Hack your own custom tool to remove your stuck disc.
Step 1: Background - Stuck Aluminum Disc on Sander
I have a Delta Belt/Disc Sander model SA446 with the belt in need of replacement. Usually, this is an easy fix. You would simply remove the Aluminum Disc which will give you needed access for belt replacement. The disc has a hex key set screw which needs to be loosened and then slide the aluminum disc off of the spindle.
Unfortunately, mine was very stuck on the spindle. I tried all kinds of things - and finally figured out a fix. If you have this problem, this Instructable may be very helpful.
Step 2: The Secret Is Peeling Back the Sandpaper.
After peeling off the adhesive backed sandpaper from the aluminum disc, I noticed three holes in the disc. Excellent! The three holes are spaced 1/2 inch apart. The middle one is 3/8 inch in diameter and it is currently occupied by the spindle. (It's stuck on this spindle) The other two holes are threaded for a 1/4" - 20 tpi bolt. This is excellent.
Step 3: Make a Gear Puller
This situation reminded me of trying to remove a stuck windshield wiper arm. That usually requires a gear puller. The design I hacked together is a little different from others I've seen - however it does work...
I used a scrap piece of 1/8" thick steel. I made three holes to mate up with the three holes of the aluminum disc. The two outside holes are simply 1/4" straight holes (no threads). The middle hole is internally threaded to receive 1/4-20 bolts.
I also used some nuts to help with some spacing logistics. I found using the nuts actually helped greatly because it allows for some "play" within the alignment. If I had a machine shop - I could make everything super-precise. But, I needed to go the more "hacker" route.
Step 4: Mount and Employ the Gear Puller
The two outside bolts are tightened into the threaded receiving holes on the aluminum disc. The longer center bolt is used to "push" the disc off the spindle. This is done by tightening the long bolt. Success!
Step 5: After Thoughts.
I'm really glad this gear puller worked - I was about to give up on the sander and buy a new one...
I'll be spending some time cleaning up the aluminum disc. I think it became stuck due to oxidation of the aluminum. I'll be keeping the tool in case the disc gets stuck again.
In case you have this same model - or would like a reference, I've included an exploded parts diagram for this sander.
Please feel free to ask for additional detail if you have questions.
Also, special thanks to "atenea" for a very detailed teardown of this same sander.