Q. Thanks for your answer involving dull sandpaper and changing the belts more often. Indeed it seemed to have helped. What do you think about taking an old belt and turning it around so it spins the other direction? Wouldn't this expose a sharp sanding mineral; that is, I am thinking that the leading age of the mineral will dull, but the trailing edge would be sharp, so reversing the belt means sharp mineral. Okay?

A. This sounds like a good idea, but.... The mineral we use for sandpaper actually fractures during use and the fractures mean that new sharp edges are exposed. Also, the mineral wears down, so it does not stick up as high above the adhesive that glues the mineral to the sandpaper backing. So, the back edge of the mineral is not really sharper or higher than the front edge after the paper has been used.

What does happen, however, when the belts are reversed before they get really dull, is that the loading is removed, exposing more of the mineral. Loading is the technical term for having some of the wood heat when sanding, melt a little and then cooling and depositing this melted wood in the space between the mineral particles. In other words, reversing the belts partially cleans them in some cases.

Jumping ahead.... you should be able to judge when paper is getting dull in that more electric current will be required to maintain the belt speed. Further, the temperature of the wood will begin to increase as the paper dulls. So why not have sensitive ammeters on belt motors? Why not use a temperature "gun" to monitor the wood's temperature immediately as the pieces leave the sander? More current or more heat means it is time to change the paper.