"Ignoramus3975" wrote in message
...
OK. All good points.

My plan is as follows;

1. Replace the three jaw chuck with welded on jaws (something weird)
with a four jaw chuck, which I also have.

2. Somehow, align the tailstock so that it is on center (not yet sure
how).

3. Make one more cut with the four jaw and tailstock.

Don't involve the tailstock in this test. Regardless of the condition of
the machine, if the tailstock is not dead concentric and in a common plane
with the spindle, it will yield results that are not in keeping with what
you're trying to establish-----if your machine can generate a straight turn.
Do this with no support on the outside of the material-----no support of any
kind.. Not a follow rest, not a steady rest. Use large diameter material
to minimize defection, and insure that the chuck is not allowing the
material to move with tool pressure.

Once you know your machine is cutting straight, you then use the machine to
align the tailstock by either using a test bar, or by machining a long piece
between centers, moving the tailstock such that you eliminate taper. You
must do the free machining first, otherwise you won't know if the machine is
right, or not.

Do not run the center with a part that is chucked. If there is the
slightest misalignment between the spindle and the tailstock, you'll
generate a compromise of not only straightness, but diameter. You may also
generate a three lobed or four lobed cut, depending on the rigidity of the
chuck and tailstock.

Harold

Harold