Paragraph 90. The final sharpening of the blade must be done on a fine whetstone of some sort. This may be a natural stone or an artificial stone made of carborundum. For the finishing work use a stone of fine grit. See that the face of the stone is perfectly clean and use plenty of oil during the whetting process. Do not use linseed oil on any kind of whetstone. It will not only fail to give satisfactory results, but will render the stone unfit for use. Use machine oil, which may be thinned with kerosene. The oil on the whetstone is to serve the same purpose as the water on the grindstone.

Grasp the plane blade firmly with the right hand; let the fingers of the left hand rest on top of the blade, as shown in Figure 66. Whet with a backward and forward motion covering the entire length of the stone. Be sure to keep the angle constant. In order to do this you must not use a rocking motion. Some mechanics whet a blade with a rotary, or circular motion, but this plan is not to be recommended, for it is less likely to produce a true angle and a perfectly square cutting edge. Examine frequently to see that the whetting is being done on the extreme point, or cutting edge of the bevel; that is, the whetting will be done at a little greater angle than the grinding is done. When a very fine wire edge appears, lay the blade flat on its straight side and draw it across the stone, using great precaution not to raise the opposite end of the blade, but to keep it perfectly flat. (See Figure 67). After the edge has been made as keen as possible on the oil stone give it a few strokes, stropping fashion, on a piece of leather, which should be kept in the shop for that purpose. If this has been properly done, the plane blade should be keen enough to shave. If you have not secured such results it will be well to find the difficulty and try it again.

Figure 66.

Figure 67.