you use this, I will get a copy to jsv-h@frisurf.no)

I believe we have a few openings in the Swedish class. he host is:

Lauritz J. Saxtrup

Saxtrup Arms
(tel) +46 (0)415-15575
(mob) +46 (0)706-408277
lauritz.j.saxtrup@gmail.com

Richard King
06-09-2014, 10:35 AM
Yea I'm coming to Norway, all paid up just waiting for the day. I'm getting some practice in while I can, just had a free weekend for some DIY chores and time for scraping practice.

Here's the lathe bed I have as a practice piece. I've scraped the top ways and measured the front. Some pretty bad wear here, measurements in tenths of a thou.

http://peterrimmer.myby.co.uk/images/scraping (16).jpg

Jerry - cheers for the tip on using the box square - I should have thought of that myself. I'll make a flat piece to hang off it.

Peter your scraping has really improved from those early days. Good Job!