Lathe WAYS repair

Rogue_Machinist · Aug 25, 2020

So I noticed that a good majority of the engine lathes at work all seem to have about .007" of taper over 8". I know its not a big deal but many most of them do NOT have DRO's so its hard to "tap into size". Especially our old Okumas which are .002" graduations. Is there a way to redo lathe ways without sending them out?

M.B. Naegle · Aug 25, 2020

Can you see the wear or is it just in how they're cutting? Are you sure they've been leveled properly? Proper leveling has nothing to do with how "level" the bubble is, it's in how true your ways are aligned to the spindle.

eKretz · Aug 25, 2020

Absolutely check the lathes for true (levelling is the easiest way, as M.B. noted). If the problem is wear, it's still quite easy to "tap in" a fairly true diameter - if you don't have good DRO, you don't use the dials to do that, you use a dial indicator set to register on the cross slide or the tool/toolpost, etc.

For an actual repair if necessary, you'd need to either scrape the ways of the bed and under the saddle or get them ground. Generally most guys get the bed ground and scrape the underside of the saddle. That entails adding some turcite to the underneath of the saddle to restore lost height so that leadscrew and etc. are back where they belong.

Before going that route though, make sure that is for sure the issue. Could be as simple as a levelling needed or a little tweak to the headstock angle. And I'm assuming you are measuring this taper with the work held only in the headstock right? If you're using the tailstock it could just be that the tailstock is offset. Not sure of your experience level so if that's already obvious, no offense intended...

michiganbuck · Aug 25, 2020

It can be a bugger running various lathes at work. Chuck can run out or have wobble. Headstock can be off alignment, bed can have a wash out area, tail can be off center or low, saddle can be wore wide, lathe can be not level or twisted, bearings can be shot…and the boss doesn’t care or let you use a day to figure it out, he just wants you to make print. .… I remember running an old OD grinder that had all those things wrong.. it was a bugger.

Working in a shop that had 6 clunker lathes I tried to only use the one that i knew all /most of the bugs.

Having a ground centered round stock can be an asset... 18, 24" or better

Richard King · Aug 25, 2020

Do you have a maintenance manual for the machines? Read the leveling instructions as lathes should be checked at least 1 time a year if they are tool room or production, most Asian Lathes have a headstock alignment pin under it so you can sweak in the head. Do you use the lathes to do shorts only in the chuck or do you use the tail stock. We need some pictures.

Tom Lipton has a show on lathe Leveling. lathe leveling procedure - Bing video

http://vintagemachinery.org/pubs/2104/3558.pdf

Rogue_Machinist · Aug 25, 2020

Thank You for all these answers. Ive been in this trade for almost 20 years professionally. I started in my Uncles Engine shop on a Large Monarch that had only about .001" taper over 10". Granted it was purchased brand new by my uncle and he kept it mint. Barely had paint missing.

But to answer your questions. First the tail stock height has been adjusted to be within .0004" (per "maintenance guy"). They are mostly Okuma and Fortune Engine type lathes. And are in a job shop/prototype shop. They are mostly used for parts less than 4" long. But im finding myself more and more frequently having to run 8" to 24" parts and having to fight the machine to get the taper out. Not to mention my owner is more reactive than proactive when it comes to machine maintenance. They havent been well maintained. But I will watch the leveling procedure and possibly see if that might be the issue.

gbent · Aug 25, 2020

One of the ways they often made Asian machines cheaper than the American machines is the headstock does not set on the ways. The headstock has pusher screws on the back that allow the spindle centerline to be easily moved into parallelism with the ways. The reverse is also true, the spindle centerline can be moved out of parallelism due to crashes or heavy cuts.

Richard King · Aug 26, 2020

I found a manual talking about the pin headstock alignment. Look at page 20 and 21...You can move the head so it compensates for wear up by the headstock . Point the tailstock end of test bar toward the operator and indicate until it reads straight by twisting head over on the pin. then realign the tailstock

https://www.wttool.com/common/manuals/3001-0015_c127.pdf

Peter from Holland · Aug 26, 2020

Align(with a precision level) the lathe first before you mess with the headstock
This workaround with the headstock comes at a price off course You get taper on longer work now which you then need to compensate with the tailstock But every position of the tailstock on the ways needs another offset

Peter

Paolo_MD · Aug 26, 2020

I would also make sure that the chuck is in good shape and properly mounted. if the piece is larger toward the tailstock, it could also mean that the jaws of the chuck are bell-mouthed and the piece is allowed to move away from the tool. Similarly, if the chuck is not properly secured to the spindle (e.g. D-mount pins not properly tightened), it could deflect under the force of the cut.

