14 years ago
I am just doing some quick back of the envelope calculations on how
much you can torque a bolt. Let's use 60kpsi as the tensile strength,
this is just approximate. if I have a 1/4" x 20tpi bolt how much can
I torque it? I've tried calculating and I think I'm making an error
area = pi*.125^2 ~= .05 in^2.
.05 in^2 * 60k lb/in^2 = 3000 lb.
sounds reasonable enough. here's where I get into trouble
pitch = 1/20 tpi = .05
lets treat the radius as 1 foot to normalize it to ft-lbs of torque.
the advantage of a screw is circumference/pitch, which gives:
pi * 24 in. / .05 in. ~- 1500
So, does that mean I can only torque it to 2 ft-lbs before I snap it?
I doubt it. Clearly I'm making a mistake somewhere.
Of course I am ignoring things like friction, shear stress, etc. just
looking at tensile strength.