Combine two of those mounts with one of those couplers, add two NEMA 17 steppers (the one on the right is that one), slide a baseplate underneath, sprinkle with various screws, and shazam you get a stepper motor dynamometer:
The baseplate puts the mounts 65 mm apart on the 10-32 screw centers, which is entirely a function of the coupler length, and is easy with manual CNC on the Sherline.
Changing the motors is straightforward: loosen coupler setscrew, remove base screws, slide motor away from coupler, remove mount screws. Won’t happen that often, methinks.
The general idea is to drive one stepper with a known current, apply a known resistive load to the other motor’s windings, and then plot torque vs. speed. It won’t be quite that simple, of course, but should produce some interesting data.
The Smell of Molten Projects in the Morning 