This can be checked rather easily by mounting a piece of stock, indicating it 6-8" away from the chuck, push the end to one side and measure how much it has moved (the high and low points in one rotation would roughly be twice the taper, if bell-mouthed jaws are the problem, it would be obvious while pushing, but spring back almost completely if the chuck mounting is the problem).

Paolo

ballen · Aug 26, 2020

I agree that it's important to first check that the lathe bed is not twisted, and if the headstock can be rotated, that it's in the correct position.

Regarding bed wear, I want to point out something that is often overlooked. If a lathe ways are only worn in the vertical direction, then this produces very little taper if the cutting tool is close to center, and the diameter of the part is not too small.

Example: you are cutting a 2-inch diameter part (1" radius). Your lathe has 0.010" of vertical wear (a lot!) near the headstock, tapering to 0 vertical wear near the end of the part. The difference in diameter that this introduces, if the tool tip is on center, is 2 x 0.010" x 0.010"/1" = 0.0002" over the length of the part.

Wear on the V in the front/back direction has a much more direct effect. For example 0.010" of wear on the rear of the V will taper the part a hundred times as much, 0.020" in diameter.

Demon69 · Aug 26, 2020

Ive only seen one Okuma manual in the flesh and it was a beast, a quality looking machine. Something like this.

I dont suspect itll be much out of level with a monster 1 piece base like that

. But hopefully the manual will spec checking level off unwearing surfaces.
If youre good that way ride a 10-20 sec level up and down the bed on the carriage, pointing inline and across the ways as a quick and dirty check for horrible bed wear.
If that looks good, chuck a 2"-3" slug and turn equal diameter collars over 6" minimum. You can indicate this from the saddle as you would a test bar. Should be 0-0 too 0-pointing towards the operator a smidge.

According to the Okuma pages the HS is adjustable on the LS, which is encouraging.

Keep it simple an take your time, should have a decent idea of whats going on in about an hour or so.
Let us know how you go

Edit:- Ooo forgot to ask which way is the taper going? Fat furthest from the headstock im guessing.

Peter from Holland · Aug 26, 2020

ballen said:
I agree that it's important to first check that the lathe bed is not twisted, and if the headstock can be rotated, that it's in the correct position.

Regarding bed wear, I want to point out something that is often overlooked. If a lathe ways are only worn in the vertical direction, then this produces very little taper if the cutting tool is close to center, and the diameter of the part is not too small.

Example: you are cutting a 2-inch diameter part (1" radius). Your lathe has 0.010" of vertical wear (a lot!) near the headstock, tapering to 0 vertical wear near the end of the part. The difference in diameter that this introduces, if the tool tip is on center, is 2 x 0.010" x 0.010"/1" = 0.0002" over the length of the part.

Wear on the V in the front/back direction has a much more direct effect. For example 0.010" of wear on the rear of the V will taper the part a hundred times as much, 0.020" in diameter.

Wear is most of the time not even on both the front and the back ways That makes the cutting tool go to or away from the centre causing taper And taper is dubble the distance on a lathe You could even scrape the ways to make it not rock So the cutting tool only goes down or up on the centreline That will cause little change in diam on any big parts The smaller diam the bigger the issue then though But it is hard to turn longer on small diameter

Peter

Rogue_Machinist · Aug 26, 2020

Demon73 said:
Ive only seen one Okuma manual in the flesh and it was a beast, a quality looking machine. Something like this.

I dont suspect itll be much out of level with a monster 1 piece base like that . But hopefully the manual will spec checking level off unwearing surfaces.
If youre good that way ride a 10-20 sec level up and down the bed on the carriage, pointing inline and across the ways as a quick and dirty check for horrible bed wear.
If that looks good, chuck a 2"-3" slug and turn equal diameter collars over 6" minimum. You can indicate this from the saddle as you would a test bar. Should be 0-0 too 0-pointing towards the operator a smidge.

According to the Okuma pages the HS is adjustable on the LS, which is encouraging.

Keep it simple an take your time, should have a decent idea of whats going on in about an hour or so.
Let us know how you go

Edit:- Ooo forgot to ask which way is the taper going? Fat furthest from the headstock im guessing.

That Okuma is almost what ours looks like. Ours is gray though.
And I do love use it. 6 jaw adjustable chuck. And great power.

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