Step 1: Background - Stuck Aluminum Disc on Sander
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.
Step 3: Make a Gear Puller
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
Step 5: After Thoughts.
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.