How to measure internal spindle thread

[joe greiner]

You could try a wooden dowel, pencil or similar to rub on the internal thread.
The witness marks can be measured. OK for coarse threads.

Jordan

I used a wood dowel to measure the internal threads on my wood lathe, similar to MC900. No specifications I'm aware of. I shaped a very long taper, and wound it into the hollow spindle as far as it would go; then withdrew and measured pitch and approximate diameter. It's left-hand thread, and I made a similar threaded dowel to use as a driveshaft for 5rpm rotisserie motor - excellent for spray coating a workpiece without runs. Set the Reeves drive at highest speed, to reduce reflected inertia from the lathe motor, and unplug the lathe motor.

Cheers,
Joe