Lowering Lathe Speeds With A Rheostadt. OK idea? Bad idea?

[KIMOSABE]

I had an earlier thread asking about a Jet wood lathe, and one of the things that people get concerned about is that some lathes do not have a slow speed that is as slow as they would like it. Turners doing outboard stuff seem to prefer to be able to get down to speeds in the

300's.

The lathe I'm looking at has a bottom speed of about 550.

Question: If I put a variable resistor in line with the motor to cut the voltage when I need a low speed, would that do the trick or would that be bad for the motor?

[Nova]

A rheostat will work with a universal (AC/DC) type motor but will burn out an induction motor. Jet lathes have induction motors.

[Leon]

IIRC you have the 1236? The one with a lever with about 6 detent stops? If so, you can pull the lever out on the lowest speed and push the lever down farther. You just have to tie a piece of rope around the lever to hold it in that position. I can get mine to go pretty slow in that position

[-MIKE-]

It's because it has that variable pulley that expands and contracts, right?

I'm going to try that, as soon as I hit send. Any idea of the rpm with the rope trick?

[Leon]

I determined all of the speeds by turning the shaft and watching how many times the motor fan turned for each shaft revolution. IIRC the motor spins at 1750ish.

I forgot to determine the speed at the lowest rope setting. Be sure to have the motor running when you adjust to the slow setting using the rope, obviously.

My lathe has speeds 1,2,3,4,5, and Fast. It would have made just as much sense had they indicated, Pretty Slow, Not As Slow, Slow, Medium, Faster, and Fastest. Anyway, ;~) I calculated, 1=573, 2=860, 3=1251, 4=1529, 5=2293, and Fast =3058. I'm sure that things were not perfectly aligned when I did this but I am pretty confident that I am accurate give or take 5%.

[Martin H. Eastburn]

A variable resistor will not change the speed of a motor. It is intended for a light bulb.

Speed controls are for some small motors and expensive speed control for large power motors.

I think you would want to put in a DC motor and a DC control. Or - a variable frequency controller that are used for power motors.

Martin

KIMOSABE wrote:

[Mike M]

Was watching a Del Stubbs bowl turning DVD the other night he showed how on a general with reeves speed control he rigged a foot pedal with pullies to work as a clutch on a hinged mount motor.

Mike M

[Jay Giuliani]

If it is a DC motor, a heavy rheostat might work.

If it is an AC motor, look at one of the electronic pulse type speeed controls. make sure it is rated for the motor though.

Or hit the Grainger catalog and replace the motor with one that has multiple windings for different speeds and use a multi position switch.