Bench Grinder Has Annoying Humming Sound

[old toolmaker]

I have a 6" Harbor Freight bench grinder. It runs fine but has an annoying humming sound even with the wheels removed. The RPM is 3450. Is this an electrical issue or could it be the cheap Chinese bearings?

 

[Ulma Doctor]

quite possibly you could have some bearings that are less than accurately ground.
i'd be surprised if there were ABEC3 bearings in it.
another possibility is that the motor is wound for 50hz and we are running 60hz in the US. it's not necessarily detrimental but is a possiblity.
the humm may be resonate vibration or possibly high rotor to stator clearance
it may also be as simple as a motor fan being too close to a housing too
but if it's new- i'd take it back if the sound is annoying

 

[TOOLMASTER]

Should go away when you turn the switch off.... starter circuit may not be disengaging

 

[kd4gij]

I have this one and it does not hum. If it is new , return it.
http://www.harborfreight.com/6-in-bench-grinder-with-gooseneck-lamp-61318.html

 

[Uglydog]

Is it secured tight to the bench?
Is the sound from the grinder itself or is there an imbalance of some sort that is magnified through the bench (like a drum)?

Daryl
MN

 

[old toolmaker]

I can pick the grinder up in my hands and it still hums. When I turn it off it just coasts "silently" forever almost (the hum goes away-so it might be electrical).

Dick
MN

 

[TOOLMASTER]

can you hear the starter turn off one it get up to speed

 

[old toolmaker]

can you hear the starter turn off one it get up to speed

No, I can't hear the starter click off once it is up to speed. I know what a capacitor sounds like when it starts and clicks off and I don't hear that sound. Do all motors have starters? This motor is 1/2 HP and takes quite a long time to come up to speed which is 3450 RPM. I understand this is normal with wheels mounted. It starts real fast when there are no wheels mounted.

Dick

 

[old toolmaker]

I have this one and it does not hum. If it is new , return it.
http://www.harborfreight.com/6-in-bench-grinder-with-gooseneck-lamp-61318.html

I have what appears to be the same grinder but a different color and no lamp. Mine was $29.99 on sale two weeks ago. For the price I think it is a nice grinder.

 

[kd4gij]

Mine is orange. They changed the color a couple months ago.