I have used Drum Sanders for a long while mainly because I hate sanding. From experience, a good all-around utility grit is 80. Is not too rough and also can take some abuse and can be effectively cleaned with the sanding belt cleaner (big eraser). Pine, Plywood, painted lumber, and knotty aromatic red cedar should be a no-no as they can clog the belt rather quick. but they are doable with very light passes and 60 or 80 grit. Steamed Walnut, Padauk, Cocobolo, Yellow Heart, Blood Wood, and Bocote will clog the belt too if you take aggressive passes. Steamed Walnut at times has residual oil around the knots and or voids in the lumber and will put a nice line on the belt, sometimes it can be cleaned if you run soft maple or red oak in between passes. Apitong lumber has a lot of silica and will clog the belt making it unusable. This one you can not see as is transparent what it does it make the grit slide on top of the lumber instead of sanding. Should not be a problem as is not frequent lumber used for projects (trailer deck use). Once you move to 120 grit and above you’re looking more at a finishing sanding and more care should be used on the passes. Meaning that each pass should be less than 1/8" of a turn on the top wheel. When replacing the sanding belt, look at the back if it has arrows, the grit is directional and when installing the belt should be with the direction of the rotation of the drum which is from front to back or away from you. If it doesn’t have arrows you can install it either way. If you’re going to go through different grits on your stock, if you do a good job on the 80 grit (meaning you get your pieces evenly flat, no blemishes) the subsequent grits (120, 150, 180, etc.) should not require more than three passes on each face. You will always have visible straight lines no matter the grit used. Use an orbital sander or hand sanding with the grain to get rid of the lines. It does not require a lot of work though. If you sand across the grain, you are going to hear a loud noise (something like toc, toc, toc), depending on the density of the wood (maple or purple heart) it will overheat the drum and trip the breaker of the machine. It is not designed to sand cross grain. Incidentally, the Drum Sander in there is a workhorse, it takes a lot of beating before it breaks down and it is due to happen, if the roller bushings, conveyor switch, and the spider have not been replaced, more than likely they are going to go bad soon. They are normal wear and tear parts. It looks like the switch has been replaced.