The stones that usually come with a grinder are too coarse and too hard for dry-grinding hand tools. Our 6" (150mm) diameter, 1" (25mm) wide grinding stones are aluminum oxide with a soft bond (grade H) and an open structure. They will wear faster than hard stones but will not burn tools as readily. With a bit of experience, you will find that you can quickly grind a nick out of a chisel without overheating the tool. Two grits are available. The 80x wheel is best for chisels and plane blades; a 120x wheel is available for carving tools. The wheels have 1" (25mm) arbor holes and four bushings for 1/2", 5/8", 3/4" and 7/8" shafts). Maximum rpm is 3820.