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Lathe: Cross slide not parallel with bed

Projectitis

Plastic
Joined
Aug 12, 2022
Hi everyone,

I purchased a (new) hobby lathe/mill combo a year or so back, and decided to tram/align it before using it.
I want to align the mill to the cross slide, but the first thing I noticed is that the cross slide is not parallel to the bed!
The headstock end of the cross slide is lower than the tailstock end (see photo). Luckily, the difference is uniform along the length of the cross slide (it is not warped or twisted).

The difference is about 0.07mm over 90mm travel (2-3 thou over about 3.5").
  1. Is this enough to worry about?
  2. If so, how do I go about levelling the cross slide? What do I look for - where do I start?
Thank you!
Peter
 

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EPAIII

Diamond
Joined
Nov 23, 2003
Location
Beaumont, TX, USA
For the most part, the error you show will not have any bad effects on the use of a lathe. A tool post is attached at one place on the cross slide and left there for one operation or even for many. Some users may not move the tool post for years.

What is important is that the cross slide's travel is very close to perpendicular to the main ways. And any small error is in favor of a facing cut producing a concave face instead of a convex one.

Unless you discover some operation where this causes a real problem, I would just ignore it.
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
A.003 tilt that way should not have a noticeable effect, except for having a parting tool tilted perhaps .001. Still should not be any problem..

You might check to see if the saddle is down on the bed with no chips under it..same for the cross slide. just eyeball and perhaps feel with a feeler.
Most likely they made it a little off.
 
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Projectitis

Plastic
Joined
Aug 12, 2022
Thanks for the quick responses. Sorry, I should have added some more info:
This is a lathe/mill combo, so the cross slide is also the mounting surface for the vice (and workpiece). The cross slide travels along the bed to provide the x-axis travel for the mill.
So for lathe work I can see it wouldn't be a big deal, but for milling it might be.

I generally work on pieces up to 200mm in length (but usually shorter). This could result in a difference of 0.15mm (6 thou) across the workpiece (8").

I guess the easiest is to shim the vice and not worry about the cross slide?
 

Projectitis

Plastic
Joined
Aug 12, 2022
Thanks for the discussion, people.

I mounted the vice with a 0.05mm (2 thou) shim under one edge without adjusting the cross slide. Some more checking with needle gauge and careful tapping with a mallet before tightening the bolts, and there is now no needle movement in any direction.

Beautiful. More than happy with that!
 

EPAIII

Diamond
Joined
Nov 23, 2003
Location
Beaumont, TX, USA
So now you tell us it is a combo machine.

I had a similar situation with my Unimat. The cross slide was off by over 0.015" and that is on a smaller machine. I had problems when milling with the table they sell for that purpose. Sure enough, when I checked the top of the cross slide was off in both X and Y directions. I found that very disappointing after reading all their claims for accuracy.

"Trust but verify!" Well, no, "Distrust, verify, and correct!"

I set up for milling and used the largest diameter milling cutter I had to trim the top of the cross slide down to parallel. My milling problems went away. Well, at least that one did.



Thanks for the quick responses. Sorry, I should have added some more info:
This is a lathe/mill combo, so the cross slide is also the mounting surface for the vice (and workpiece). The cross slide travels along the bed to provide the x-axis travel for the mill.
So for lathe work I can see it wouldn't be a big deal, but for milling it might be.

I generally work on pieces up to 200mm in length (but usually shorter). This could result in a difference of 0.15mm (6 thou) across the workpiece (8").

I guess the easiest is to shim the vice and not worry about the cross slide?
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
shim the vice is OK.

I often come in with and top touch (feel) a shim with a parked tool on a one-up part to be sure a part will be in spec. often quicker than indicating. I don't trust a vise for just clamping a close size. A run of parts you are just stuck with an average of the vise accuracy.
 
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implmex

Titanium
Joined
Jun 23, 2002
Location
Vancouver BC Canada
Hi Projectitis:
Now that you have solved your immediate problem, do you intend a more permanent fix at some future date?
Obviously it would be ideal to have the top of the table level, and of course, the way to do that is to scrape it in.

The decision whether to make the considerable effort depends on whether you're otherwise satisfied with the machine.
These combo machines have severe shortcomings even when they are well made (a rarity).
You will get very tired of having to forever convert them from one mode to another, and if they are crappily made on top of that, you will become frustrated trying to do anything but the crudest sort of work on them.

So my inclination is to recommend that you upgrade as soon as you can, and buy standalone machines...a lathe for turning and a mill for milling.
What you buy depends on your budget and how lucky you are with what comes across your field of view, and how much machine you can support...size, weight, power requirements etc etc.

Buy good quality, and if you don't yet know what that looks like, engage a buddy who knows the turf to advise you.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 

Terry Keeley

Stainless
Joined
Oct 18, 2005
Location
Toronto, Canada eh!
Tighten the gib up so it's fairly snug, if that doesn't help I'd think you'd havta shim the low side up.

Please tell us it wasn't you that painted that machine fuchsia?
 

neanderthal mach

Hot Rolled
Joined
Dec 18, 2008
Location
princeton b.c.
Yeah that fushia color. (cough, cough retch) but it's part of the corporate colors for the Optimum brand of machines sold I think mostly in Europe. Just a paint color and placard re-brander like Grizzly and many others. But with enough semi subtle sales BS trying to imply "German Engineers" have or had something to do with the design so they can tag it with a higher price. Leaving aside it's status as a banned machine here since the real question was how to fix or work around what he has. The OP should start with this. https://pearl-hifi.com/06_Lit_Archi...s/Schlesinger_Georg/Testing_Machine_Tools.pdf Then be well prepared to go through the whole machine using that PDF for the test checks. Without question it will have a few/lot more issues than just the cross slide being out of square to the milling head.
 

Terry Keeley

Stainless
Joined
Oct 18, 2005
Location
Toronto, Canada eh!
I just threw up in my mouth a little...

DSC_0002.jpg
 

Richard King

Diamond
Joined
Jul 12, 2005
Location
Cottage Grove, MN 55016
For the most part, the error you show will not have any bad effects on the use of a lathe. A tool post is attached at one place on the cross slide and left there for one operation or even for many. Some users may not move the tool post for years.

What is important is that the cross slide's travel is very close to perpendicular to the main ways. And any small error is in favor of a facing cut producing a concave face instead of a convex one.

Unless you discover some operation where this causes a real problem, I would just ignore it.
I would start by using a feeler gage to check for gaps between the ways .001 or .0015 . Then move the cross slide off the saddle and Mike (Micrometer) the cross-slide ways front and back. If that is OK then move the cross-slide far enough back and set a .750" gage block on the headstock and tailstock side of the saddle top and crank the saddle forward and back moving the gage block. It should tell you what side is off. The saddle or the cross-slide. The real issue you might have is if you drill holes from the compound off your tool holder. Check it out and lets discuss it. My student Stefan Gottswinter has a good set of videos. He had a good teacher. Lets find out where the problem is before we decide to scrape it.

 
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