Last year I was in need of a disc sander for a little project. I wouldn't be using it that much so I didn't wanted to buy one as they can be pretty expansive. An old electromotor from a blown compressor became the powerhouse for this project. Did I just say project? Ofcourse I ment to say 'infernal death machine' since I already lost a fingernail trying to sand a small block of wood with this deathtrap. No joking around: this is some dangerous equipment so handle with care!
Step 1: Motor and Setup
I started out with making a little table on witch I bolted the motor. I ordered 30cm (diameter) round 80 grid sandingpaper that I used to eyeball the height of this contraption. The motor is a converted 380v to 220v electromotor from an old blown compressor. Nothing fancy here, old but reliable I geuss.
Step 2: Making the Wheel
I made the wheel out of old plywood I had lying around. I just used a jigsaw so it wasn't perfectly round. I found the center by drawing a few lines and where they met I made a hole. This way I could center and bolt down the old pulley that came with the motor.
I actually ended up clamping the whole thing down next to a vice. In the vice I clamped down a chisel and with a hammer I wacked it closer and closer to the spinning wheel shaving of the excess wood untill it was spinning nicely without shuddering. I left it spinning while I sanded the edges with sandpaper. This method is not really save but it worked for me. Afterwards I made the wooden casing.
Step 3: Balancing
When I fired it up the machine was thumping all over the place. Without clamping it down to my workbench it just took of. I balanced it by boring small holes in the back of the spinning wheel. I took quite a few holes but now the disc sander is pretty stable and there is no need for extra clamping.