# Torque contacts

Does anyone know the answer? Or is it rocket science or unsolvable?

I experienced yesterday that when the slotted screw driver head was exact fit to the slotted screw, it was easier to turn the screw. I'd like to understand the physics of it.

Is the bottom easier to turn because there is even contact, while the top is harder to turn because the force is applied to a small area which damaged the screw by shredding the contact region?

But supposed the screw is infinitely rigid and can't deform. Would they give you same effort or force to turn the screws in the top case?
(If No, so even without the small region of metal deforming under the force in the top case, fewer contacts would make it harder to turn it? Why?)

• If perfectly rigid, there is always going to be three points of contact (one on each side of the slot and one on the bottom). So the contact mechanics only change when you consider the parts as elastic, where contacts can distribute themselves along lines or areas instead of singular points. Jan 27, 2020 at 13:55