# Question about lathe motor



## Lsmart (Jan 1, 2012)

Hi All,

I am planning on building my own lathe (blog to come) I have a 2Hp motor I recovered off an old air compressor (115V) and I am wondering if I can put a rheostat on it for speed control or if I need to get multi speed spindles for the belts. Basically wondering if putting a rheostat on will wreck the motor?

Thanks

Luke


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## crank49 (Apr 7, 2010)

Yes.
Yes it will wreck the motor.
Yes you need to use stepped pulleys.
OR, if you want to spend the bread, you can get a VS drive for an induction motor.
I might still employ a pulley reduction even with a VS drive so I could have high torque and low speed together.


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## PurpLev (May 30, 2008)

2Hp motor from a compressor makes me assume this is a induction motor, if so, I don't think a rheostat will work as they are aimed at the direct drive motors (routers and such).

for variable speed control, DC motors with a DC driver are a a more common setup. looking forward to seeing your build as I am planning on going a similar route at some point possibly (unless I find a killer deal on a lathe)


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## PurpLev (May 30, 2008)

as Michael suggested - even the VS lathes have stepped pulleys for different ranges of speeds, but you don't really get a 0-MAX complete control without losing some torque.

Another option to setup VS with induction motor is to use cone pulleys, but you'd need to build/find that drive mechanism and incorporate it into your lathe (this would probably be my path)


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## Lsmart (Jan 1, 2012)

Thanks Guys Question answered… next does anyone know a good place to get 5 step pulleys?


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## PurpLev (May 30, 2008)

what is your motor arbor size?

you can get replacement parts from Grizzly to their lathes as one option. or find a machinist to make you custom pulleys for your arbor and step sizes. where are you located?


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## Lsmart (Jan 1, 2012)

I believe it is 5/8 inch, I am located in canada, I will look at Grizzly… Thanks!


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## exelectrician (Oct 3, 2011)

globalindustrial.com

Will have the pulleys you want


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## REO (Sep 20, 2012)

the motor you have has no brushes the rheostats only work with brushed motors. The rpm of the motor will make a differance as to how deep you need to go with the reduction you could use four steps and a jack shaft. many drill presses have a third idler shaft in them to get the range of speed.


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## wormil (Nov 19, 2011)

Set the lathe up with a single speed then make step pulleys out of wood.


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## oldnovice (Mar 7, 2009)

An induction motor, one without brushes, cannot be speed controlled with a rheostat unless it is a VFD motor and drive (external controller required). Such as but any HP greater fractional will be expensive. Just the drives, no motor, are near the $100 starting price.

Even a DC motor will not give you the performance you want with a rheostat as the rheostat is nothing more than a series resistance and creates a voltage drop and limits the amunt of current available thus degrading the motor performance. If you want performance out of a DC motor with speed control you need to look a solid state speed control. Such as

*Go with pulleys, less cost and simpler to use.*


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## Lsmart (Jan 1, 2012)

looks like i might just buy a 2nd hand lathe, pulleys and vfds putting my cost up.


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## Ted78 (Dec 3, 2012)

First thing to check is if the motor off the compressor is induction or 'universal' It is probably an induction motor, but I wouldn't bet on it, a cheap, compact, or portable compressor could have a 'universal' motor on it. Check to see if the motor has brushes, like a hand drill or router motor, if it does then all you need to control the speed is a cheap dimmer switch, well maybe a commercial dimmer switch, check the amp rating.

If it was easily removed from the compressor though it is probably an induction motor, which will burn up if you try running it with reduced voltage. Universal motors are usually integrated into the tool, while induction motors are usually bolted on.


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