On 06/02/2018 21:42, Chris wrote:

Hi,

Say I do a nut or bolt up to (for example) 120ft/lbs as checked by a
decent torque wrench in calibration, can that same nut/bolt be undone by
the same amount of force, or does it take more - and if so, how much more
and why?

Assuming everything including friction etc is constant, then less as
you'll have the thread angle coupled with tension to assist in the undoing.

If there is any form of stiction, cold welding etc, then who knows.

Otherwise bolts would never be able to rattle loose or require crinkle
and/or split washers to prevent a bolt or nut from unwinding.