Why do my sander belts break? I recently made several fairly small boxes for rocks using rough cedar boards. Just nailed them together. Started sanding with my 3" x 21" sander and the belt ripped. No problem it was an old belt. Then I put on a new 80 grit belt and it popped before I had finished one box. I decided I better take off the sharp edges with a rasp first. The next 80 grit belt popped after touching the wood for less than 10 seconds. The third belt popped quicly also, and I was throughly disgusted. All belts except the first broke apart at the glue seam. I don't think the belt popping is due to me as I carefully centered each the belt, nail heads were below the wood, and I applied little pressure.
I have had this sears sander for over 20 years and been pissed before when belts broke for no apparent reason. I've wondered before and am still wondering if maybe belt tensioner (which isn't adjustable) is set way too high. Any thoughts?