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Tony
02-10-2012, 04:35 PM
So for the heck of it I thought I'd take my camera along for the ride...

this is work in progress so no finished shots.

some may remember me asking about cannabalizing an old CI surface plate
to make some tooling.. well, after looking for a CI blank big enough, and
trying to beg/borrow/steal/buy a camelback with no luck, the surface
plate looked ever more appealing.

I hope you guys enjoy playing along and if I could get any comments,
criticisms, pointers, tips, tricks it'd be greatly appreciated!

My first real attempt at video editing, too. Originally started talking /
voice-over but 'thats not what I sound like!' and when some local HSMers
(italian) got wind of what I was doing they wanted to see it too (suckers! :) )
I thought I'd take the Muellernick approach and subtitle it (as its easier
to change languages)

enjoy:
http://youtu.be/LkdkouWiDFs

Tony

(ps for anyone who's even thinking marble, I tried that (despite the voice
of reason on the forum) -- its readily accessible and I got a dozen or
so "cut offs" about the right size (24"x2") -- free!

ALL of them had a dip somewhere in the polished surface. The best one was
5/6 thou low on center) .. I thought if I checked enough of them I'd find one
that was passable.

duckman
02-10-2012, 05:12 PM
First you need to stop clamping the straight edge in a vise, every time you do it puts stress in it, rig up a spot on your bench that will hold it, like a cradle, with the cradle you just place it in it and it holds itself, that way you can turn it end for end and scrape the other way. I've been scraping for way to long and have never seen bluing rolled on we always used a dauber, put the bluing on the dauber and rub it around until its as thin as you want.

lazlo
02-10-2012, 05:29 PM
I use a vise to hold the workpiece. As long as you don't crank down on it...

http://i164.photobucket.com/albums/u15/rtgeorge_album/Scraping%20Class/IMG_4224.jpg

gcude
02-10-2012, 05:43 PM
Looks like you are trying to grind down the surface with your stone. Need to just let the weight of the stone do the work of reducing the burrs your scraper has raised. Just use your finger tips to lightly glide the stone over the surface. From the light scratches left by your scraper, looks like you need to change the angle on the tip or increase the radius of the tip. Looks like you are well on your way to getting there. Great job so far. Not exactly a right way, but maybe you can continue to pick up bits and pieces to make the job go quicker. Thanks for posting your progress. I'm sure others will benefit from your efforts.

Tony
02-11-2012, 04:41 AM
There are rubber soft jaws in the vise; I figured it safe.
Perhaps as I get closer to the final surface I'll knock together
a wooden jig to sit it in.

Forrest Addy
02-11-2012, 09:41 AM
Hold the work any way you want while you scrape it so long as the grip puts no permanent deformatins in the work and so long as no heat is introduced. Remove all gripping force when applyng the work to the reference tool for taking a "print". The wrok when printed should be completely free of restraint and in thermal e3qualibrium.

Here's my riff about applying blue to a surface plate from my scraping class lecture notes:

A dauber is fine for spreading blue. It's been around for centuries adapted from the printer's trade. Remember that an ink roller is maybe 4 times a quick at spreading a uniform film by actual time trials and the applied film has fewer cntaminants. Printer's use rollers now except in working museum displays.

Also the very act of vigorpously rubbing out a thin film not only generates friction heat but some transfer and contract media pigments are mildly abrasive. The rubbing wears the reference tooling. Have you noticed that the Canode yellow gets duller the more you rub it out? The duller color comes from the dark gray cast iron wear particles mixing with the brilliant yellow Canode pigment muting its intensity.

A roller almost eliminates friction heat and wear from application. A roller is quicker and more efficient. I don't say this to make anyone feel unhappy or shat upon. This is not an assertion but a fact based determined from time trials agaist a stopwatch. When it comes to spreading a thick sticky paint pigment in thin films a rubber breyer (roller) is many times quicker. Secondarily, there is practically no abrasion because there is so little rubbng contact between roller and work.

Don't take my word for it. Time yourself with a stop watch rubbing out a film of blue with a dauber on a sirface plate. Then clean the plate and roll the same amount of blue with a 3" long SpeedBall soft rubber breyer from an art supply house. It should take 15 to 25 seconds per square foot for the roller.

Hint: lift and let the roller spin freely in the air for a second at every reversal. That way you never run the same part of the roller over the same part of the plate.

Film thickness:

You want enough pigment on the plate to make it vividly colored but the color should be transparent - you should see the texture of the plate clearly through the film. I've determined the film should be 0.000030" to 0.000060"" thick.

The question is how much pigment paste is that? Do the math. A12" x 18" plate has a surface area of 216 sq in. 216 square inches x 0.000050" film (average thick) = 0.010 cubic inches. Assume a 1/8" dia pigment "nurdle" ("nurdle" is the technical term for a glob of paste product issued from a tube). 1/8" dia = 0.012 square inches. 0.011in^3 /0.012in^2 = 0.80" long nurdle. Break it up into 6 to 8 dabs about 1/8 dia x 1/8 long. YMMV. This is a guide to roughly quantify how much blue to apply to a surface plate and not an exact formula. Pull back the tube slow as you squeeze and the nurdle will be larger in dia than if you moved the tube quicker.

Anyway about 6 to 8 dabs 1/8 dia x 1/8 long per square ft is close enough for a first approximation for a intial application of pigment to a surface plate or other reerence tool. Use about half that for re-application when the blue gets thin.

This formula isrough - intended to give you a place to start. You will have to adapt it to suit your style and equipment. Don't think you can get away busting my chops about picky details. I have a reciprocal deal with the bitchy women of the world: hassle me on this formula and there will be someone loud, shrill, and intensly annoying to nag you EVERY time you leave the toilet seat up, leave the cap off the toothpaste, or fail to pick up your dirty clothes.

lynnl
02-11-2012, 12:25 PM
Well I don't know diddly about scrapeing. But I did enjoy watching that, and I do appreciate Tony taking the time to produce and post it.

I especially appreciate NOT having to listen to some annoying music while I watched.

But as an ignorant bystander, I had the following thoughts:
1. It seems he's taking much broader scrapes than necessary, that are also removing metal where it's already low, i.e. non-blued areas.

2. That's much finer (shallower) scrapes and much more random than I typically see on the "frosted" surfaces of commercially produced mill and lathe ways. Are those commercially frosted marks purely for looks and/or oil retention? Or are they also essential for flattening purposes?

I make those comments, not as critiques of Tony's work, but in hopes someone will correct/inform me.

