Shopsmith Forums

I have an older Shopsmith, and for a while it would just hum when I turned it on and maybe trip the breaker. But I lubricated the two shafts, installed a new 110V 20A outlet and got it running. The speed control works from slow to medium, but when I try to turn it to high, the motor slows down and then stops. Another time, the motor kept running but one of the belts seemed to be slipping so that the disc sander didn't move.

My Shopsmith doesn't have the holes to put oil in, so I just had to apply oil directly to the shafts. (I worry that some might have gotten on the belts and made them slippery?).

Anyway, let me know if you have suggestions. Oddly, I actually have two Shopsmiths and they're both having the same problem.

The electric motor in a Shopsmith Mark 5/V headstock, other than PowerPro, should always run between 3450 (rated max load) and 3600 (no load) RPM. All speed adjustment is done in the sheaves. If the motor runs slower than 3450 RPM, there are three possible cases: 1) The motor is bad. 2) The mechanical work it is being asked to do (load) exceeds its rated power (3/4 HP in old Marks, 1-1/8 HP starting in the early 1960's). 3) It is not getting enough specified electrical power at the motor. Unfortunately 2 and 3 in that list covers a lot of possibilities. If your machine lacks oiler holes in the sheaves then it likely started life with a 3/4 HP motor, Gilmer Belt drive, etc. Gilmer belts don't slip, but many of the drives have a clutch, which can slip. The lower V-Belt does not usually slip, but you can treat it with a bit of automotive belt dressing and see if things improve. (It's good for both belts if they are stiff.)

A good place to start is by considering the electrical power supplied to the Mark. A common error is to use an extension cord that is inadequate, never use 16 AWG or smaller, 12 AWG is preferred, and this can still be undersized if the distance is long. For troubleshooting purposes, no extension cords should be used. Too much wire (or too small) between the motor and the circuit breaker panel cause problems. If possible, test the Mark on an outlet relatively close to your circuit breaker (or fuse) panel. Ideally, on a 20 Amp circuit which should have 12 gauge household wiring. Inspect the power cord and wiring in the Mark. Check for anything getting hot while running, for example the plug on your power cord or the headstock switch. Heat is a sure indicator of electrical resistance. Never leave the motor powered but not spinning (humming) longer than absolutely necessary, this can damage the windings.

Excessive mechanical resistance can create too much load for the motor, especially at higher speeds. At speeds above 3500 RPM ("R" on a correctly adjusted speed control), the motor begins working much harder to spin the headstock. Bad bearings or stiff belts add to that workload. A headstock that stops spinning quickly when turned off or that is hard to turn by hand when unpowered has a problem, but these are pretty subjective observations.

- David

When I got mine it had a replacement power cord on it that I think was 18ga. It really bogged down doing rip cuts