To check out your switch theory, remove the remains of the switch, tie
the two wires to the switch together, see if the unit starts up and runs
normally. If that works you can order the parts from HF (use the new
model number, the switch is pretty much a universal fit) or you can
replace the switch with an aluminum plate and a heavy duty toggle
switch. You want a SPST switch rated at least 10 amps, 20 amps would be
better for a motor circuit.

Dave, I can't do that wrote:
Hi people,

I have an old HF 4" x 36" belt sander that has provided probably 12
years of reliable service. This afternoon, just when I really needed
it, smoke escaped from the switch at turn on.

The motor and everything else works fine but the switch is mushy and
smelly.

This is an older unit and does NOT have a cap-can on the outside of
the motor. Instead it has a small device with a coil of quite heavy
copper and a black bakelite surroundings. I assume this is some sort
of delay for rotation direction at start up.

I thought I'd just buy another one but even HF want $70-bucks and a
little out of my league at the moment. Can someone please tell me how
to wire a switch into this thing?

I think the little coil and bakalite thing are OK as the smoke came
out of the switch itself and now it feels like there is nothing inside
the switch..

I have a picture of the setup but not sure where to post it.

Dave