Why scrape when you can grind?

[J.S.H. Products]

In my way of thinking I understand how the scraping works what I don’t understand is how to do long lathe bed without a long straight edge and keep it flat not wavy


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[J.S.H. Products]

I would like to do one of Richard kings classes if he came to Australia because I have some good old heavy machines that could use a little scraping


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[Demon69]

In my way of thinking I understand how the scraping works what I don’t understand is how to do long lathe bed without a long straight edge and keep it flat not wavy


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You can measure a long surface globally in all sorts of ways using indicators-levels-lasers-autocollimators-taut wire etc etc etc. The straight edge is used locally for flatness in overlapping style.

 

[J.S.H. Products]

You can measure a long surface globally in all sorts of ways using indicators-levels-lasers-autocollimators-taut wire etc etc etc. The straight edge is used locally for flatness in overlapping style.

A taut wire that is definitely something I did not consider that could work quite well thanks for sharing your knowledge it is very appreciated


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[Tyrone Shoelaces]

A taut wire that is definitely something I did not consider that could work quite well thanks for sharing your knowledge it is very appreciated


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You would use a taut wire to check out long beds etc in conjunction with an engineers microscope. In the case of a centre lathe you’d put the microscope in the tool post. Zero the wire up at the headstock and tailstock end then you can work your way along the lathe bed, adjusting it in or out as the case maybe.

I had two pin drill chucks fastened to two pot magnets. The chucks would hold the piano wire and you could stick them onto the Chuck face and tailstock face with the magnets. You can tension the wire by winding the tailstock barrel in or out.

Obviously this method only works in one plane. I used a spirit level to get the beds level in the other plane.

Regards Tyrone.

 

[Tex260Z]

Scraping

Scraping is old school and a skill in itself. Old machines had iron way systems that were not hardened. No hardened steel ways like my leblond. No flame hardened ways like my 10EE. Ways like you find on my old Myford ML7. Many old machines off eBay are done! I get one every once in a while knowing I bought a casting kit.

Hardened ways you grind. Old ways you scrape. I am working on an old south bend 9. What can I say I love lathes!!!! it will be scraped and the other parts as appropriate either turcited or brass-ed. Then scraped to fit. I learned brassing from an old machine guy in England. I actually prefer it to turcite. Either way this toy will be tight as a vestal virgin and outlast my days I have left.

My HLV is ground tool steel. Can’t scrape that. My Wadkin PK table saw ways are cool. The sliding table has its own ways on which the bearings run. Wadkin was BAD ASS at green lane works! They attached hardened steel strips with special steel bolts. They break off at a certain torque. Then the whole thing was precision ground. If you shine a glancing light on the ways you can barely see the remains of the bolt circles. Hairline circles. Dead flat!

Hardinge did the same. The T 10 lathe had these type of ways as did the TM/UM mill. These will need to be ground if needed.

Oil pockets are not easy with grinding. The frosted appearance of scraping is just cool.

I have a beat up Oliver shaper. Table needs work from the YawWhos at Boeing. Originally it was ground. I might just send it to nortfield for planning. Planned tops on wood shapers are nice to work with.

So there you go…. Lots of info and no one right answer.

Question for everyone, I have restored the cross slide on my Hercus 9C (reground hardened Ways) with Turcite, my question is do I still need to use Way oil?

 

[Richard King]

Firstly you need to scrape the Turcite - 1. Did you epoxy the Turcite on by setting the saddle on the bed? 2. Or use steel bars clamped on above the saddle? If you used 1. Did you level and align the bed before setting it on the bed? Did you set a heavy weight on the saddle too while it dried?? Did you use overnight epoxy? Tell us. If you mic (mike) Turcite it isn't the same thickness +- .0025 is what they guarantee. So you need to scrape it to fit. When you scrape it the depth of the low to high spot should be .002". The low area is for oil.
I have put Turcite B or (same type, different brands) Rulon 142 on Gleason Curvic Coupling Grinders and did not use oil, but the customer did not want to leave room on the way system a gap for oil. You have a lathe and you need to scrape oil pockets, cut in some oil groves and oil it. It will last longer and not have stick-slip. Do you know how to scrape? Also you will need to make sure the geometry of the saddle is right. Have you planed on this? Make the top cross-slide square to the bottom, so when you face a apart it faces a bit concave.

