Ignoramus26153 wrote:
I have a 7.5 HP electric motor, with what looks like a 1 3/8" shaft
(213T frame). I will use it as an extra idler on my phase converter,
to be spun up when the main idler starts.

I would like to cut the visible part of the shaft off completely.
Cutting the shaft off would allow me to put the motor into any corner
of my garage without any enclosure, without worrying about things
wrapping around the shaft etc.

The question is how to cut off the shaft. A couple of possibilities
come to mind, one is to spin up the motor and use a hacksaw, another
is to use a angle grinder. The first seems more fun but also more
dangerous (hacksaw getting caught up in a powerful motor), the second
is less fun and may not get a cutoff as clean, leading to vibration.

Go with the grinder. It will be quicker and safer. Make the cut with the
motor off. Then spin it up and use the grinder to dress it to your
satisfaction. Should be able to get an almost lathe-cut finish.