Mcgyver
02-11-2012, 12:56 PM
I especially appreciate NOT having to listen to some annoying music while I watched.
.

amen, why do people feel the need to impose some unrelated and crappy piece of music on their audiences. stupid people...take away their right to vote I say :)



It seems he's taking much broader scapes than necessary, that are also removing metal where it's already low, i.e. non-blued areas.


until you get bearing points all over the surface, you scrape in regions...ie if only the right and left sides of a piece have bearing points, you're not trying to scrape the high spots of the left and right sides....you're trying to scrape all of the left and right sides...I'll put a pic at the end that might make it clearer



Are those commercially frosted marks purely for looks .....

yes imo; oil retention is imo a flawed concept.

http://i785.photobucket.com/albums/yy132/michael01000/scraping/Photo0008.jpg

lazlo
02-11-2012, 01:23 PM
yes imo; oil retention is imo a flawed concept.

Frosting, I agree, but every scraping book (Connelly, Michael Morgan, ...) recommended flaking for oil retention, as does Rich King.

Rich told us the story that his Dad (the inventor of the Kingway alignment tool :) ), did an experiment where he rebuilt two identical machines. He flaked one, left the other hand scraped. The machines were professionally operated and maintained, but ways on the non flaked machine wore considerably faster.

J Tiers
02-11-2012, 01:45 PM
Holding in a vise is fine... although your vise that moves around so much would make me crazy....... vise and table should be connected to the planet in a solid way.

However, LOSE those hand-holds in the straightedge.

Get some pieces of wood, and bolt them on through the handholds.

Otherwise, every time you pick up the work, you will heat and expand the "backbone", and the bottom reference surface will arch upwards, leaving a hollow in the middle.

You won't really see this, what you WILL see is that you never can get it quite right, and the more you try, the worse it gets.

So today, before you knock off work, spot the thing. Draw a picture of the blue, or better, take a digital photo, and then clean off the straightedge. Let it be overnight.

Then go down tomorrow, blue the flat, and pick up the straightedge with thick gloves on, or a thick rag over each part you touch.

Spot it right away, and see. If the middle is now the high place, OR IF THE PATTERN IS IN ANY SIGNIFICANT WAY DIFFERENT FROM YOUR PICTURE..... THEN you know that it was probably getting bowed or distorted as you held it while spotting.



but ways on the non flaked machine wore considerably faster.

Possibly those low spots just gave a place for grit to go and not be between the surfaces..... then a wipe every so often removed it.

I think flaking looks frankly idiotic, personally.... frosting is a much better finish visually.

Plus every ebay idiot flakes the ways, maybe with a grinder. It has become an "overused cliche".

ironnut
02-11-2012, 02:01 PM
I too don't know diddly about scraping and Tony's video was most illuminating. I like Tony's scraping tool. Is there a complete photo of it or a similar design available? I am thinking I would like to copy it. I have a seasoned casting of a small Camel back and I want to scrape it as a reference tool. I bought Connelly's Book and the series on scraping in Home Shop Machinist has been great. I am still trying to work up the courage to have at it.

Thanks again Tony and to the others for their comments and suggestions.

gordon

Tony
02-11-2012, 02:34 PM
thanks all for taking the time to watch / comment.

JT the vise is rock solid / bolted down tight what you're seeing
is the flex in the soft jaws. I think I got them from mcmaster some
kind of urethane maybe 1/4" both side so even though you see
me snug the vise pretty hard i get a lot of squish and the straightedge
can move left/right (just not up/down).

So far, personally, I like the pull style scrapers (ironnut check youtube
for "grattage suisse" you'll see some more images of the scraper.. thats
basically where I copied them from)

but the pull scrapers cut a wider swath.. that insert is maybe 1/2" wide
compared to the cut the anderson makes.. maybe 3/16"? due to the
radius. still not sure what the "end effect" is .. we'll see.

and yes I'm trying to get the surface down so the entire straight edge
prints so the spotting now is just an indication of where to really
haul off material.

once i get it all to spot i'll switch to the thinner blade and see how
good of a surface I can get.

I'll be sure to post pics as I get on with the work.

I'll also install some wooden handles, thanks.

Tony

Mcgyver
02-11-2012, 03:05 PM
Frosting, I agree, but every scraping book (Connelly, Michael Morgan, ...) recommended flaking for oil retention, as does Rich King.

Rich told us the story that his Dad (the inventor of the Kingway alignment tool :) ), did an experiment where he rebuilt two identical machines. He flaked one, left the other hand scraped. The machines were professionally operated and maintained, but ways on the non flaked machine wore considerably faster.

that a mechanic wrote it down, and I'll call them mechanics because that's the context verses engineers or scientists, does not make it so. Its plausible that beliefs were based on correlation not causality. Besides there has no doubt been bearing and tribology learning since Connelly's great work. I don't know Rich's anecdote, but it is just that; too many variables to draw a conclusion from.

Everything I've found on hydrodynamic bearing design from an engineering vantage point conflicts with the notion of oil retention pockets. If the surfaces are are separated by the wedge of oil, having low spots is undesirable; it increase chance of high spots making content. If the bearings are NOT separated by the wedge and contact occurs between the high spots, then there is rapid wear. how did the pockets help again? The oil is suppose to magically lift itself out and form a wedge that separates the high spots? whats left behind, a vacuum?

I've been trying to get with a Prof on the subject to find better understand if I'm missing something or whether oil retention is the crock I suspect it might be...hasn't happened...but I seek reasons and science not just that its the way its always been..because the 'how its always been' seems conflicted with the engineering I've read on it

lynnl
02-11-2012, 03:12 PM
...until you get bearing points all over the surface, you scrape in regions...ie if only the right and left sides of a piece have bearing points, you're not trying to scrape the high spots of the left and right sides....you're trying to scrape all of the left and right sides...I'll put a pic at the end that might make it clearer


OK, that makes sense.
Thanks

lazlo
02-11-2012, 05:12 PM
Besides there has no doubt been bearing and tribology learning since Connelly's great work. I don't know Rich's anecdote, but it is just that; too many variables to draw a conclusion from.

It's certainly possible that Whitworth, Connelly, Michael Morgan, Rich King Sr. and Jr., and all the major machine tool builders (who carefully manufacture the bed ways with flaking) are wrong, but I doubt it :)


Everything I've found on hydrodynamic bearing design from an engineering vantage point conflicts with the notion of oil retention pockets. If the surfaces are are separated by the wedge of oil, having low spots is undesirable

Non sequitur. The purpose of scraping deeply (i.e., avoiding "Chickenscratches" that most noob scrapers do) is to provide oil reservoirs. Two perfectly flat surfaces wring the oil out between them.