 

[johansen]

I set my south bend 9 carriage on the turcite strips, epoxy cured etc.

Ran it for a while, it seemed weird. Scraped the middle third down, worked better.. set sand paper against the ways and ran the saddle over it a few times.. worked even better.

Then after that scraped oil grooves in the turcite. (Keep in mind the ways are only half an inch wide) so you need more like a 1/16" burr in a Dremel to grind grooves.. it worked even better still. I prefer a fractal pattern that is random rather than a set pattern.

yes of course you need way oil.

I made no attempt at ensuring the cross slide was perpendicular.

 

[rogertoolmaker]

This kind of corresponds to some of the papers I have read on scraping. They are like "grinding does not actually leave the surface flat" it apparently mounds the metal around into shallow dunes apparently, which seems kind of counter intuitive because you kind of think of grinding as a flattening process, so how is it that it fails to process flatness.

Two "ground" sliding surfaces on a machine way will not hold oil but will squeeze the oil from the surfaces. Whereas a scraped surface has a place for the oil and the two surfaces will slide smooth and easy and extend life of the machine. This is really a necessary operation for a smooth long lasting machine. I have re-scraped the way on surface grinders that would wear out your arm. After scraping the table would move with your little finger.
Roger

 

[Richard King]

For those who are new and you read something that makes no sense you can click on the writers name and press ignore. I just used it. The no sense gibberish is gone, thank God.

 

[Tex260Z]

Firstly you need to scrape the Turcite - 1. Did you epoxy the Turcite on by setting the saddle on the bed? 2. Or use steel bars clamped on above the saddle? If you used 1. Did you level and align the bed before setting it on the bed? Did you set a heavy weight on the saddle too while it dried?? Did you use overnight epoxy? Tell us. If you mic (mike) Turcite it isn't the same thickness +- .0025 is what they guarantee. So you need to scrape it to fit. When you scrape it the depth of the low to high spot should be .002". The low area is for oil.
I have put Turcite B or (same type, different brands) Rulon 142 on Gleason Curvic Coupling Grinders and did not use oil, but the customer did not want to leave room on the way system a gap for oil. You have a lathe and you need to scrape oil pockets, cut in some oil groves and oil it. It will last longer and not have stick-slip. Do you know how to scrape? Also you will need to make sure the geometry of the saddle is right. Have you planed on this? Make the top cross-slide square to the bottom, so when you face a apart it faces a bit concave.

Epoxied the Turcite on by setting the saddle on the bed, 24 hour epoxy, some weights and clamps (very tight).
Don't have tools to align align the bed (lathe is actually on hard rubber castors). Looked good as far as I could tell with what I had to site it.
Pull scraped the Turcite, scraped oil grooves (since) with thin HSS parting tool I used to scrape down the middle of the vee, (I didn't use strips I folded the Turcite into a sharp vee, and then scraped out the centre when it was dry.
Have hand scraped all the other surfaces. Building a new slotted cross slide, converted new cross slide screw and nut to metric, same for compound. Thanks for the confirmation on the way oil.

 

[Cole2534]

Most of the work I put out off the surface grinder has a VERY NICE oil holding pattern. ;-)

Roger that! My vmc leaves a nicer finish than my grinding skills. Haha

 

[Bill D]

I am sure the enclosed engine is on its way to a different shop to get the top of the engine block ground down on a big surface grinder. It might just pay to scrape the top deck flat rather then finding a shop, and paying shipping, that can grind it flat.
Bill D

 

[Richard King]

Epoxied the Turcite on by setting the saddle on the bed, 24 hour epoxy, some weights and clamps (very tight).
Don't have tools to align align the bed (lathe is actually on hard rubber castors). Looked good as far as I could tell with what I had to site it.
Pull scraped the Turcite, scraped oil grooves (since) with thin HSS parting tool I used to scrape down the middle of the vee, (I didn't use strips I folded the Turcite into a sharp vee, and then scraped out the centre when it was dry.
Have hand scraped all the other surfaces. Building a new slotted cross slide, converted new cross slide screw and nut to metric, same for compound. Thanks for the confirmation on the way oil.

