Over engineered bench top grinder!

[idrivemopar]

So, when I was doing my restoration project, I bought a porter cable 6" bench top grinder. I didn't really need it for heavy work, just some odd and end grinding, wire wheel for cleaning up small parts, and buffer wheels for doing some of my trim work. It is the variable speed model, and worked very well for about 3 months, then all of the sudden it just stuck on high speed.

Well, I finally got around to pulling it apart thinking that the rheostat (speed control knob like the old school ones had) maybe had gone bad! To my surprise, it is very over engineered and contained a standard potentiometer for speed control and is hooked into a circuit board that has an optical sensor on one side with a slit style paddle wheel to measure the rpms of the motor. I really didn't think such a simple device needed to be fully integrated with electronics.

Fortunately it was an easy fix. I think all the buffing I did is what generated the dust and fuzz that clogged the slits on the optical sensor, and once it was cleaned its back to working like a champ.

So, just an FYI if you have one of these newer bench top grinders and it develops speed control issues, check for one of these sensors. I know several brands are using this setup.

 

[Car Nut]

Good information, thanks!

 

[fratzog lover]

Was it made in Germany? You know, why use 1 part when 7 will do! Cough, BMW Mercedes, cough.

 

[Funship32]

Was it made in Germany? You know, why use 1 part when 7 will do! Cough, BMW Mercedes, cough.

*LOL*- or as I say: Over engineered and built to stay that way.