The flaking crescents add substantially larger oil reservoirs.

I think some people may be dubious of flaking because they've spent a lot of time learning to scrape, and they don't want to learn another skill. Flaking freehand is *hard*. Then again, I came across a Biax half-moon power flaker for a song, so I've been unmotivated to pick up the skill.

lazlo
02-11-2012, 05:21 PM
Good article from the Moglice guys about scraping versus flaking.

http://www.moglice.com/articles/straight_talk/straighttalk.html


Why scrape? Plain bearings do offer important advantages over rolling elements and so scraping lives on. The scraping procedure attempts to spread the points of bearing contact evenly across the whole bearing face, while achieving the correct geometric alignments. In fitting a way, workers identify points of contact by applying thin coats of marking compounds to both surfaces. After sliding the surfaces against each other for about an inch, the technician removes the slide and examines the bearing points left in the marking compound.

A common standard is ten to fifteen points in any one square inch of bearing area. It is possible, and to a certain extent desirable, to achieve forty or more points with repeated fine scrapings. Whether the count reaches ten points per inch or forty, the percentage of area in contact should be 50 to 60 percent. The spaces between high and low points provide oil reservoirs important to accuracy and long life. When bearing contact exceeds 80 percent there is an effect similar to the ringing together of joe-blocks resulting in "stick-slip" effects.

Thousands of high and low spots in a scraped surface provide evenly distributed oil reservoirs, and drains. As motion starts, oil is dragged between high spots across the whole surface. Perfectly flat surfaces ( 100 % ) at rest would with time squeeze out all oil and ring together. As this “sticktion” is overcome, the slide must move the distance between oil grooves to become lubricated. At that point, the slide rides up on a hydroplane of oil without the draining effects of the low spots in the scraped surface (like the thread of a tire), the slide rises up several thousandths causing inaccuracies.

Breaking up a bearing surface with a power spotter, which leaves a series of half moon shaped marks on the ways, provides a quick fix for this problem. These spot or flaking marks are not to be confused with scraping. Developed as a cosmetic treatment, the marks give the surface a uniform appearance. Today, spotting provides relief in bearing surfaces that have lapped themselves flat by wearing through their relief. Spotting will not improve the straightness or flatness of a way surface, but it will help with stick-slip problems.

michigan doug
02-11-2012, 08:24 PM
Informative. Thanks for sharing. I like watching while somebody else walks their way up the learning curve. I might miss one or two of the pot holes.

Finest regards,

troy

J Tiers
02-11-2012, 08:49 PM
Ah.... I think lazlo's post provides a "tie breaker" opinion



Breaking up a bearing surface with a power spotter, which leaves a series of half moon shaped marks on the ways, provides a quick fix for this problem. These spot or flaking marks are not to be confused with scraping. Developed as a cosmetic treatment, the marks give the surface a uniform appearance. Today, spotting provides relief in bearing surfaces that have lapped themselves flat by wearing through their relief. Spotting will not improve the straightness or flatness of a way surface, but it will help with stick-slip problems.

gcude
02-11-2012, 09:52 PM
Rich King also thinks everyone is flaking many surfaces possibly to the detriment of their machine. Although he whole heartedly supports flaking select way surfaces, he also says the oil pockets are fine places for grit and fine swarf to collect and actually aid in the premature wear and grinding down of your machine surfaces. More food for the debate. ;)

dp
02-12-2012, 12:53 AM
There's some other considerations, too. For oil to move from one low spot to another there has to be an adjacent low spot to migrate to. On a wetted surface that may not be possible as all low spots are already filled. In that case hydroplaning happens. That would be the case for pretty much any properly oiled bearing surface, in fact. There's another issue and that is wave front. When pushing a fluid ahead it will resist to the degree the surfaces demand and that will create a bow wave which is a lifting force. This creates a series of pressure waves as one surface glides past another. To witness this, oil your ways and cinch up your gibs a bit. Now slooowly feed in. It works. Now quickly feed in - should bind some. That's the bow wave and trailing waves at work.

This is a well known dynamic of fluids and is what causes ripples in sand on beaches, and sand dunes, or in more extreme cases as when glacial lakes burst their ice dams, you get mega-ripples like we have in Washington State:
http://www.ndsu.nodak.edu/pubweb/~sainieid/columbia-plateau/

RussZHC
02-12-2012, 12:57 AM
Thanks Tony...getting tempted to attempt this myself :eek: (though I can be, shall we say, not the most patient of people)

Oh, if anyone wants, a bit of a close up of the tools which Tony had previously post in that thread
http://bbs.homeshopmachinist.net/showthread.php?t=39202&page=158

vpt
02-12-2012, 09:47 AM
That looks like allot of work.

J Tiers
02-12-2012, 11:50 AM
That looks like allot of work.

It is.

But that was how most all machines were made 80 years ago. It's easier when you have powered scraping equipment, and factory templates, etc. And when the parts are supplied machined to a very close-to-final shape so you can pretty much do the same stuff every time, without surprises.

There were powered scrapers in the 1920s, they just looked a lot different from a Biax..

J Tiers
02-12-2012, 12:06 PM
If you REALLY want to know what Rich King says, instead of what someone else "says that he says"...... check here. There is a post BY Rich king in which he clears up this issue. Post #15

http://www.practicalmachinist.com/vb/general/connellys-spotter-froster-p-172-a-240860/

lazlo
02-12-2012, 12:13 PM
That looks like allot of work.

It is. That's why you should beg, borrow or steal a Biax if you're planning on doing any substantial amount of scraping.

In Rich King's class, he has you scrape-in a gage block by hand, to get the basics down, and realize how tedious it is. Then he switches you over to a power scraper, which is at least 5 times faster, and much less fatiguing.

You'll never go back :)

Tony
02-12-2012, 02:39 PM
That looks like allot of work.

I think I've lost 5 pounds already .. or 60, if you count the surface
plate :D


I've gotten the surface down to about 6 or maybe 8 spots per inch and
have switched to a smaller scraper (thinner blade).. and now its getting
very hard to see the spots. The blue is very light and the surface now
is much shinier than it was.

Can i ask someone to shed some light on using a contrast pigment?
i assume I just pick some yellow paint from art supply and put it on the
straight edge before spotting? any trick to keep it from turning into a big
green mess?

