Speed control on a grinder?

[Aaron_W]

I've got a belt grinder on my projects list. One of the things I've noticed is most of the plans recommend a 3 phase motor and VFD to provide speed control. Alternately many suggest a tread mill motor.

I'm wondering how useful speed control really is? Lots of quality grinders round (bench) and belt use a fixed speed. Variable speed grinders actually seem to be more common on lower end grinders making me think it is more of a marketing thing than any kind of necessity.

I can see where having a couple of speeds to cover a wide variety of materials (wood, plastic, aluminum, steel etc) might be desirable on a belt grinder, but swapping pullies or using a multi-range pully seems more economically viable, and not that big of a deal unless you swap between materials frequently. Certainly less of a hassle than doing so on a lathe, where that remains a common practice.


So do you actually use your variable speed? If you don't have variable speed do you often find yourself wishing you did?

 

[markba633csi]

I think it's more of a gimmick too myself

 

[sdelivery]

I would be more concerned with the grit of the sanding belt and the material used for the abrasive.
Silicon carbide is more expensive than aluminum oxide or granite but is preferable on some materials like bronze.

 

[GeneT45]

Agree with @markba633csi. I have speed control on my burr king and almost never use it. Just turn it to 'fast enough' and everything is good. My Ellis grinder is the most used in my shop and it has no speed control (that I can think of, maybe there's a belt change or something, but I've never done it). Get where you want by changing grits. Speed control is an advertising gimmick in my book...

GsT

 

[ttabbal]

I use it, but I don't think it's required so much as nice to have. I use it more for general purposes than for tools.

 

[rabler]

I built my own 2x72, 2HP w/ VFD. I rarely change the speed and wouldn't miss it.

 

[DavidR8]

I'm building a 2x42 grinder with a 1hp Baldor motor and have not given a single thought to having variable speed.

 

[C-Bag]

This is something I've always wondered about too.

I have a belt sander on my 6' grinder that's technically called a MultiTool. It's a belt sander with integrated 9" disk sander and 99% of the time I don't run it with the belt, just use the disk and there's no speed control.

So while we're asking questions, why 2" wide belts? is this for being able to maneuver into the belt easier? Or is this just "historical engineering"(we've always done it this way)?

 

[ttabbal]

I think 2" is partly for working room around the belt. It's also inertia, so many belts are already available in 2x72 and 2x42 that unless you need a different width for a reason, you just go with 2. Wheels and accessories are very available as well. Particularly among the knife maker groups. Being able to use all of that is very nice.

One thing I do use speed control for is to increase the motor speed up to 2x for ceramic belts that like really high SFPM. There are other ways to get the same result, particularly with VFDs. The only cost was a little wire and a 5k pot, so no big deal.

 

[ChazzC]

I regularly use the variable speed on my Delta 8x1 bench grinder: I have a Scotch-Brite deburring wheel on one side and a 60 grit white Aluminum Oxide wheel on the other.