In article ,
Tim S wrote:
b) how does an electric screwdriver achieve this?

Mine's got a torque limiter (one of the reasons I got it). Bit course
though and has no markings other than a rather arbitary 1-10 (ie no Nm
or ft-lb).

Indeed - but if you were concerned about accurate torque, you'd use a
pukka torque screwdriver. I have one for auto gearbox repairs. Manual, of
course - and pretty expensive. I'm sure you can get specialised production
electric tools that do the job - but I'd doubt many would have them at
home.

--
*All generalizations are false.

Dave Plowman London SW
To e-mail, change noise into sound.