Field Coil Winder using a Sewing Machine Motor.

[AlanBeckett]

The Microswitch should be good for 1mS and a Reed Switch is unlikely to be substantially better. However, there may be bounce problems. Whether that causes a problem depends on the Calculator. However, I expect that's pretty well debounced.
I've got a couple of Opto Switches - slotted sort - which would be much quicker but you'd need a bit of circuitry.

Alan