On Jul 16, 1:01*am, wrote:
...
7) Thanks to the gentlemen who provided me with the formula. I found
it independently in the Machinery' Book late last night after I
posted. I should have found it much sooner if I fed "jackscrew" into
Google. Such is life :-). The figures I got was 125x multiplier
without friction. I tried to do the calculations with an assumed
coefficient of friction of 0.2 and got a multiplier of 31.5. Seems
kind of small. I haven't the foggiest what kind of force I put on the
end of the lever (3" long, BTW, the pitch is 0.151" and the pitch
diameter roughly 0.6").

Michael Koblic,

I think up to ~80% of the tightening force on a screw can be lost to
friction. Compare the torque to tighten with that to loosen.

jsw