My Bur King grinder seems to be possessed

[Tom Lewis]

Well, not really, but it is acting strange. Let me say that I know very little about electric motors except you plug them in and turn them on.
I have had this Bur King grinder 28 years. Lately it has began to change rpm on it's own. It is variable speed, but sometimes the rpm goes up and down without me turning the speed dial. I first thought this was my imagination, but now it is very pronounced and not my imagination.
My concern is that the symptoms might mean that something is wearing out and that maybe damage is being done. The change in speed really doesn't bother me that much.

Any thoughts from those of you who know about electric motors will be appreciated.

 

[12345678910]

28 years is a lot of dial twisting

I'd consider shooting some contact cleaner into that
https://www.google.com/url?sa=t&rct...otentiometer&usg=AOvVaw3P7zw_MTH4A2p955e3A7ty
Potentiometer
but it's probably cheaper to just change it.

Open the controller and show the numbers stamped into the pot.

Considering it's DC, does it have brushes ?
When is the last time you changed them ?

 

[AVigil]

I have had that happen on my lathe. What I found out was the brushes to the motor wore out and once replaced it ran fine.

I have had to do that a couple of times over the years with it.

Have you ever replaced the motor brushes in 28 years?

 

[Stacy E. Apelt - Bladesmith]

Brushes !!!

 

[Tom Lewis]

Thanks for the answers and help. I have never replaced the brushes. I have other grinders so the Burr King is not used full time. As for the speed dial, I never use it. I have it set to the speed I like and leave it there.
Sounds like I need to replace the brushes.

 

[Drew Riley]

Almost certainly the brushes. If they happen to not be completely worn, they (and the comm) probably at least need to be cleaned. I’d get a new set either way.