# Can you add a speed controller to stationary belt and disc sanders?



## SawTooth1953 (May 7, 2009)

I use my large disc sander and stationary belt sander to "sand to the line" after rough cutting a pattern. Too often I get burn marks. I know about taking light passes, and using a light touch, and using a coarser grit first if I have a lot to reduce, make quick passes, etc. I am also aware some woods are very prone to overheating/scorching…but who wants to avoid beautiful woods just because they aren't easy to work with?

All those tips are good but they still don't ensure a clean outcome. All the tips are aimed at trying to get the job done with sandpaper that is moving too darned fast. I conclude that I'd like to slow down the disk sander and belt sander because I'm sick and tired of getting burns in spite of all my efforts. I cannot be the only one.

So my question is: Will I ruin my tool or ruin an add-on speed controller if I try that route? (The speed reducer is the type made for routers.)

I don't know the type of motors in my tools. What I'm using is the Ridgid oscillating belt sander and the other is a large disc sander from Grizzly. At times I use a basic combo disc/belt sander and sometimes a HF 1" belt sander.

Does anybody have experience adding speed control to these types of benchtop tools? If not a router-type speed controller, than what type?

BTW, I don't recall seeing this advice before: One thing I noticed on the large disc sander is the sandpaper is flying by fastest at the outside, and slower nearer the center. Of course I'm staying on the left side so the disc direction is downward, but the point is that when sanding smaller things nearer to the center, it is a lot less likely to burn. Now I wish I could find a 'sweet spot' on a belt sander.


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## conifur (Apr 1, 2015)

I know you cant use that on induction motors, I would bet your Grizzly is an induction motor. As far as your Rigid I doubt that is an induction motor. I have one of those types of speed controls, just got the instructions out. First page, first item
WARNING
it is compatible with any universal AC/DC brush type motor 15 amps or less.
NOT for use with the following types, brushless, induction, shaded pole, and soft/slow start motors.


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## Finn (May 26, 2010)

Yes, what conifer said!

I have two 6"x48" x9" belt/disc sanders from harbor freight. They have induction motors so cannot be slowed with a speed controller but they are belted motors so are slowed a bit but not enough for the disc sander on it. I do not even use the disc sander on them because of the "too fast" problem you speak of. I use the belt sander only and can do anything the disc can do but without burning the wood. These sanders are the most used equipment in my shop.


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## wapakfred (Jul 29, 2011)

There's not much you can do to slow those down. Certain single phase and most 3 phase motors can be controlled with a VFD, but not the ones you have. I bought the Grizzly sander with a 1725 RPM motor for that reason.


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## bigblockyeti (Sep 9, 2013)

They both use an induction motor, you could control the speed with a VFD which can be more difficult to wire than a machine using a three phase motor, but not always.


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## oak500 (Apr 1, 2014)

You could try changing the belt pulley size to change the rpm.


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## MrUnix (May 18, 2012)

> They both use an induction motor, you could control the speed with a VFD which can be more difficult to wire than a machine using a three phase motor, but not always.
> - bigblockyeti


Please explain how you use a VFD with a typical single phase induction motor… I'm intrigued!

Cheers,
Brad


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## SawTooth1953 (May 7, 2009)

Is it just me, or is it crazy that companies sell sanders that give us fits by running too fast to sand without scorching the wood?


> You could try changing the belt pulley size to change the rpm.
> 
> - oak500


oak500, none of my sanding machines have belts or pulleys… If they did, I'd do what you suggested.


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## SawTooth1953 (May 7, 2009)

> There s not much you can do to slow those down. Certain single phase and most 3 phase motors can be controlled with a VFD, but not the ones you have. I bought the Grizzly sander with a 1725 RPM motor for that reason.
> 
> - Fred Hargis


The Grizzly sander with a 1725 rmp motor is the one I have that burns wood all the time…especially if I'm sanding nearest the left edge of the disc where the sandpaper is whizzing by the fastest.

Grizzly says about that sander (model G7297)- it spins at 1725RPM and
Motor: 1 HP, 110V, single-phase, 10A, TEFC

I don't know enough about motors to know if that is one that is excluded from use with the speed control 
(excluded ones were stated above as: brushless, induction, shaded pole, and soft/slow start motors.) I looked up TEFC: "A TEFC enclosure on a motor means "Totally Enclosed, Fan Cooled". This motor is probably the most commonly used motor in ordinary industrial environments."

To me, that doesn't describe the characteristics of the motor in a way that helps me answer my original question about adding a speed control. To those in the know, does "single-phase" provide the answer in some obscure way. (Obscure to me, that is!)


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## MrUnix (May 18, 2012)

It's not happening with the motor you have.

Cheers,
Brad


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## wapakfred (Jul 29, 2011)

> It s not happening with the motor you have.
> 
> Cheers,
> Brad
> ...


What he said^^^^^^. Since that's direct dive there's nothing you can do with sheaves, either. Best to search for other options. You didn't mention what grit you were running, it may be that changing to a different (probably more coarse) grit may help. Otherwise it's off for looking for a different sander.


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## MrRon (Jul 9, 2009)

Universal motors have brushes and therefore can be used with a router type speed controller. No brushes, no speed control.


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## splintergroup (Jan 20, 2015)

There are ways, but they get rather expensive. Remember that the surface speed of a disk gets faster as you move towards the outer edge. Sanding closer to the center may be enough to help you out?


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## conifur (Apr 1, 2015)

> Universal motors have brushes and therefore can be used with a router type speed controller. No brushes, no speed control.
> 
> - MrRon
> </blockquote
> That motor is an induction motor, so it cant be used with a router style/rheostat speed controller.


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## SawTooth1953 (May 7, 2009)

Thank you all for your input.

Splintergroup, yes I did find that sanding small pieces closer to the center did avoid burns.


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