VFD Selection for Rigid Tapping

Couple of questions, if I may. What kind of encoder have you used with the Marathon BlackMax motor ? Did you fit the encoder on the motor or somewere else?

The motor came with a Dynapar HS35 installed, but it was a 2048-line unit which was too high a pulse frequency (at max RPM) for my input board at the time.  Would have been fine at 1800rpm, but I was spinning the motor up to 5k.

I replaced it with a US Digital E6 that was ~400/ppr (1600 post-quad).

Encoder was motor mounted (not spindle), and the 1:1.54 belt ratio was programmed in to the control.  Index signal for rigid tapping was accomplished by mounting a small plastic ring on the top of the spindle and holding it in place with a steel set screw.  The set screw triggered a fairly high frequency proximity sensor (~7khz), which was connected to the control as the index signal.

The encoder's built-in index signal was left unconnected.

I never tried tapping at really high speeds, but I did have an 'oopsie' moment and wound up tapping a 1/4-28 hole in aluminum at ~5000rpm spindle speeds.  I crapped my pants, but the spindle & Z-axis never complained.