Measuring torque on lead screw
I am "working" on having a motorized feed for my lathe. The VFD control
on my drill press is SO convenient that I think it would be nice on the
lathe too. The biggest problem is getting the speed range, but I also
needed to know how much torque is required, for motor sizing.
I have already extended the lead screw on the tailstock end, so I made
an adapter that fits over that and has a 3/8" diam stub. I chucked the
stub in a cordless drill, set the DOC worst case, started the lathe,
then started the feed with the drill. As it was cutting I turned down
the clutch on the cordless drill until it slipped. That setting being
too small, I increased it one step.
I then took the drill and chucked up an L-shaped rod, with a 10" free
leg. Putting the end of that leg on a scale, I very slowly pulled the
trigger and noted the scale at the point the clutch slipped. It was 1
lb - 8 oz. Times the 10" arm gives 240 in-oz, or 15 in-lb torque.
Surprisingly small!
Admittedly, this is not a very precise way to measure torque, but it's
close enough for me. I'll probably double it when I come to chose the
motor needed, just to be conservative. YMMV.
Bob
|