Wes wrote:
Louis Ohland wrote:

Before I do something irrational, is there a way to measure the
pressure exerted on a shaft being held between centers? This will allow
me to calculate deflection.

The object to be used is a solid 1" diameter Thomson shaft that is
18" long.

I think you are worrying about the wrong thing. Tailstock pressure assuming
a ball bearing live center should be somewhere in your finely calibrated
this feels reasonable range.

The tool pressure doing some thing to an Thompson rod is going to be your
source of deflection. I hope you have a follow rest.

Wes

I'm not going to machine the Thompson shaft at all. Concept- drop the
shaft between a dead center in the head and a live center on the
tailstock and use it as a test bar. I was wondering about how much
deflection would be caused by the tailstock being tightened. I err on
the side of cross section thickness.

The normal straightness on Thompson shaft is .001 per foot, with .0005
being available. Well within the tolerance of the lathe that I'm using.