|Project by Quietflyer||posted 03-31-2012 02:26 AM||7233 views||31 times favorited||20 comments|
I picked up a couple of these 1 hp treadmill motors from Princess Auto (a Canadian discount auto parts/tool/surplus/everything store) on sale for $20 each and figured I should do something with them, so here we are.
I designed this sander, stealing ideas from the sander built by John Heisz (ibuildit.ca). His is a little more complex than mine in a few ways.
The disc on my sander is made from an Ikea shelf I picked out of the scratch and dent pile for a dollar or two. It is then mounted onto a split bushing, which is then mounted onto the treadmill motor. I had to drill and tap a hole in it for a set screw, since the bushing is designed to use a keyed shaft, and the motor was designed to use a set screw. Not a big deal, except that on the first few test runs, the set screw would back off the slightest bit and the disc would start “migrating” on the shaft. A few drops of superglue on the set screw solved this problem.
Other than the motor cover, the rest of the sander is made from baltic birch ply, a mixture of 12 and 18 mm.
I made the table rather huge, just because I could. Its 18 mm birch ply, and I put a stiffener along the bottom. By gluing up the whole thing while it was clamped firmly to my table saw table, I managed to get a pretty flat and true surface. The table is mounted to the body of the sander using a piano hinge. Several disc sanders I’ve seen online (including John Heisz’s) use complicated trunnions to keep the edge of the table close to the disc at all table angles. I didn’t bother with this, since I figured probably 90% of my sanding would be with the table at 90 degrees to the disc. I also didn’t add a mitre slot, figuring most of the sanding would probably be freehand. If I need one, I can always add it later.
The trunnions are 12 mm ply. I cut the slots using a spiral bit on the router. I made the handles out of some scrap cherry and some carriage bolts.
I added a curved MDF “ramp” in the base on the downward side of the disc to improve dust collection. With the guard and ramp installed, this machine moves quite a lot of air on its own. I was surprised! With a shop vac attached to the collection port, there’s virtually no dust put into the air.
The guard over the disc is made from many segments of 12 mm birch ply, glued to a 12 mm ply back panel.
I put two coats of water based poly on the whole sander, and two extra coats on the table top (figuring it would see hard use).
The switch is a standard household light switch. I’m proud of having wired this thing up without burning/shocking/melting anything, since my electrical skills are poor at best!
I’m quite pleased with the performance of this sander, and I figure I spent about $100 in total, for a tool that would cost $250-300 if purchased new from a store.
The second motor may or may not be reserved for a band saw ;)
UPDATE: I never thought I’d get this much interest in my disc sander! If people would like, I can try to clean up my CAD drawings a little, and I can post them somewhere. They won’t be complete step-by-step plans by any means, but they might be useful to someone trying to build a sander.