Video Link Is At The Bottom:
So one of my Christmas projects was to build myself a 12” disc sander. I’ve been wanting to do so for a while. This is kind of an experiment, due to the motor.
I’ve had this motor for a few years. I salvaged it from a furnace — the motor was only a couple years old, so I kept it. The problem is that it is only a 1/3HP motor.
As I looked around various websites and forums and so on, I found several examples of people making 12" disc sanders. But in all of that searching, I only found one person who had uses a 1/3HP motor. All the other DIY disc sander projects that I found were built using 1HP motors.
But in the end, I decided to just go ahead and give it a try. I had nothing to lose, as I was not going to go out and buy a motor or parts. As well, I thought it would be a fun exercise.
My motor came with a split pulley -- the pulley was made up of two parts that screwed together so that you could adjust it for wider or narrower belts. I took it completely apart and reversed the one side, which gave me a flat surface to mount to a mounting block.
Before going further, I then temporarily wired up a cord and tested the motor. The motor ran smooth and quiet. More importantly, the mounting block did not wobble at all.
So I moved on and made a 12” disc out of 3/4” Baltic Birch Plywood.
I fastened it to the mounting plate and the motor nearly threw itself off the bench when I turned it on. It was a little off center, which I fixed, but that did not help.
(Later on I’ve found that plywood can really vary in density. I expected better of Baltic birch.)
So I next built a 12” disc out of some MDF shelving that was absolutely flat, and it ran much better/smoother.
I then built a rough platform for the motor to elevate it, some legs, and then I wanted to build a dust shroud (also a safety shroud) that went over and behind the disc. This required that I dust off my highschool math+geometry to figure out the angle to rip pieces at to put them on the arch.
I didn’t get it totally perfect — there were gaps on the inside — but I filled those with epoxy and they’re hidden anyways…
I built a basic sanding plaform. Since this is still a bit of an experiment, I just made a fixed non-tiliting platform.
I closed in the bottom and back, and added a hole for my shop vac to do dust collection.
And wired up a switch.
One thing of note is that this motor is reversible. I am tempted to add another switch so that I can reverse direction. That may be more effort than it is worth. Though I did see one comment online from someone who claimed that his sandpaper lasted longer by being able to spin either way.
And here it is in action. It’s not 100% flat, but close, and it does seem to remove stock quickly and without burning. (I mounted a 60 grit paper)
Ask me again in a month or two. I plan to report back on how well it has been performing. The dust collection, simple as it was to set up, seems to be nearly 100%, which is great.
I’m very happy with how it turned out. It went together pretty quickly, and I’ve got a functional disc sander. And best of all it cost me all of $5 plus tax, and that was for the sanding disc. Everything else was shop scraps.
There are a few more photos and details on my website, if you’re interested.
Or you can watch me build it on youtube.