View Full Version : squaring a lathe

10-24-2001, 06:40 PM
Okay, I have a 19" sumit lathe with an 80" bed. It is in excellent shape and well cared for. Here's my problem, my bed is square and level, but no matter what I get .001" taper per 4" when boring a hole, always bigger towards the chuck. How do I make sure the lathe spindle is square and true with the ways.


10-24-2001, 07:57 PM
A tapered hole when boring is more likely to be caused by the bending of the boring bar rather than the lathe being out of alignment. See if a regular outside turning exhibits the same behavior before trying to adjust a not-out-of-adjustment machine.

10-24-2001, 08:00 PM
Boring or turning it doesn't matter

C. Tate
10-24-2001, 08:44 PM
Where do people usually do most of their work? Close to the chuck. The ways may be worn more there. You can use your leveling screws to twist the bed and remove a one thou taper. Are you absolutely sure the machine is level? To be level you must use precision levels perpindicular to each other and check the entire length of the bed and adjust accordingly. It is possible to use the cut and screw method. Take a cut, check the taper, set an indicator and screw the leveling screws the direction you need to remove the taper. This is crude and may not produce satisfactory results over the length of the lathe. If your floor is not heavy enough the weight of an 80 inch lathe can cause you concrete to "give" a little over time this can also cause your problem.

Good Luck

10-24-2001, 10:42 PM
The headstock is bolted to the bed, isn't it? Look for those bolts and one or more jack screws to swivel the head. Adjust the head, several times probably, until the taper you get is adequately small. (Seems to me it's not so bad now, but certainly some work requires more accuracy, maybe .0005 over 6") Obviously test cuts should be light, and on a large diameter test piece to minimize workpiece deflection.

10-25-2001, 09:19 AM
Take a look at http://people.ne.mediaone.net/wasser/NEMES/RDMLatheAlignment.html

It's THE way to do it. Use the technique to check alignment up near the headstock as well as farther out. If you can get the lathe aligned at some distance from the headstock but not up close, that's a good indication the lathe bed is worn by the headstock. If you can't get the lathe aligned by shimming the feet, no matter what or where, you may need to shim the headstock where it sits on the bed, but that's pretty unlikely if it was a good lathe to begin with.

10-25-2001, 12:26 PM
These here newfandangled machines, they don't know how to buid one anymore, the headstock is supposed to bolt to the ways, and them there chunks that bolt in the ways called a gap, never take them out if you can keep from it.

So first, is this a gap bed machine, might be a problem with a burr or chip under gap section.

Also, most of these newer machines have an adjustable headstock, 4 bolts, large dowel at front, adjuster at rear. On a Clausing you have to tear down feed gear train to get to this adjuster. Couple of set screws acting on blocks, a push me arrangement.

Easiest method for me is to chuck up a good sized bar in the good chuck, I use the 4 jaw, take a cut with a good tool. measure it out and use a tenth indicator mounted on carriage and do calculations and corrections. Saves setting up gears and taking second cut, then tearing down again for more adjusting, then another cut. Tenth indicator much faster.

Look at the back of the headstock for this adjuster, do you have the book on this machine, information on this adjuster should be in it.

Good luck.

10-25-2001, 08:21 PM
Thanks I think I can handle it from here!

C. Tate
10-25-2001, 11:19 PM

Would like to know how you fix this problem if you don't mind.

10-26-2001, 10:26 PM
Checkout SGW's wed site, it did the trick.
Sometimes I try to make things to complicated! It's way to simple, no paper shims tho. I have adjustable machine levelers.

10-26-2001, 10:27 PM

I also would like to hear your solution.