Читать книгу The Handyman's Book of Tools, Materials, and Processes Employed in Woodworking - Paul N. Hasluck - Страница 76

A good oilstone, capable of putting a keen edge on the tool, is a necessity to all woodworkers. Washita, Nova Scotia, and other fast cutting stones are useful for removing waste metal when the iron is thick; but it is seldom that one of these stones can be trusted to leave a keen edge on the tool. Turkey stones are the only stones that have the two good qualities combined of cutting quickly and leaving a good edge. Charnley Forest oilstones are slow cutters, but they are to be relied on for leaving a good keen edge. It is necessary that the oilstone should be kept perfectly level, or it will not be possible to get a true edge. The stone should also be free from grit, or the iron will be gapped in sharpening, and will leave ridges on the planed work. (Fuller particulars of the varieties of oilstones will be given later.) In sharpening the iron after it has been newly ground, the hands should be kept low to make the bevel correspond nearly with that made by the grindstone. As time goes on, when the iron is resharpened the hands are kept a little higher upon each occasion (see Fig. 195), until it becomes thick, as in Fig. 192, then it must be again put upon the grindstone. Some workers find it convenient to use two oilstones—one as a quick cutter, to some extent superseding the grindstone, the other for finishing the edge. In using the oilstone, first put a few drops of good oil upon the stone, and grasp the iron as in Fig. 196; the right hand is at the top, and the thumb and fourth finger pass under. Place the whole of the fingers of the left hand upon the iron, with the thumb at the back, as seen. Now put the cutting edge (previously ground to a bevel) upon the stone in an oblique direction, as shown in Fig. 196, bearing in mind the previous remarks on the necessary inclination. The iron should now be rubbed up and down the stone, pressing it down with both hands. If the edge had been examined before placing it upon the stone, it would have been found to show a fine white line. The object of sharpening is to remove this, which must, be done by rubbing on an oilstone. Having accomplished this, turn the iron face down upon the stone, and rub it lightly a few times (see Fig. 197). The iron should now have the appearances indicated by Fig. 198. If the face of the iron has not been kept perfectly flat, it would appear as Fig. 199, and would be of no use as a cutting iron. If the iron has been rubbed too long, a wire edge will appear and utterly spoil the cutting properties of the iron unless removed. This may readily be done by rubbing the iron alternately upon each side until the wire edge falls off. When the iron is judged to be sufficiently sharp, it should be cleaned, whetted on the left hand, and its edge tried for keenness. Some try the edge by passing the thumb gently across it, but its sharpness may be judged by looking directly at it. In a sharp tool the edge is not visible to the naked eye, while, if the iron should be blunt, the edge will be plainly perceptible as a bright line.

Fig. 195.—Plane Iron on Oilstone.

Fig. 196.—Sharpening Plane Iron.

Fig. 197.—Finishing Plane Iron on Oilstone.

Fig. 198.—Properly Sharpened Plane Iron.

Fig. 199.—Badly Sharpened Plane Iron.

Fig. 200.—Fully Rounded Plane Iron.

Fig. 201.—Slightly Rounded plane Iron.