Bob Engelhardt wrote:
How does this work (the manual isn't clear)? Is it useful?

Bob

I put it on my Sheldon R15, as it sometimes has problems finding a gear.
This can be real handy when engaging the QC box or the back gear.
Sometimes I use it to inspect a part, or for tapping in the spindle.
I have it set for 5 Hz on the motor, so that is 8.3% of normal speed.

Jon