On Jul 17, 7:53*am, " wrote:
...
This seems too obvious to mention, but I will anyway. *The friction
depends on the lubrication. *A ball bearing thrust bearing or a roller
bearing would also help....

Perhaps you could incorporate Belleville washers to give you an idea
of the force applied. *Belleville washers can be stacked to increase
the force necessary to flatten them.

* * * * * * * * * * * * * * * * * * * * * * * * * * Dan

IIRC experiments on torqueing aircraft fasteners showed a 2:1
variation in clamping force vs torque from surface roughness etc under
the best conditions. A skilled mechanic's judgement was as good as a
torque wrench. The best way to torque a fastener to a large fraction
of its yield point was to measure the change in length, though that's
not always possible. I saw that in print a long time ago.

The bottom line is you have no good way to predict what's happening
and should measure the forces.

jsw