Tony

lazlo
02-12-2012, 02:45 PM
If you REALLY want to know what Rich King says, instead of what someone else "says that he says"...... check here. There is a post BY Rich king in which he clears up this issue. Post #15

http://www.practicalmachinist.com/vb/general/connellys-spotter-froster-p-172-a-240860/

LOL! Yes, Jerry -- thanks for that post on Practical Machinist, where Rich writes exactly what I just posted. No surprise since that's what Rich taught us (including GCude) in our class :rolleyes:



1/2 moon flaking is an extra deep oil pocket. Hand Scraping depth averages .0002" and 1/2 moon flaking averages .002" deep.

The majority of machine builders scrape their last pass on a scraped surface a bit deeper or 1/2 moon flake.

I have always taught that you 1/2 moon flake the unexposed surface. I believe if you flake the exposed surface your pockets will capture dirt that will not be squeegee out with a way wiper. I once talked to a Bridgeport Engineer at The IMTS Chicago show when I was demonstrating the BIAX 1/2 moon power Flaker in the DAPRA booth. I told him they flake the wrong side because it looks so nice/ He said "if they change the way wipers once a year, there will not be a problem" I have rebuilt hundreds of Bridgeport's and the majority wipers were original and were never changed..so much for that !!

There is always the debate about 1/2 moon extra deep flaking. I find it helps extent the life of the ways as it holds pocket of oil under the ways all the time. One must be careful where you use it. Flake the unexposed surface. It's not as pretty, but it lasts longer. As said earlier you have to have to have oil pockets so you do not get stick slip. Not [deeply] scraping [on the last pass] or oil flaking a way is like ringing gage blocks together. They stick!!"

lazlo
02-12-2012, 02:54 PM
By the way, people keep bugging me to re-post my thread from PM about Rich King's scraping/machine alignment class in Arlington:

I've been reluctant to do it, because these kind of threads here often turn into silly pissing contests :rolleyes:

Rich King's scraping/machine rebuilding class (Picture Heavy)
http://www.practicalmachinist.com/vb/general/rich-kings-scraping-machine-rebuilding-class-picture-heavy-230333/


Can i ask someone to shed some light on using a contrast pigment?
i assume I just pick some yellow paint from art supply and put it on the straight edge before spotting?

You roll-on a very, very thin coat of contrasting spotting compound before you spot it on the surface plate. In my picture above, I've contrasted with yellow canode, and then spotted with blue.
To completely honest, I'm not a big fan of the contrasting colors. It looks cool, but if you have good light, you really don't have problem seeing the high spots.

J Tiers
02-12-2012, 04:44 PM
LOL! Yes, Jerry -- thanks for that post on Practical Machinist, where Rich writes exactly what I just posted. No surprise since that's what Rich taught us (including GCude) in our class :rolleyes:

Well, lets try that AGAIN with the RIGHT part made bold.

Changes the meaning just a bit, doesn't it......?



I have always taught that you 1/2 moon flake the unexposed surface. I believe if you flake the exposed surface your pockets will capture dirt that will not be squeegee out with a way wiper. I once talked to a Bridgeport Engineer at The IMTS Chicago show when I was demonstrating the BIAX 1/2 moon power Flaker in the DAPRA booth. I told him they flake the wrong side because it looks so nice/ He said "if they change the way wipers once a year, there will not be a problem" I have rebuilt hundreds of Bridgeport's and the majority wipers were original and were never changed..so much for that !!

The picture in the Connelly book is a device Anderson once made. I have one in my collection and it works as described by some of the other guys. I also show my method of 1/2 moon flaking in my DVD,

There is always the debate about 1/2 moon extra deep flaking. I find it helps extent the life of the ways as it holds pocket of oil under the ways all the time. One must be careful where you use it. Flake the unexposed surface. It's not as pretty, but it lasts longer. As said earlier you have to have to have oil pockets so you do not get stick slip. Not scraping or oil flaking a way is like ringing gage blocks together. They stick!!

In other words, if you want to flake something, do the UNDERSIDE of the carriage, NOT the ways.........

lazlo
02-12-2012, 05:08 PM
In other words, if you want to flake something, do the UNDERSIDE of the carriage, NOT the ways.........

I was replying to McGyver's comment that flaking serves no purpose. My response was that the crescents provide oil reservoirs, which I noted that Rich King taught us improves the wear resistance of way surfaces. It wasn't hearsay, I didn't read it in a book, as you can see from the pictures I posted on Practical Machinist...

Rich also told us to flake on the underside of the ways, as his post indicates. That's a very clever optimization of oil flaking, which avoids getting crud in the half moons. On my Hardinge HLV, the bedway is ground, and there's beautiful checkerboard flaking on the underside of the saddle, and the underside of the topslide.

J Tiers
02-12-2012, 05:27 PM
On my Hardinge HLV, the bedway is ground, and there's beautiful checkerboard flaking on the underside of the saddle, and the underside of the topslide.

Flaking? Or "frosting"?

I've always understood the "nike swoops" as "flaking" and the checkerboard (Brown and Sharpe) scraping as "frosting".

The "frosting" is not typically as deep as the big "gouges" of "flaking", it is more a pattern style of finish scraping.

Elsewhere R.K. makes the distinction, giving the "flaking" a depth of 0.002"......

TGTool
02-12-2012, 06:41 PM
<snip>
On my Hardinge HLV, the bedway is ground, and there's beautiful checkerboard flaking on the underside of the saddle, and the underside of the topslide.

Robert, do you have any pictures of that? I worked with a little German grinder years ago that had beautiful work that sounds like your Hardinge.

It would be nice to have a small collections of photos of particularly nice scraping and flaking or frosting work. Pictures of Moore's scraping or someone else who capitalizes on the little crescent scrape marks would be nice.

TexasTurnado
02-12-2012, 06:47 PM
I was replying to McGyver's comment that flaking serves no purpose. My response was that the crescents provide oil reservoirs, which I noted that Rich King taught us improves the wear resistance of way surfaces. It wasn't hearsay, I didn't read it in a book, as you can see from the pictures I posted on Practical Machinist...

Rich also told us to flake on the underside of the ways, as his post indicates. That's a very clever optimization of oil flaking, which avoids getting crud in the half moons. On my Hardinge HLV, the bedway is ground, and there's beautiful checkerboard flaking on the underside of the saddle, and the underside of the topslide.

So what did Richard prefer when the underside is Turcite instead of ci? Did he recommend flaking there? I have not seen that recommended with Turcite but I have lived a sheltered life...:D

I plan to mill oil passages in the Turcite with a ball em mill as I did on the Colchester, but am wondering if anything else is required.

lazlo
02-12-2012, 07:51 PM
Robert, do you have any pictures of that? I worked with a little German grinder years ago that had beautiful work that sounds like your Hardinge.

