Doki wrote:

"Ian Stirling" wrote in message
...
snip
Thinking laterally again.

I wonder why there are no drills that can be set to limit torque to
a constant factor times pressure on the bit.

This way there is not enough torque to cam out the bit.

I've a) no idea what you're on about or b) any idea what cam out is.

Cam out is the force that tends to push the bit out of the screw, as
it turns, due to misalignment, and geometry of the bit/screw junction.

This is zero with Torx and Square Drive - but can be quite high with
some sorts of cross-slot screw/bit combinations.

How would that differ from the standard torque limiter on an electric
screwdriver? FWIW, I've had luck getting rusted and almost rounded fasteners
out by using a very low torque setting and letting it hammer at it.

That can work, yes.

Basically, the idea is that you don't have a torque limiter as such -
but you set a torque/force ratio.

I.E. you push on the screw with 100g force, it will only turn the screw
with enough force to make the cam-out push 70g.
If you're not applying enough force, and the bit is likely to slip, it
simply stops until you push harder.

Especially with soft screws, once it's slipped the first time, it just
gets worse.
And causes bit wear of course.