Shopsmith Forums

I went out to do some drilling at my 520 and the spindles won't turn. I flip the switch and there is a very loud hum and the spindles make small, halting turns like the motor is trying to turn them but can't. I turned it off and have done the following:
1. Verified I can turn the spindles by hand with no catching/sticking
2. Opened up the access panels/cover to look for debris
3. Oiled everything per manual

If I take the belt off the lower sheave and turn the machine on, the motor turns fine. When I reconnect the belt, same hum and halting turn.

Anyone have suggestions on what I can check? I inherited this machine from my grandpa last month so I don't know much about its history but he was fairly good at maintaining his tools.

If it fails to start but hums and then drops the breaker, the things I would check are the motor capacitor and the start centrifugal start switch inside the motor.

garys wrote:If it fails to start but hums and then drops the breaker, the things I would check are the motor capacitor and the start centrifugal start switch inside the motor.

He said the motor runs fine with the belt removed!

It is easiest for the motor to start with the headstock set to a low speed. But don't change the speed to low without everything turning. You can turn it by hand while adjusting the speed to slow. This is easiest with a sanding disc attached.

If you are using an extension cord make sure it is of heavy wire gauge. Best to not use an extension cord until you get this sorted out.

Do not leave power on the motor while it is humming and not turning for very long. This is a heating condition and the SS motors normally do not have overheat protection.

- David

mm42897 wrote:I went out to do some drilling at my 520 and the spindles won't turn. I flip the switch and there is a very loud hum and the spindles make small, halting turns like the motor is trying to turn them but can't. I turned it off and have done the following:
1. Verified I can turn the spindles by hand with no catching/sticking
2. Opened up the access panels/cover to look for debris
3. Oiled everything per manual

If I take the belt off the lower sheave and turn the machine on, the motor turns fine. When I reconnect the belt, same hum and halting turn.

Anyone have suggestions on what I can check? I inherited this machine from my grandpa last month so I don't know much about its history but he was fairly good at maintaining his tools.

?? Multiple pulses each time the motor is switched on ??

The first paragraph is a classical open start switch scenario except for the multiple 'pulsing'.

Contrary however is the 'runs with motor belt removed'.

Is it possible the start switch is a high resistance rather than normal low resistance(LIMITS AMOUNT OF CURRENT TO THE START CIRCUIT). Or a resistance(loose connection) somewhere else in the start circuit. Last and definitely least likely is a defective capacitor.

My 'money' is on the resistive something.

Thanks all. I'll probably teardown the headstock and start testing each piece.

Hey there

Did you figure this out? I had the same issue where the relay had come loose and was contacting the body. You said it works with the belt removed, so maybe the cap isn't providing enough voltage to turn the motor with the weight of the upper spindle on it.

did you find an answer to fix? I have the same problem,

just put a new to me motor (from ebay) in my headstock,

motor runs with no load,
headstock turns freely with belt to motor disconnected,

with belt connected to motor, it ether does not run just hums, or runs very slow
sometimes with little jerks,

the speed control sheave is open fully,

if I pull open the motor sheave by hand the motor will run slowly

bill,

If the control sheave is 'fully open' you are attempting to start at 'fast'.

Set it to slow and repeat and report back.

Dah,,,

Ok thanks, in my defence my main table is the digital power pro, have never used the older headstock.

I slowed it down --- (yes I rotated it while turning the speed down)
yes it does run at slow, but bogs down if I turn the speed up.
looks like something is also out of alignment as it is chewing up the upper belt....

Bill