I don't but I'd be glad to take some Jan.

lazlo
02-12-2012, 07:55 PM
So what did Richard prefer when the underside is Turcite instead of ci? Did he recommend flaking there? I have not seen that recommended with Turcite but I have lived a sheltered life...:D

Yes, we flaked the Turcite for the same reason -- I have pictures in the PM thread. I think I mentioned via email that I tried to power flake the Turcite (just to see what it would do) after Rich told us to hand flake it , and the Biax made a mess like he said, even on the shortest stroke at the lowest speed :)

TexasTurnado
02-12-2012, 08:17 PM
Yes, we flaked the Turcite for the same reason -- I have pictures in the PM thread. I think I mentioned via email that I tried to power flake the Turcite (just to see what it would do) after Rich told us to hand flake it , and the Biax made a mess like he said, even on the shortest stroke at the lowest speed :)

Interesting... did you happen to take any pictures of that?

Mcgyver
02-12-2012, 10:38 PM
I was replying to McGyver's comment that flaking serves no purpose. My response was that the crescents provide oil reservoirs, which I noted that Rich King taught us .

I found response a bit frustrating because in essence says 'its the way everyone says to do it so it must be so' rather than explore the my reasons (right or wrong) for questioning flaking. A long with a list of mechanics and commercial firms (who might very well do so for marketing reasons and momentum as for any other) and 200 year old inventors. Hmmm. No disrespect to Rich or anyone else on the list, but how does he know? He's got PhD in bearing design? My mechanic does a great job with my car but I'm not about to accept as gospel his views on thermodynamics and exhaust gas turbulence.

Listing more mechanics who say 'do this' without explaining the science or engineering of these oil reservoirs are supposed to work isn't is a counter point - I know the idea conflicts with the popular view held by machine tool dealers. How sure are you that they say that because they deeply know the tribolgy of hydrodynamic bearings? Or maybe it was because they were told to when apprentices or perhaps notice a correlation and took it as causality. Lengthening the list of those who think oil reservoir work doesn't support or undermine the science though. If they right, there needs to be some science that explains why the bearing engineer with a PhD is wrong

The conflicts I see with the popular mechanics view of flaking (and i said all this already but it was ignored) are:

1) if there is not metal to metal contact, the pieces are correctly riding on a wedge of oil. Pockets do not help anything

2) if there is metal to metal contact at the high point, rapid wear will occur where this happened, and the pockets failed to stop it

3) high point not hitting high point depends on the geometry of the wedge. The wedge then is determined by the viscosity and ANY variance in the distance between the parts will upset the geometry of the wedge and increase the likelihood of high points colliding which = rapid wear

4) Finally, if these 'reservoirs are supposed to be our bearings saviour, how is that suppose to work? the oil magically rises and leaves behind a perfect vacuum? The oil isn't going to come out of the reservoir because there is nothing to replace it. metal to metal contact will occur, rapid wear results.

There may be very good reasons I'm missing and that I'm wrong, but because Whitworth, Connelly, Michael Morgan, Rich King Sr. and Jr., and all the major machine tool builders (somehow you've surveyed this) says 'well that's the way its done' neither makes it so or answers the above points. These people are experts at mechanics; getting things aligned, parallel flat etc. I do not see how that at all qualifies them as experts on the science of what is going on inside a hydrodynamic bearing. Whats got me questioning the merits of flaking is the conflict between what machine tool builders say and what PhD's specializing in bearing design/tribology say.

J Tiers
02-13-2012, 12:42 AM
....................No disrespect to Rich or anyone else on the list, but how does he know? He's got PhD in bearing design? My mechanic does a great job with my car but I'm not about to accept as gospel his views on thermodynamics and exhaust gas turbulence.
.................................
Lengthening the list of those who think oil reservoir work doesn't support or undermine the science though. If they right, there needs to be some science that explains why the bearing engineer with a PhD is wrong

The conflicts I see with the popular mechanics view of flaking (and i said all this already but it was ignored) are:

1) if there is not metal to metal contact, the pieces are correctly riding on a wedge of oil. Pockets do not help anything




Well,

1) The guys DOING THE WORK of reconditioning are quite likely the ones who WILL know what works...... They've seen that "stuff done this way works", and also "stuff done that way does not".

They may not know WHY, but they know "WHAT". The PHDs can study and explain it later.

2) I've found that PHDs are NOT always the best sources of info. I happen not to be one, but I have them in the family, and elsewhere....

A PHD does NOT mean you know everything. What it DOES mean is that you are "certified" as able to FIND OUT things in a systematic and acceptable way, and to have the background understanding of your subject area to do that without gross errors. There is a big difference.

AND, there is no reason at all why a person with NO PHD cannot find out the very same things...... they may even have an understanding of the subject equal to that of a PHD. They lack the "academic qualification" which academic purists can cavil about (and seemingly love to).

3) the "wedge" lubrication requires a certain combination of geometry, clearance, viscosity, surface finish, and relative speed of movement to develop. I am by no means certain that a real "wedge" develops in a slow moving slideway..... I am pretty darn sure that it does NOT, in fact.

An advance of 3" per minute is so slow that I have a great deal of trouble associating it with wedge buildup in the way that a rotating bearing has the effect. The geometry is bad for it anyway.....

It is entirely possible, I think, that the true explanation has more to do with the 3D shape of the "pocket" produced by the "flaking". If anything the multiplicity of 'edges" and the sloping shape of the recess may serve to collect and re-distribute oil.

Quite possibly the flow in them is even contributing to "micro-wedges" as oil is turbulently "wiped" out of the recesses when more oil moves past them due to movement of the slide.

if you put oil between smooth surfaces, and rub them, the oil is rubbed-out, appearing at the edges. I don't know that the oil is retained better over the whole surface by pockets, but they WILL be harder to "empty" than two smooth surfaces without pockets. The experiment is fairly easy to perform.

The very slow movement puts a premium on having oil available, since there WILL be metal-to-metal contact after a longish time of no movement. You can either wait for oil to be wiped underneath, OR you can provide some "in situ'..... the latter seems better to me.

But if you "flake" an open area where chips can fall, that seems like a stupid idea leading to the collection of way-grinding swarf and grit there. It's no different than any other "gouge" in the surface, aside from scale.

Mcgyver
02-13-2012, 09:08 AM
1) They may not know WHY, but they know "WHAT". The PHDs can study and explain it later.
.

but when they are saying different things, it should draw the attention of the inquisitive mind.



