IT’S ALL ABOUT BEING ABRASIVE!
You will often see a grit number quoted when referring to sandpaper. This reflects the size of the particles on the abrasive. The lower the number, the coarser it is. You generally start a job with a low number, then move to higher grades to get a smooth finish. You use 40 to 80 grit paper for removing old finishes and smoothing rough timber. The most commonly used is the 120-180 grit range, which creates a smooth finish on most materials. Fine finishing work should be done with 240 grit and above. This will remove any minor scratches left by lower-grade papers.