My First Threading Operation

I'll have to check it like that.
So if you can get the motor to turn but you can slow it with your hand, that means the field and the armature are almost touching because the bearings are worn?
When I go back to the shop tomorrow, I'll check that.
I was thinking that my belt is just old and needs to be replaced.
I guess I'll find out.
Thnks flutedchamber
 
That can be one of the causes of a hum. There can also be dead spots on the armature. If the motor stops on a dead spot it will hum..but not turn. I understand that this is not what is happening to your unit, but just some additional info.

I assume the motor has plain bushings in it..not ball bearings? Sometimes someone will over oil the bushings causing the motor to foul with oil and accumulated junk..brush residue and such. Ball bearings will usually sing if they are bad, long before they wear enough to cause your problem. But..bad ball bearings could make the motor hard to spin..which would also cause your hum. The hum will make your motor hot fast so be careful.
 
I think this happended once before. I left it alone for a couple of days and I must have forgot about it because when I came back, it worked fine.
I touched the motor yesterday while I was playing with the adjustment of the belt tension. It didn't feel abnormally hot to me. But I wouldn't be surprised if that motor was just starting to show signs of wear and old age. I'm not sure but I think that motor is the original motor.
Do you know how to test a motor?
Ed
 
Is this a brush style motor?

To test the bearings remove all belt tension and the belt. Try to move the shaft up and down or side to side..not in and and out..that's endplay. There should be almost no detectable movement. If there is movement put an indicator on it and see how much it is. Most likely it will be the top of the bearing if the motor mounts under the headstock (follow my thinking?) because of the pull of the belt.

Electrically testing the motor is not hard.
 
Got it. That sounds easy enough.
I'll check that in the morning.
And yes. I would like to know how to check it elelctrically ... in case you were willing to teach me.
I've always wondered about testing motors.
Ed
 
You haven't said what type or voltage the motor is. I'm assuming it's not 3-phase. What is the HP? Does it have a capacitor hump or two on it? One means capacitor start. Two means capacitor start/capacitor run. If the cap is out-of-spec, it might not be shifting the start coil's phase far enough to bring it up to speed, but it might still turn. As mentioned, that will be hard on the run coil and lead to it's demise.
 
Last edited:
Hey there,
I checked the motor pulley like flutedchamber said and it's not loose. There's no end play so I think the bearings are OK. I tried to slow down the motor while it was running-no way. So I'm thinking that the motor is still OK.
Hawkeye asked what kind of motor I have. I don't know who makes it but it is a 3 phase, 3/4 HP motor. I have a static phase converter hooked up to it.
I'm going to try cleaning my belt tomorrow because it's slippery on one side. I'll see what happens next.
Ed
 
The motor on a static converter is only putting out 2/3 of the horsepower. As stated, probably the cause of your hum..
 
Yes I think the motor is probably OK.
However, I cleaned my belt with Jet-A and let it dry in the sun. It got better but it still slips. I also tried to clean up the cone pulleys a bit.
It seems I can only make light cuts. If I go more than .005" on a cut, it starts to slip.
I wonder if my cone pulley needs lubrication.
Ed
 
If the belt isn't greasy a cleaning is OK, but you should also deglaze the belt. Fine sandpaper crosswise or at a 45 * angle will work, but a piece of coarse Scotchbrite works better.

Ditto for the pulleys. Lube the shaft(s), then clean the pulleys with a degreaser (Walmart carb cleaner on a rag works fine) and deglaze them the same way as the belt.

Once the belt slips it polishes the surface and the coefficient of friction drops. As long as the belt isn't cut or oil contaminated it can be brought back to life in most instances.
 
You must log in or register to reply here.
Back
Top