A PHD does NOT mean you know everything. What it DOES mean is that you are "certified" as able to FIND OUT things in a systematic and acceptable way, and to have the background understanding of your subject area to do that without gross errors. There is a big difference.
.

it means more than that, but no argument from me, kind of stating the obvious, that it doesn't mean the know everything. However i'm not randomly selecting PhD's, I'm reading books on bearing designs by specialists in the field.


3) the "wedge" lubrication requires a certain combination of geometry, clearance, viscosity, surface finish, and relative speed of movement to develop. I am by no means certain that a real "wedge" develops in a slow moving slideway..... I am pretty darn sure that it does NOT, in fact.

There you are in disagreement with the bearing engineers. How did you become so sure?


An advance of 3" per minute is so slow that I have a great deal of trouble associating it with wedge buildup in the way that a rotating bearing has the effect. The geometry is bad for it anyway.....

I'm an not extrapolating hydrodynamic theory from rotating bearings, it was presented for linear as well in machine tools


It is entirely possible, I think, that the true explanation has more to do with the 3D shape of the "pocket" produced by the "flaking". If anything the multiplicity of 'edges" and the sloping shape of the recess may serve to collect and re-distribute oil.

Quite possibly the flow in them is even contributing to "micro-wedges" as oil is turbulently "wiped" out of the recesses when more oil moves past them due to movement of the slide.

interesting.


if you put oil between smooth surfaces, and rub them, the oil is rubbed-out, appearing at the edges. I don't know that the oil is retained better over the whole surface by pockets, but they WILL be harder to "empty" than two smooth surfaces without pockets. The experiment is fairly easy to perform.

In a hydrodynamic bearing there has to be a supply of oil. if the oil is rubbed out, as per my point 4, with the high points touching (most of the surface if ground) if the oil is supposed to come out of the pockets and form a wedge what is left in the void?

TGTool
02-13-2012, 09:53 AM
In a hydrodynamic bearing there has to be a supply of oil. if the oil is rubbed out, as per my point 4, with the high points touching (most of the surface if ground) if the oil is supposed to come out of the pockets and form a wedge what is left in the void?

I'm no PhD either, but my visual hypothesis is that with the flaked surfaces there's no net change in oil volume. Oil that's drawn from one space is replenished by adjacent passages between small oil reservoirs. Same for oversupply that can escape through small passageways. Oil is drawn into the close contact surfaces as the two parts move and is continually redistributed.

I'm standing on the side of "experience has shown that ...", by the way if it isn't obvious. The flaked way theory of bearing longevity still makes sense to me.

lazlo
02-13-2012, 09:56 AM
Interesting... did you happen to take any pictures of that?

I'll call you John.

Mcgyver
02-13-2012, 10:02 AM
I'm standing on the side of "experience has shown that ...", by the way if it isn't obvious. The flaked way theory of bearing longevity still makes sense to me.

Certainly there is that; and I probably never would have questioned it had I not read on the subject. I think I'll try and contact the author of the bearing book and ask if he can contribute or shed light on this specific area.

My frustration isn't that "I'm right everyone is wrong", far from it....its a notion out of step with tradition and if I'm wrong no big deal. The frustration is in not being able to rationalize or understand what seem conflicting views on how its supposed to work.

On the subject of experience has shown, how universal is this? Other than bridgeports I'm trying to think of machines I've had apart so you could see if the hidden mate had flaking: Dean Smith & Grace, Standard Modern, XLO, Monarch...don't recall flaking there, but perhaps it was worn away

lazlo
02-13-2012, 10:14 AM
Other than bridgeports I'm trying to think of machines I've had apart so you could see if the hidden mate had flaking: Dean Smith & Grace, Standard Modern, XLO, Monarch...don't recall flaking there, but perhaps it was worn away

The XLO and Monarch's have flaking. At least my XLO does, and I've seen the flaking on 10EE's.

Tony
02-13-2012, 01:28 PM
One thing I'm not quite sure of (among many) .. as I start getting
up there in points per inch (using a smaller scraper), should I be
using yet an even smaller scraper (cutting edge / radius / etc), or
the same scraper and, using less pressure, try to just meticulously hit
the spots I'm trying to take down?

Tony aka "run-on sentences"

Wirecutter
02-13-2012, 02:17 PM
A PHD does NOT mean you know everything. What it DOES mean is that you are "certified" as able to FIND OUT things in a systematic and acceptable way, and to have the background understanding of your subject area to do that without gross errors. There is a big difference.

AND, there is no reason at all why a person with NO PHD cannot find out the very same things...... they may even have an understanding of the subject equal to that of a PHD. They lack the "academic qualification" which academic purists can cavil about (and seemingly love to).


Thank you, thank you, and thank you again.

No, I am not a PhD. I work in a company with about 500 employees, 6 of which are PhDs. All six are in the same department I work in. All these people (5 men, one woman) are very good at their jobs. None claim to know everything, and none are the stereotypical Absentminded Professor. They have in-depth specialized knowledge of certain topics, and are paid for the use of their brains. It's not often that I need to "Ask a Doctor," but when I do, it's pretty cool that there are several only steps away.

What I like about these people is that, like many on this forum, they can be a resource to me when I need to know about certain things, or how best to find out. (Sometimes 'smart' really can rub off.)

-M

- edit - And of course, I don't ask my physician about metal working, nor do I ask my coworker about how deal with a medical condition.

J Tiers
02-13-2012, 10:16 PM
There you are in disagreement with the bearing engineers. How did you become so sure?


the rotating bearing has "a" wedge (when the speed etc are correct) which is in part caused by the geometry of the setup, the difference in radius and the ability of one part to move. The circular space has no end or beginning, so the wedge location is related to external forces.

below a certain relative speed of motion, the wedge is no longer built up, it flows away as fast as it is supplied, and metal-to-metal contact is possible.

The sliding bearing has a different setup altogether.... there may be a series of what might be called "turbulence wedges", with the front one likely depending on what the 'leading edge" of the shorter piece is like.... and succeeding ones depending on minute non-flat areas.

the function of a "flake pocket" may be to encourage the formation of "turbulence wedges". The sloping "lead-in" or "lead out" may have a function as well.

But the speed is so small, well below the relative speed at which the rotating bearing probably has no wedge action, that the concept of the "wedge" likely needs either a far more viscous lubricating material, or one must consider a different mechanism altogether. the gross first level mechanism may be simpler.

Oil serves to provide a shearable medium between the two microscopically rough surfaces, tending to prevent the roughnesses from interlocking to cause severe friction.

if the bearing area is simply pumped-full of oil from within the bearing surface area, there obviously will be a film to do the job. there is no need to consider "wedges", the space is full of ample oil under pressure to hold the parts apart.

