Hi, blackbob-ga:
Yes, this would usually be the case. For the sake of discussion,
let's imagine the screw has a vertical axis.
The actual torque to normal force relationship depends on the "pitch"
of the threads (angle of inclination of threads to the "horizontal")
rather than on the fineness/coarseness of the threads per se.
But normally the pitch of coarse threads is greater than than of fine
threads. Using a very small pitch gives the greatest leverage, ie. to
attain a torque of 100 foot pounds requires a normal force of that
times the cotangent of the pitch angle. The smaller (flatter) the
angle of inclination (pitch), the greater the leverage.
It might help to think of the other extreme, with "threads" running
straight up and down. Applying any torque whatsoever produces no
normal force because the thread surface is "vertical".
regards, mathtalk-ga |
