Sunday, November 23, 2014

Variable speed lathe using a DC treadmill motor

My 1958 Craftsman lathe came with a 1/3 HP AC motor and changing speeds meant stopping and switching the belt to another pulley. Blech! A little research yielded a cheap solution -- a treadmill motor. Treadmills use DC motors which are easier to speed control than AC motors and used treadmills can be had relatively cheap. Components to the system are the DC motor, motor controller (PWM), potentiometer (pot), switch, fuse, and usually a choke (transformer).

Wiring is simple as seen in this schematic.

The motor controller converts AC power to DC, the choke smooths the power and gives the motor better performance. The potentiometer is an ordinary linear taper from Radio Shack. The most common controller is the MC-60. I believe all controllers are adjustable for high and low speed but I found no need, the default settings were fine.

Control panel that houses the controller, switch, and pot.
The switch plate is a bit garish but fun.

I designed a speed chart to go around the potentiometer. To see how I determined speeds, see my post on a shop made strobe tachometer.

Pictures of my DC motors and controllers.

1 HP DC motor
motor controller
Back of potentiometer 
MC-60 controller

1.5/2.5 HP DC motor
Your motor should come with a heavy flywheel to improve torque.

And on the lathes. First pic has messy wiring, later I made it tidy.

Same motor on my Goodell Pratt lathe.