If there is no pressure pump, but the leading edge of the sliding part is sloped or shaped to guide "ambient" oil to the area between the surfaces, that is similar to pumped oil, but may likely have some 'wedging" action, as the geometry is strikingly similar to the rotating case.

if the oil is intermittently pumped-in, but no pressure is held, then the oil is in a continual process of being squeezed and rubbed out (or left behind), but is replenished (hopefully) before the surfaces actually meet.

If the two are simply rubbed with no oil added, eventually the film will be reduced in thickness until the rough surfaces begin to interlock and wear each other, as various areas become "dry".

The action of the "flake pockets" may simply be to collect and re-distribute the remaining oil, based on their somewhat random pattern (the lines of "swoops" are rarely perfect, and often overlap when sighted along the way) That would tend to preserve the maximum amount of oil across the surfaces, rather than allowing some areas to run dry early. In turn, that would certainly be likely to minimize wear in an adverse situation.

The wedge seems less than relevant to the slow moving case, except in the one instance of the "lead-in slope", which guides oil between the surfaces from an external source.

With oil supplied from underneath, or already present underneath, the "wedge" is un-needed to explain the action.





In a hydrodynamic bearing there has to be a supply of oil. if the oil is rubbed out, as per my point 4, with the high points touching (most of the surface if ground) if the oil is supposed to come out of the pockets and form a wedge what is left in the void?

Your first error may be to view it as similar to a rotating bearing, despite your protests to the contrary.

Your second error is probably to take the "reservoir" idea too literally.... think of it as a collector and re-distributor.

Tony
02-14-2012, 09:37 AM
hey guys, my apologies for the OT :D but I thought I'd post some pictures.
Its impossible to get a good shot of these things. In person its almost
iridescent.. in some spots I can start to see reflections of my tool as I
work past them.

Getting close(er):

http://img.photobucket.com/albums/0903/knucklehead/scrape/DSCN0731.jpg

http://img.photobucket.com/albums/0903/knucklehead/scrape/DSCN0729.jpg

tried taking some photos of the spotting but it comes up so light its
hard to see let alone photograph.

I have some deep scratches here and there.. would happen sometimes
if (when using a lot of pressure) the tool would roll on me and a corner
would dig in.

Not sure if its worth scraping down past them as
1. that would suck
2. it'd probably happen again
3. saves me the trouble of making "oil resevoirs" ha.

made a smaller scraper which makes the shorter strokes easier:
http://img.photobucket.com/albums/0903/knucklehead/scrape/smallscraper.jpg

Tony

lazlo
02-14-2012, 10:14 AM
It's looking good Tony, but it looks like you need a more radius on your scraper tip -- you're scaping too broad, and too shallow (Chickenscratches).

Rich showed us a trick to measure if you're chickenscratching: run a tenths DTI across the clean, scraped surface. The difference between the high and low spots should be 2 - 4 tenths.

Tony
02-14-2012, 10:27 AM
and if I were to tell you my scraper has no radius?
would you be mad at me?

But I think you might be onto something here.. ie see my previous question
in this thread (smaller tool?) which would be equivalent to a radius on the
tip.

answered my own question, i did?

thanks for that number, by the way. time to take some measurements.

Tony

Don't get me wrong I can move some serious (by my standard) metal with
this scraper (inset) -- like literally plow a trench in one pull. What I cannot
do is get more "resolution"

which I suppose I could with a radiused tip.

gcude
02-14-2012, 10:49 AM
In regards to radius, Forrest Addy suggested a rough rule of thumb was coffee can, soup can, fruit juice can. He gives more precise measures than that, but this will get you going in the right direction.

TGTool
02-14-2012, 10:55 AM
Robert,

I've been watching that quality as well and musing on it. This may be a deeper subject than first appears. Mike Morgan talks about "hard" and "soft" bearing.


Mike Morgan
Hard or point bearing has steeper deeper relief <graphic here in text>

Hard bearing, sometimes called point bearing, is a bearing surface made up of discrete points with a defined space between each point.

The quality standard (qs) is normally expressed in points per inch for this type of bearing. The size and number of points per inch, along with their spacing, are the main criteria for determining the "quality" of the bearing. Point bearing is the most common type of way bearing surface applied to machine tool ways. This type of bearing is used when a way surface will be in direct bearing contact with another sliding or fixed machine element. The individual points distributed evenly throughout the way surface provide for an even distribution of pressure throughout the contact area. The space between the points provide space for the distribution and storage of lubricant. In a "picked" surface the space between each point of bearing is far below the actual bearing surface.

Surface or soft bearing has very gradual shallow relief <nother graphic>

Surface bearing (sometimes called "shallow" or "soft" bearing) is a bearing surface made as close to a perfectly flat plain as possible, with almost no space between one point and the next.

For this reason the qs of this type of bearing is normally expressed in terms of percentage of contact. This type of bearing surface is used only for special applications, as it provides for no distribution of lubrication. Friction from direct contact of two surfaces of this type is dramatically increased. This is caused by the increase in surface to surface contact. One application of this type is found in special gauge surfaces that cannot use point type bearing. Another application is as race surfaces of part of a rolling element bearing set.

This type of way is sometimes used in special machines such as Ex-cello thread grinders. This type of surface provides the absolute maximum contact area with another surface and is very difficult to achieve. It is only used when maximum contact area is required.

The Swiss pull scraping, particularly with the flat cutting face, may be a philosophical choice to produce what Morgan calls a soft bearing, and further, that the Swiss (or that opinion group) believes way surfaces should be close to perfectly flat. Morgan and King are clearly in the different camp with the oil distribution pockets and reduced contacting surfaces. So Mcgyver and perhaps his mentor may be descendents of that line of thinking. And further (speculating wildly here) it's possible that with small machines and mechanisms in the watchmaking manufacturing their experience with small ways may actually lead to different conclusions about what is the best bearing surface.

Tony
02-14-2012, 01:15 PM
TGT interesting quote/thought. That poses a bit of a problem for me.. if
I'm using the "Swiss" method.. how do I tell when I'm done? ie I have no
points per inch. At least "ideally" I wouldn't. I suppose just a dial indictor
would do that trick -- but much more of a pain than watching spot density.

I wonder if I'm 'learning' the wrong technique.

