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Rheostat on polishing motor?

I have a 1/2HP, 3450 RPM polishing motor. There are occasions that
I’d like to have a 1725 RPM motor. Would it damage the motor to use a
rheostat with my current motor? Or is there another solution, short
of purchasing a different motor? As usual, your wise advice is


For most motors it is not a problem. Assuming it is a standard
direct drive then it would be OK.

Nick royall


With that sort of a speed my first thought is an induction motor.
Don’t hang a rheostat on it unless You like smoke coming out of both
pieces. Change the pulley sizes with a belt or use a jack shaft and
4 pulleys and 2 belts. Carefully, a 4 pulley one will chuck you
across the room in pieces.

Get a gentler slower motor and make another new little one. A plywood
box (or even cardboard will last longer than you think. Shove an air
suction line blowing out the window and you are good to go. Any
questions just ask, I’m not that hard to find

Demand Designs
Analog/Digital Modelling & Goldsmithing

If your thinking long term, then go for another motor with a v belt
drive to the polishing spindle via a set of pulleys. then you just
change the belt over to which ever speed you want at the spindle. I
use a 1hp motor at 1440 rpm with 3 pulleys on the motor. 4in 3 in and
2 in with the same on the spindle shaft. Obviously the 4in pulley is
opposite the 2in

Hi Jamie

Polishing motors usually use an induction motor. These are fixed
speed motors that cannot be controlled with a rheostat or any other
form of speed controller. The motors in a flex shaft are comutator
motors that actually will operate on AC or DC and their speed can be
controlled by varying the voltage of the power supply with some form
of speed controller…