Proper drawbar torque?

[jkilroy]

I saw a related thread on automatic draw bar closers and it brought up a question. What torque value should I be aiming for on a machine with a NT50 spindle? The drawbar is 1" x 8tpi, and the machine is a Kearney Trecker S-12 307, 7.5 hp spindle motor.

In the couple of times I have mounted a tool I just went for what felt tight with the wrench I was using. If I had to quess I would say that is around 50 to 60 ft. lbs., maybe up to 75.

[aboard_epsilon]

Now if I was faced with the situation your in .
I would take off the automatic thingy put in a normal drawbar........put a torque wrench on drawbar......tighten to what you feel is right ..and noting the torque required to do this on your wrench.
then it's just a matter of appliying this to your auto drawbar.......hope this maybe gives you different fresh aproach to the problem.......if it dont .well at least I tryed to help.
all the best..mark

[wierdscience]

50-60 ftlbs should be fine,afterall it just holds the arbor in the drive keys take all the actual torque.