Tony

TGTool
02-14-2012, 01:44 PM
Tony,

With a flatter surface as you're developing, you would worry less about points per inch. Of course that will still show you if your have holes or areas that don't mark up, but if you have reasonable contact all over, then just do the same technique of setting off some arbitrary inch square areas and estimate what percentage is blued. Morgan doesn't comment on a target percentage, but Rich King says 40 to 60 percent contact is ideal. You can still look at your target areas and count points which would be some measure of uniformity over a smaller area. I'm not sure what the right answer is. I think Morgan feels that even for surface plates and straightedges it should be a hard bearing - that is, that there should be deeper depressions between contact points but some of this may really be a matter of preference.

lazlo
02-14-2012, 07:44 PM
and if I were to tell you my scraper has no radius?
would you be mad at me?.

That's why you're not getting any "resolution" - you're plowing the surface.

The ideal is that you mark the high spots, and scrape them off. As you get finer and finer, you need an increasingly smaller radius on the tip. That gage block I scraped above is over 50 points per inch, and the final scraping tip I used was the size of your pinky and roughly a quarter's radius.

lazlo
02-14-2012, 07:51 PM
The Swiss pull scraping, particularly with the flat cutting face, may be a philosophical choice to produce what Morgan calls a soft bearing, and further, that the Swiss (or that opinion group) believes way surfaces should be close to perfectly flat.

Swiss pull scraping scrapes deeply, just like Richard Moore, Whitworth, Rich King, et al do. If you look at a Dixie or SIP, it has the same beautiful, scintillating reflectance that you get from deep, overlapping scraping marks:

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


The pull scrapers have a small flat blade that looks like a screwdriver, and it looks like they rock it up on the edge to spot:

http://www.youtube.com/v/TFCVO0fXW1k


With a flatter surface as you're developing, you would worry less about points per inch.

The "soft bearing" isn't any flatter -- it just has less surface area to hold oil. In other words, the soft bearing is asymptotically like a ground surface, which has no oil pockets at all, and therefore maximum stiction.

Doesn't the Excello thread grinder have pressurized oil ways like the Harig surface grinders?

TGTool
02-14-2012, 08:16 PM
Yes, I was drawing somewhat from that video and one of the things I noticed is that when he's sharpening his scraper there's no hint of establishing a radius. He draws it flat across the stone. He does have a smaller one for fine finishing though which would be the equivalent of smaller, precision spotting. Still, closer to index finger size than pinky.

.RC.
02-14-2012, 08:16 PM
We had a play with a pull scraper at the Melbourne scraping class... I was amazed at how deep it scrapes... As did some with it, then went over the top with the Biax.... It took several Biax cycles to remove the pull scraping marks..

lazlo
02-14-2012, 08:28 PM
Yes, I was drawing somewhat from that video and one of the things I noticed is that when he's sharpening his scraper there's no hint of establishing a radius. He draws it flat across the stone.

Yes, they're definitely flat -- they look a lot like a screwdriver to me. But as you can see from that Dixie picture I posted, they can get damn fine on the scraping PPI. That's why I'm guessing they're rocking up on the edge. I just shot an email to Rich asking about it...

This is a picture from a Swiss PM member, showing a close-up of the Swiss pull scraper. I remember Evan bought a bunch of them that looked the same, with some additional ones with a distinct trapezoid shape that I presume is for getting into the corners of dovetails:

http://www.practicalmachinist.com/vb/general/hand-scraping-dixi-jig-mills-186035/
http://i13.photobucket.com/albums/a290/stefi1/DSCN0033Large.jpg
http://i13.photobucket.com/albums/a290/stefi1/DSCN0035Large.jpg

TexasTurnado
02-14-2012, 09:12 PM
The pull scraper I use for Turcite is very much like the Swiss scrapers in the video: it is sharpened essentially flat. I'm sure it has some radius as I have not made any real effort to make it exactly flat:

http://i288.photobucket.com/albums/ll168/TexasTurnado/P8250071.jpg

I sharpened it flat to prevent digging in and try to keep it razor sharp, as this makes it easier to control how much is taken off with each stroke. When it gets dull, it tends not to cut, and then suddenly cuts deeper than intended.

When sharp, it takes almost no force to scrape and take off a consistent depth of cut. Even without making a conscious effort to use the corners, it is possible to make points much closer together than the width of the blade, as the photo above shows. This photo was taken before milling in the oil channels with a ball em (as shown on the prismatic way at the top).

J Tiers
02-14-2012, 10:31 PM
The video is good, I have seen it before....

BUT, it's horrible practice to have the work so close to and *above* the reference flat..... You WILL get grit on the flat..... he happily brushes off the grit, seemingly TOWARD the flat which is only a about 500mm away.

Please to move farther away!

But you can get a very nice finish pattern with the pull scraper..... I have seen the suggestion to very slightly round the corners.... no radius to the edge, just the corner. That seems to be a good suggestion, it works for me.

if you were to radius a pull scraper edge, you would be gouging the surface deeply due to the convexity.

Tony
02-15-2012, 09:36 AM
yes knock the sharp corners off .. two swipes with a diamond file / card
does the trick -- didn't take me long to learn that one.

but I'm writing to say that something magical happened today.

magical and a little sad.

my passes are getting finer and finer. The last round I did sitting on a
stool and really getting my aim down. anyway, hit the surface with a rag
and grabbed the stone to debur before checking my progress on the plate.

put the stone down and just as I started moving well didn't that stone
take off like a rocket straight across the straightedge, hit the floor and
break in two? first time it felt like that.. like an air hockey puck.

long story short set it up on the surface plate, divided it into 4 equal
sections along its length and ran a tenths indicator along each line.

0.0003-0.0004" across 24".
the deepest "scrape" i could find was 0.0005 but I had to do some hunting
around (it was near an edge).

(note my surface plate claims to be good to 0.00012)

I have to admit I'm a bid giddy and I apologize maybe this is old hat
to everyone but for someone who's only screwed around with the
odd angle plate or two getting something that flat with a caveman tool
just blows my mind. Sure, I know, that was the point right, scrape it
because its the only way to get it flat .. but still.

I couldn't get it that flat on my mill
(granted my mill doesn't have a lot going for it).

I've since wrapped the handle in a few turns of heavy cord for
thermal isolation and I'll be knocking together a jig to hold it
from here on out. I'll be sure to post pictures.

Tony

Tony
02-18-2012, 12:47 PM
for anyone who might be interested / following along, here's the
2nd (and final) part .. also shorter than the first:

http://youtu.be/jx1D0buRCOY

-Tony

J Tiers
02-18-2012, 03:15 PM
Good that you have the hand-holds with insulation.

But watch out when you carry and hold for spotting.... when you get to the small errors, the cumulative errors from heating the metal can get significant....

I had one piece do that... you could not really notice the error, but if you did the "spin test", it would not pivot in the correct places (2/3 to 3/4 along opposite to end you push/pull). Everyting was much better after the wood handle went on it