View Full Version : Is this bad??

02-20-2005, 01:53 PM
I set up my lathe last nite and tried to level it. My first time ever.

On a 3 inch cut I had a taper of .001 Is this really far off or am I close?



02-20-2005, 02:25 PM
"It all depends on what you're doing...."

Personally, I think I'd find that amount of taper unacceptable. It's not terrible, though. You are close. Now that you're close, tweak the lathe mounting a bit, try another cut, and keep adjusting until it's cutting parallel. It won't take much.

02-20-2005, 02:36 PM
But, how do we know that any error is a result of the lathe being out of level, or having a very slight twist in the bed?
I guess that'd be a reasonable assumption if the ways are brand new out of the factory...

02-20-2005, 02:38 PM
Well the lathe isn't new. Matter of fact, it's about 36 years old. I will tweak it slightly and see what happens.

02-20-2005, 02:48 PM
<font face="Verdana, Arial" size="2">Originally posted by Ryobiguy:
But, how do we know that any error is a result of the lathe being out of level, or having a very slight twist in the bed?
I guess that'd be a reasonable assumption if the ways are brand new out of the factory...</font>

The purpose of leveling the lathe is to remove any twists in the bed.

02-20-2005, 02:51 PM

could you describe your set up for the cut?..


02-20-2005, 03:42 PM
You do not state the dia. of the stock your cutting or if it's between centers. If the stock it light could be defection from tool force. Even a little crud on the jaws could cause this much taper.


02-20-2005, 05:41 PM
OK, I am down to less that .0005 over 5 3/8ths inches.

Set up

Start with 1" cr steel (dont know which kind) in a collet. Both cuts where done with out any kind of center. Total stock length on the first try was about 4.5 inches. 2nd round was a hair over 5.5 inches. I am using HSS with very light cut. I did notice that my finish was sometimes better with heavier cut, but for measurement sake, I thought light was best to avoid deflection.

Anything wrong with that or should I try something different??

02-20-2005, 09:16 PM
It sounds like you're pretty far along and maybe done by now, but....

Lathe alignment has been discussed in numerous previous posts. You can run a search for "lathe alignment" and come up with all the material you'd like to read on the subject in previous posts in this forum. However, one method in particular that seems to be fairly popular is called "Rollie's Dad's Method". The link for it is at:


I'm not sure how to make the link active, so you may need to copy it into your browser.

02-20-2005, 09:26 PM
Using a 12" precision level, the headstock end & tailstock end of the bed should both be within one mark (0.0005") of each other. As long as the tailstock isn't offset, there should be zero taper.

02-20-2005, 10:56 PM
with in 1 mark on the level??? Damn, I was going for perfect when I set it up. Didnt know I had that much play.

Using a Starrett 98 12".

02-20-2005, 11:10 PM
One LITTLE mark, you know. It gets really touchy beyond that.

02-20-2005, 11:15 PM
I know how touchy!! I spent 2 hours getting to about that one mark and then another hour trying to improve on it with only sum success.

02-21-2005, 08:59 AM
1" is too small for this test. Most similar tests I've seen use 2" stock as a minimum AND a razor sharp cutting edge with small nose radius, light finishing cut. I've used 2" 6061 for alignment tests.

One thing I found real handy is that after your finishing cut, place a 0.0001" indicator horizontally on the piece, exactly on center line. The tailstock end of the bed can now be adjusted for "minor" twist while watching the indicator. This took me to 0.0001" in a 7" test span, at which point I quit for a while http://bbs.homeshopmachinist.net//wink.gif Den


02-21-2005, 10:47 AM
I originally set up my SB9 on a piece of 8" channel iron under the feet. This gives a rigid reference surface that isn't going to change and greatly improves the rigidity of the entire lathe. I then used shim stock under the tail foot to adjust out any twist in the ways. I recently went through a complete re-alignment just to check and if possible improve the accuracy. I was able to get it to .0005 or so over the entire center to center length. The channel iron makes a BIG difference to the rigidity and ability to take cuts with no chatter.


[This message has been edited by Evan (edited 02-21-2005).]

02-21-2005, 01:14 PM
I sorta did the same thing on my SB 10-K (under motor drive). Ran a length of 2 x 2 x 1/4" wall square tube to tie together the little "mounting tabs" that were meant to rest on the floor. Then put machine levelers under the 2x2's. As Evan said, makes everything more rigid, much easier to level. Still spend two hours doing it, but half that time is spent opening & consuming "refreshment".

02-21-2005, 01:27 PM
I have a floor model South bend 9" Model A. I have heavy angle iron on the supports between the legs, making a shelf. I have loaded this shelf with hundreds of pounds of metal stock. The extra weight helps alot. Gary P. Hansen