Fig. 223. Holder for Grinding Chisels or Plane-Bits.
The tool to be ground slips between this loop and the strip C, and is held firmly in place by the pressure applied to the back end of D, which thus acts as a lever on the fulcrum E.
Any desired bevel may be obtained on the tool to be sharpened, by choosing the proper hole in A for the back end of C or by adjusting the tool forward or backward in the clamp. As much pressure may be put on the tool as the driving belt will stand without slipping off.
A still simpler holder for the plane-bit only, is a strip of wood 1½" thick and 2" wide, cut in the shape G shown in Fig. 223. The plane-bit fits into the saw-kerf K, and in grinding is easily held firmly in place by the hand. By inserting the rear end of the stick G into a higher or lower hole in the board A, any desired angle may be obtained. G is shown in position in Fig. 221.
All such devices necessitate a perfectly true stone. The essential features are, to have a rigid support against which the tool may be pushed by the revolving stone, to hold the tool at a fixed angle which may be adjusted, and to press the tool against the stone with considerable pressure. The wheel should revolve toward the edge which is being ground, for two reasons. It is easier to hold the tool steadily thus, and the danger of producing a wire edge is lessened. The edge as it becomes thin, tends to spring away from the stone and this tendency is aggravated if the stone revolves away from the edge. If the stone does not run true and there is a consequent danger of digging into the stone with the tool which is being sharpened, the stone would better revolve away from the edge. The grinding should continue until the ground surface reaches the cutting edge and there is no bright line left along the edge. If the grinding is continued beyond this point, nothing is gained, and a heavy wire edge will be formed.
Fig. 224. Agacite Grinder.
A very convenient and inexpensive grinding tool, Fig. 224, sold as the "Agacite grinder,"7 has a number of different shaped grinding stones made chiefly of carborundum.
Footnote 7: Made by the Empire Implement Co., Albany, N. Y.