On Sun, 3 Aug 2014 05:07:58 +0000 (UTC), Baxter
wrote:

wrote in :

On Sat, 02 Aug 2014 16:18:55 -0400, wrote:

Wrong. The friction on the threads is quite relevant.

In FACT, hitting a screw on the head while turning it is a well known,
shop worn method of removing a stuck screw or bolt.

No, that is NOT how screw removers work.

That device is not what is termed a "screw remover". I have to side with
clare on this one - I have such a device in my toolbox - albeit for metal
and not wood, but the principle is the same: you insert the tool into the
screw head, apply torque, then hit the end with a hammer. The tool has a
heavy spring inside and a spiral mechanism - when you hit it with a hammer,
it applies more torque than you can apply with your hands - plus vibration,
etc.

This sounds like an impact wrench. The impact of the hammer is
converted to torque. There is some advantage hammering to break
metal-metal binding (essentially a "weld") but you're applying torque
constantly. The impact only increases friction for the milliseconds
of the impact. Sorry, physics doesn't care about consensus.