Lathe alignment issue

[Harry Knutz]

Sounds like the tailstock, Here is a good tool from Edge Precision to line it up.

 

[Harry Knutz]

You can also purchase a test bar to check head alignment, But I'm also leaning toward the tailstock.

 

[RJSakowski]

It is definitely not the spindle. An indication of a spindle problem would be runout at the spindle. Even so, when you run the two collar test, you are cutting new surfaces that are concentric with the spindle axis.

I would agree that the problem is at the tailstock. Either the lathe bed has a twist or wear so that moving it to a new z position shifts it in the x position or the quill axis is not parallel to the spindle axis.

On older lathes, this is a potential problem and just because you have the tailstock centered on on the spindle axis at one position for the tailstock and the tailstock quill doesn't mean it is centered for all.

 

[Harry Knutz]

When it comes to leveling a lathe, You don't really need it to be level with the earth unless you are running coolant, You could put a 2x4 under one end of it as long as you get the twist out of the bed. So If you just leveled the lathe front to back, side to side without checking for twist in the bed, Then this could also be your problem. A quick way to check is to roll your carriage all the way up to the headstock, Place a level on the carriage/saddle, Then roll the carriage to the end of the lathe checking for movement of the bubble.

 

[homebrewed]

Just to expand on RJ's comment, you can check for twist by checking the runout at a number of z axis positions. I've done that on my lathe.

If you don't know the source of the problem you are just wasting your time with "fixes".

 

[Pete301]

Just to expand on RJ's comment, you can check for twist by checking the runout at a number of z axis positions. I've done that on my lathe.

If you don't know the source of the problem you are just wasting your time with "fixes".

Thanks for all the advise. So I started checking out the tailstock. After cleaning it and checking for burs I remounted it on the lathe. I put an indicator on the carriage and extended the quill as far as it goes, about 2.25”. I traversed the OD of the quill with the indicator by moving the carriage towards the headstock. Yea, I got a problem. Indicator reads minus .003. I’m assuming that the quill bore is concentric with the od of the quill. So the tailstock axis isn’t parallel to the spindle. I figure my next step will be to see if I have bed twist or if the issue is with the tailstock. Does that seem right to you guys?

 

[Provincial]

If your tailstock bore is higher or lower than the spindle axis, it will cause a taper. If it is high or low, and you adjusted the tailstock left or right to eliminate the taper, it will be accurate at that point on the bed, but not another. This is because the further you get from the headstock, the more the taper will change.

Put a good dead center in the tailstock and compare it to the tip of the center in the headstock. They should like up exactly. Up, down, left, and right. This will be your starting point.

 

[Tozguy]

I traversed the OD of the quill with the indicator by moving the carriage towards the headstock. Yea, I got a problem. Indicator reads minus .003

Does the tailstock quill have a lock?

 

[Pete301]

Does the tailstock quill have a lock?

Yes it does have a lock. No variation in reading between locked, unlocked.tho.
I checked for bed twist and unfortunately found some. Not sure why my level didn’t show it. I found the twist by mounting two indicators on the carriage and having them run along the tops of the prismatic ways. Logan planed these tops in the same setup as flat ways. So it seemed liked a good unworn reference surface.