I have one of these Belt/Disc sanders from Harbor Freight.
http://www.harborfreight.com/4-inch-x-36-inch-belt-6-inch-disc-sander-97181.htmlHave any of you found a safe way to vary the speed on one of these machines? I read some articles on AC motor speed controllers. (I know a Router Speed Control, made for brushed motors, probably won't work. I don't see any brushes on this motor.) The articles provided enough information to confuse me, as the motor data plate isn't very informative regarding the "type" of this motor (shaded pole, PSC, etc.?). It lists 3/4HP capacity, 3.5A.
My plan is to try lapping the gib strips for my Sieg X2 mill using the sander. I found a web store named "Econaway Abrasives" that sells custom made sanding belts in various sizes (they have a form to input the dimensions you want) all the way up to 2000 grit, so I have some ordered spanning the full range of what they offer. But I am thinking slower speed on the belt might make things easier for me, as the shape of these strips makes them hard for me to hang onto.
I bought a replacement set of gib strips from LMS, to try this project. BTW, if any of you are still using the original gib strips like I am, which have the surface consistency of 000 sandpaper, these replacement strips are WAYYYYY nicer! They actually look machined, and in fact might not need to be lapped at all. But I wanted to try this out to see how well it would work. I had tried manually lapping the OEM strips years ago, but their odd shape, coupled with my fingers, made doing so very difficult, so I gave up. Since this sander has a stop on the belt for abutting the work piece, it may make things much easier for me, and surely require far less elbow grease.

--- I was just examining the sander and noticed the drive pulley on the motor is a bit larger in diameter than I expected. So perhaps I can try a smaller drive pulley. I don't aim to slow it fantastically, just somewhat, to allow better control while holding the strip. As it is, I'll likely have to make some kind of holder. Maybe mill a slot into a block of UHMW about half the thickness of the strip.