The 4 pin locking socket will fit on a spindle, but the keyways will not engage, so you could put it on the spindle any way you like (that gives you 3 wrong ways) I have a 2.2kw spindle which I tried it on. Anyway the locking ring wouldn't screw on. I would be wary about using the Rocket offering, which are basically audio connectors and only rated up to 60 volts. They seem to be popular for stepper motor connectors though.
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Cheers, Rob