My lathe is turning a taper

Bah that didn't work. Now it's off by .020 going the other way, tailstock side being larger. I'm going to have to do this via cutting a section on both ends and measuring the difference, adjusting the tailstock as needed.

I sure hope my headstock is lined up with the ways, otherwise, I wouldn't know how to fix that
 
The way I found it easiest to precisely move the tailstock was put a indicator on the tailstock so you can see the movement. Leave the piece that you just cut in the machine,adjust the tailstock .010 in the other direction and do a cut. You might be sacrificing the piece but after done your machine should be spot on, or at least at that position. I had the lock bolt that locks the two pieces together mess me up forgetting to tighten then get measurement.
 
I think the work piece was just flexing while I was turning, and that the indicating I did before that was correct. I'll have to mess with it some more. The work piece was around .430 at 15"... why didn't I think it wouldn't flex... that was dumb of me.
 
A piece that size will end up smaller at both ends and fat in the middle due to deflection. That's when a follower rest comes into play. We all have to learn these lessons.
 
Take a look at this video
If headstock is out of alignment with bed ways, aligning tailstock will not help
 
Just curious - what kind of tool are you using? If its a carbide insert then what is the nose radius? I ask because a large nose radius will cause the work to deflect more. In this instance, a follow rest is the best option.
 
Okay, my experience with large nose radii is that they cause more deflection than smaller radii. If your tool geometry is good and the edges are sharp, a small nose radius will cut with much lower cutting forces and will therefore deflect less. If you prefer not to modify your tool then, again, use a follow rest and it will cut with a lot less taper.
 
This is something I will ultimately have to do when I have put my lathe together. I see there are many YouTube videos on exactly how to do this, including how to interpret the test bar measurements to then adjust the difference out in (almost) one step. The MrPete (Tubalcain) videos mentioned earlier look like all we need.

The quite sensitive test for whether the headstock and tailstock centres meet up exactly is to put a steel rule in between their points, and move the tailstock up to touch them together. If they are even the slightest amount misaligned, the rule will tilt. If the steel rule can be held between the points approximately 90° to them, all is well. If not, you can immediately tell which direction the (tiny) offset is.

However you fashion the test bar, even if it is a from a old pipe with end bungs, a key point is that the final cut on the dumbell-like ends, done between each adjustment, is a very minimal depth finishing cut deliberately to minimize the forces.
 
I got it to .001 in about an 8" length, which I'm happy with.

so far, doing it with the test bar I made didn't give me any success

What I did was I used about a 14" length of 1" diameter 1018 cold rolled bar. I turned a 1" length close to the head stock and a 1" length close to the tailstock. The difference was around .006

I then put an indicator on the tailstock and moved it .003 towards me.

Then I turned on the same 1" lengths, took off .010 on both sides. That got me .001 difference and I'll just leave it at that.
 
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