I need to restock the sanding belts for my 3x21 inch belt sander. I only sand wood.
The belts that I've bought over the years either break apart right away, when they get hot, or as they age (like less than 2 years). Some belts broke apart after a few minutes of use even when just purchased (though I don't know how long they might have been on the store's shelf or in storage).
I remember using my dad's belt sander (like 50 years ago) and the belt joints were overlapped so had to be installed per the directional arrows. Don't remember them ever breaking apart, just discarded due to grit wear. The belts I see now are all taped so no directional arrows, and the ones I've bought so far don't last long.
What's a good brand of 3x21 inch sanding belt that doesn't break apart?
Also, what grits and grit type do you use? I've been using 50, 80 and 120 grit aluminum oxide belts.
EDIT:
I neglected to mention that I do always adjust the belt tracking so that the belts do not rub against the metal or track too far out. So that's not a cause of my belt breaking problems.