grinding stainedThe Best Stained Glass Grinders 2020 Buyer s Guide Mar 19 2020 RPM Rotations Per Minute RPM or Rotations Per Minute tell you how fast the grinder bit is spinningValues typically range from 2 850 to 3 600 rpm The faster the rpm on your stained grinder the better Quicker rotations will help keep your edges smoother and will help push excess materials out of the way for a faster more