That's cleaver folding the Rulon...I'll have to try that next time. Thanks for sharing!. Rich

 

[EPAIII]

I was just thinking along those lines.

First we are told that scraping produces a flatter surface.

And that scraping leaves shallow valleys for the oil. OK, flatter all over but with valleys.

Then that surface grinding produces a flat surface that does not have those valleys. So two ground surfaces can exhibit stiction.

But then again, grinding pushes the metal around creating hills so it is not as flat as scraping.

But wouldn't there be valleys between the hills where oil could collect?

It seems to me that there is some circular reasoning here. What is needed is actual data. You know, stuff with measured numbers. Meaningful numbers, like what percentage of ground surfaces exhibit stiction? And under what circumstances? What oils were used? The same ones or ones optimized for each type of surfaces?

I have seen and measured things that were ground, assumedly surface ground, which were NOT flat. Often off by as much as 5 or 8 tenths or more at distances of 5 or 6 inches. I am sure they were made in a hurry and the best grinding techniques were not used. Also the machines that ground them may have been worn. So I can understand that surface grinding can go wrong. But what about scraping? Surely it too can go wrong.

Oh, and then what about surface plates. Perhaps in the history of precision, cast iron surface plates were made with the three plate method and scraping. But who today has a surface plate that was scraped? Perhaps there are a few around, but I think the vast majority are made with grinding and lapping. The one I have certainly was. And it seems the people who go around correcting and certifying them use laps.

Don't get me wrong, I am not saying anything. I am asking. And I have a real, practical reason for asking. The table of my mill is not flat. I want to improve it. I may have to learn how to scrap. But I wonder if some form of abrasive removal of the high spots could be used. There is no need for oil pockets and I don't care what it looks like. I just want a flatter surface. So tell me why I couldn't use some form of abrasive removal, checking by spotting it with a surface plate, of course.

Most of the work I put out off the surface grinder has a VERY NICE oil holding pattern. ;-)

 

[Tyrone Shoelaces]

That's cleaver folding the Rulon...I'll have to try that next time. Thanks for sharing!. Rich

Good idea, but I suppose a lot depends on the thickness of the Rulon, Turcite etc. We always used 1/8” ( 3mm ).

Regards Tyrone.

 

[Richard King]

Here is a great video on "Why you Scrape"

He has some others too. One about grinding his parallel.

 

[eKretz]

Good idea, but I suppose a lot depends on the thickness of the Rulon, Turcite etc. We always used 1/8” ( 3mm ).

Regards Tyrone.

I have scored and folded thicker turcite before. Works just fine as long as it's scored first.

 

[4GSR]

Epoxied the Turcite on by setting the saddle on the bed, 24 hour epoxy, some weights and clamps (very tight).
Don't have tools to align align the bed (lathe is actually on hard rubber castors). Looked good as far as I could tell with what I had to site it.
Pull scraped the Turcite, scraped oil grooves (since) with thin HSS parting tool I used to scrape down the middle of the vee, (I didn't use strips I folded the Turcite into a sharp vee, and then scraped out the centre when it was dry.
Have hand scraped all the other surfaces. Building a new slotted cross slide, converted new cross slide screw and nut to metric, same for compound. Thanks for the confirmation on the way oil.

Tex260Z,

If your here in the Victoria, Texas area, contact me and I'll be glad to offer any assistance you may need. Looks like you have it under control there.

 

[CalG]

Fun reading back through this topic!
Hats off to all!

I've always wondered about the "just fer purdy" scraping that Bridgeport turret mills show on the knee ways. They really are just "applied" on top of the ground surface.
Good for oil retention I suppose.