Noisy Lathe

compact8 said:
OK, I just made a simple tool to remove the bolts with weird heads. Turns out to be just a piece of cake.

motor%2Bbolt%2Bremover.jpg

As expected the motor is just a simple AC squirrel cage motor which are supposed to be very quiet :

motor%2Bcage.jpg



motor%2Brotor2.jpg

motor%2Brotor1.jpg

Visual examination shows nothing wrong. I really don’t understand how the noise is generated.
Click to expand...



If the armature does not run exactly true in the rotor, you can get a vibration or frequency from the motor which is noticed in the form of noise.
If the motor is attached to a surface, the surface can act like an amplifier making it sound much louder. Using good rubber mounts to prevent motor to surface contact can reduce the noise. Other than that, and new bearings/bushings don't help, then a new motor is another cure.
I would try a motor repair shop first.
 
I wouldn't waste time or money with a repair shop, given the cost of that motor new, or one similar, its most likely far less than a repair shops labor rate, definitely shop around, obviously changing the bearings yourself is cheap and something you appear to be able to handle without issue whatsoever.
 
Or, better yet, toss the motor and replace with a 3-phase motor and VFD for easy speed adjustment and smoother operation. Fractional HP 3-ph motors can be cheap on eBay and VFD will be about $150.

But I also noticed you tested your old motor with the pulley still on. How do know the pulley's any good?
 
In your picture that shows the Rotor (NOT Armature) out of the motor, I see a few problems.
The Green coating on the Right hand side of the Rotor is rubbed off.
This indicates to me that you are experiencing slight contact between the Rotor and the Stator core when energized.
The Rotor may spin freely when not under power, but the magnetic field generated when it's running will pull it off center and cause it to drag.
Which explains why it doesn't make the noise as it coasts down to a stop.

Also the bearing on the right hand side shows discoloration on the outer race, this is because the race is actually rotating in the Endbell bore.
Poor machining tolerances on Chinese motors causes this problem on a lot of their products.

By carefully measuring the bearing OD and bore ID you'll find your problem.
The Airgap between the Rotor and Stator is usually around .004", so you don't have much leeway here.
If the difference in OD/ID is not excessive (should need to be lightly tapped into place), you may get away with applying Loctite to the OD of the bearing and reassembling the motor.
Try fitting the Endbell to the Rotor without the Stator, if it slips on easily, Bingo you have your problem.
(Check the fit of the bearing/bore on the drive end as well), but the way the Rotor is marked indicates to me the problem is most likely confined to the one end.
You may be able to add a very thin shim stock around the OD of the bearing if it's way off. Loctite it in place.
My father owned an electric motor shop for over 50 years and I spent many years working for him.
Sorry for the long winded reply, but I tried to explain it as best as possible.
Good Luck
Tommy
 
Tommy's reply above is 'spot on'. Also, as above loose laminations will generate noise as well as anything loose and mountings sometimes will amplify vibration related noise. Occasionally a brand new motor will have a higher than normal sound level. ( compared to other identical ones of the same manufacturer) Also, I have noticed before that different capacitors will sometimes change the sound of a motor. (assuming a capacitor run motor) All of the above is good advice, but I would bet on Tommy's reply being the solution in your case. Keep us posted on your results.....
 
consider replacing the motor with a treadmill motor and variable speed controller that comes with it. check craigslist to find one locally

EDIT: But it would be best to repair what you have first if it can be fixed.
 
Last edited:
9Sec93LX said:
In your picture that shows the Rotor (NOT Armature) out of the motor, I see a few problems.
The Green coating on the Right hand side of the Rotor is rubbed off.
This indicates to me that you are experiencing slight contact between the Rotor and the Stator core when energized.
The Rotor may spin freely when not under power, but the magnetic field generated when it's running will pull it off center and cause it to drag.
Which explains why it doesn't make the noise as it coasts down to a stop.

Also the bearing on the right hand side shows discoloration on the outer race, this is because the race is actually rotating in the Endbell bore.
Poor machining tolerances on Chinese motors causes this problem on a lot of their products.

By carefully measuring the bearing OD and bore ID you'll find your problem.
The Airgap between the Rotor and Stator is usually around .004", so you don't have much leeway here.
If the difference in OD/ID is not excessive (should need to be lightly tapped into place), you may get away with applying Loctite to the OD of the bearing and reassembling the motor.
Try fitting the Endbell to the Rotor without the Stator, if it slips on easily, Bingo you have your problem.
(Check the fit of the bearing/bore on the drive end as well), but the way the Rotor is marked indicates to me the problem is most likely confined to the one end.
You may be able to add a very thin shim stock around the OD of the bearing if it's way off. Loctite it in place.
My father owned an electric motor shop for over 50 years and I spent many years working for him.
Sorry for the long winded reply, but I tried to explain it as best as possible.
Good Luck
Tommy
Click to expand...
Good Answer. I 've seen the same problem before.
 
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