On Thu, 6 Aug 2020 10:55:31 +0100, Bert Coules wrote:

ISTR that you mentioned a speed controller, can that be "got at"
to
provide soft start on/off control as well as speed?

As it happens, the speed controller's (small) potentiometer does have a
click-off position at its closing point, but the general experience of
people who have also done this motor replacement (which is not an
uncommon procedure) is that the lathe can be reluctant to start at the
lowest speed setting: the usual recommendation is to leave the control
partly open and not use it as an on-off switch.

One would really need to see how the pot and the pot switch are
wired. It might be that you could just series connect another switch
with the pot one to give a seperate on/off function.

I don't know if switching on and immediately rotating the control to say
quarter-full would overcome that.

Probably. Is the speed controller a PWM one or variable DC volts? I
wouldn't have thought a variable voltage controller would be any good
for a lathe as the torque would be too low at low speed settings (why
it's reluctant to start at low settings...)

My original idea of a simple on-off switch between the PSU and the speed
controller, plus an overall on/off/safety cutout switch before the PSU
might perhaps provide an ideal all-round solution?

Apart from the difficulty in finding a suitably rated DC switch.
Can't remember if you stated a power for the motor but I should
imagine it's a couple of hundred watts which, at 24 V, is 10(ish) A.
24 V truck switches might be suitable or use a beefy 24 V truck
relay. Just seems a bit "messy" to mechanically switch the DC when
there is already something there doing it electronically.

--
Cheers
Dave.