Paragraph 89. For a great many years grinding on a grindstone has been the standard method of sharpening chisel and plane blades. If your shop is equipped with a grindstone you will find it convenient for this purpose. Be sure to use water on the stone while grinding. The purpose of the water is to wash away the little particles of steel as they are ground from the edge of the tool. If water is not used this steel will imbed itself in the face of the stone and will thus hinder the grinding process. The water also serves another very important purpose. It prevents friction, and thus avoids heating the plane blade. Never grind an edged tool on a dry grindstone. The surface of the grindstone must be kept smooth and straight, in order that plane blades and wide chisels may be squarely ground. If it is necessary to grind a cold chisel, screw driver, punch, or any irregular shaped tool, it should be done on the side of the grindstone to avoid abusing the face. In grinding a blade, hold it at a constant angle in order to give it a true bevel, as has been explained. This angle will vary, depending upon the kind of work for which the blade is being sharpened. If you expect to do considerable rough work on hard and knotty material, the plane blade should not be ground too thin; that is, there should be a thicker bevel than if you were preparing it for soft wood or fine finishing purposes. A very satisfactory angle for a general purpose plane is about 27 or 30 degrees. When you remove the blade from the stone to examine it, be sure to put it back in position at exactly the same angle.

You cannot completely sharpen a blade on a grindstone. When the bevel has been completed and all of the nicks have been ground out, you will find the cutting edge is very rough and will possibly be turned up slightly in the form of a wire edge. This indicates that the grinding is done and that you should finish sharpening the plane blade on a whetstone.