Thread: Motor problem

  1. Want to swap the single phase 0,75kW/1HP motor in my MD-30 mill for a 3 phase one so I can use the inverter I bought.

    The current motor has a 19.8mm shaft (as best as I can measure without taking it out), a footprint of ~ 140 x 105mm and a centre to base height (I assume thats measured to the bottom of the foot) of ~90mm. The latter two measurements suggest this is a 90S frame motor, yet the 0.75Kw rating and the 19mm shaft confusingly suggest a 80 frame. The motor casing is 275mm long, which also suggests an 80 frame (90 frame being 325mm as far as I can make out). Most 1hp motors come as a 80 frame except 6pole which are a 90S frame, but this is a 4 pole motor.

    All the .75kw/1HP motors on eBay seem to be 80 frame. I suppose I could get a chunk of 10mm aluminium plate to make an adaptor but this seems an expensive option on top of the motor. Or have I got a strange motor somehow.

    Anybody else (Bill?) with a similar machine (RF-30, etc.) shed any light on this?

  2. The shaft on my motor is 22mm (actually 21.98 with wear) x 58mm. The motor casing is roughly 250mm long x 180mm diameter. 1ph 2hp , 1480rpm

    There's plenty of room back there so if you're prepared to drill the mounting plate, I guess almost anything could be made to fit.

  3. Quote Originally Posted by BillTodd View Post
    The shaft on my motor is 22mm (actually 21.98 with wear) x 58mm. The motor casing is roughly 250mm long x 180mm diameter. 1ph 2hp , 1480rpm

    There's plenty of room back there so if you're prepared to drill the mounting plate, I guess almost anything could be made to fit.
    A 2hp in a non-standard shaft size (should be 24mm x 50mm if its a 90 frame).

    Looks like I'll have to take this one off and measure it properly, then put it back so i can use it to make the mounting for the new one... then take it off again...

  4. #4
    Early mill / drills had an assortment of motors and frame sizes as they had not worked out at that stage who to copy :whistling:

    Standard motor sizes are 11 mm, 14 mm, 19 mm, 24 mm, 28 mm, 38 mm, 42 mm etc

    Then there are specials [ as always ] Bridgeport, that bastion of American technology, standardised on 22 mm diameter with a 7mm keyway for the step speed and a step shaft of 29mm and 28mm for the Varispeed with again a 7mm keyway.

    Irving, instead of a flat alloy spacer just stand it off on 4 spacers or even 4 M12 nuts like everyone else does. lol
    John S -

  5. Thanks for that John. I'll turn up some spacers on the lathe, I need the practice!

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