Looking for old Craftsman belt sander owners manual 315.22420 3x21. Probably 40 years old but I don't know it was my dad's.?

I haven't found any owners manual for the 315.22420. I also have one, likewise inherited. To change the sanding belt, press in on the front roller until it clicks and locks into a retracted state. You need to press against the workbench and lean hard on it. Once clicked into retracted, the 21 inch sanding belt will slip nicely over the rollers.

To tension the belt, you have to get the front roller to unlock. You may be able to do this by pressing in and wiggling it from side to side. Or you can back the tracking adjustment all the way out and the catch will release with something of a bang.

Reply: thanks much, that's been the key problem -- I remembered how to take the tension off but not how to put it back in tension, have been afraid I'd break something. Will try messing with the tracking adjustment.

I have the manual, can scan and email if still required.

To put tension back on the belt, the manual suggests you strike the front pulley on the side of a workbench or table or place a piece of wood over the pulley support and strike with a mallet or your hand. I just tap on the pulley support lightly with a hammer.