relies on "Is the motor in the box the same one the spec sheet is for ? "
I agree - this can be a bit of a lottery. Sales literature sometimes gets pegged to a P/N for a good while longer than the engineer who wrote the data would be happy with. Hopefully though it means you get something better than on the spec sheet, rather than worse. (hopefully).


a simple way to measure torque is to use two indexing discs (opto or magnetic pick-up) separated by a torsion spring (a thin rod or shaft). By measuring the timing difference between the indexes one can calculate the angular displacement thus the torque (the torsion rod can be calibrated statically with a simple arm and weight).
Bill that's a much more robust way of doing things. The index disc on the stepper side could also be used to check for missing steps before the stall. It's probably even possible to use a couple of parallel port inputs to feed into the halscope in EMC2 to take the readings...
Hmm I can feel a project coming on before I build machine number2!