The sandpaper discs are available in three garnet grits: coarse, medium, and fine. All three grits are “open coat”-only 40 to 60 percent of the disc surface is cov-ered with abrasive material. This helps minimize “loading” at high speeds and extends the life of the disc.
The grit you choose depends on the work you have to do:
Coarse grit will remove large amounts of stock quickly. It can be used to bring workpieces to their approximate dimensions; however, it leaves a rough surface. If you want a smooth finish, you must follow up a coarse grit with a medium or fine grit before hand sanding.
Medium grit will remove small amounts of stock and can be used to bring workpieces to their final dimensions. It leaves a fairly smooth surface. From a medium grit, you can go straight to hand sanding.
Fine grit leaves a smooth surface. It greatly reduces the time you need to spend hand sanding, though some hand sanding will still be required to remove swirl marks and obtain a perfectly smooth finish.Fine grit can also be used to grind and sharpen tools. Caution: When using the sanding disc on the Model 500 that's not equipped with the special disc sander dust chute, place a wide scrap board on the way tubes directly under the disc. Sandpaper continually loses grit, and the board will keep this grit off the way tubes where it could scratch them. If you don't use a board to protect the tubes, be sure to clean the tubes thoroughly after you finish your sanding operations.