The great object is to harden at as low a heat as possible, so as not to injure the steel. The tool must not be treated as a blacksmith does iron, nothing like so hot, but so as to be of a dull cherry color. Steel that will not harden at this heat is poor stock. When so heated, plunge it into cold water. This will make the tool hard and brittle, like glass, so that it is not fit to cut with; you must then rub it bright on a piece of emery paper or a grindstone, and hold it in the fire for a second or so at a time, until the temper is drawn to the right degree of toughness and tenacity. This will be, for turning-tools for hard wood, of a dull blue-brown, say violet, color. Straw brown is hard enough to cut steel, and you do not want such a temper for wood in general, but for some purposes, it is desirable to have a very hard tool. When the edge crumbles, it is too hard, and must be lowered in temper; when it rounds over, or dulls quickly, it is too soft, and needs to be Many things are not held in the centers at all, but are grasped by chucks, of different patterns or shapes. This, to me, is the most satisfactory way of turning, inasmuch as it allows perfect liberty and sweep in all directions, and does not restrict the fancy or imagination of the workman. Fig. 57. Fig. 58. It is not necessary to mention what kinds of work can be done, for that will occur to every one, but I will merely give here an illustration of the facility which the chuck affords for all kinds of work. Fig. 57 is a box cover, and being held at first by the corners, permits the inside to be turned out to fit the bottom. Afterwards, whatever finish or pattern is desired, can be given to the top. There is in every lathe, a center screw, like Fig. 58, which is useful for holding work I do not design, in this little work, telling any one how to hold a tool, for it is to be presumed that at least that part of the craft has been acquired. |