Fig. 43.
At the commencement of this book, I alluded to lathes with traversing mandrels, and to varieties of work done by tools not generally employed—that is, those which are not used by the hand, but in connection with the lathe, and driven by belting from a counter shaft over head. I give an illustration of such a tool, in one form, in [Fig. 43]. It may be screwed in the tool post of the slide rest, or otherwise attached to the lathe, and the belt from the counter shaft carried over the small pulley. The driving pulley over head should be very large, so as to give a great velocity to the cutter, at least fifteen hundred revolutions per minute. The use of this tool is to make ornamental designs—circular carving, it might be called—on all kinds of turned work, as, for instance, in [Fig. 44], where a small box for pins or needles is shown. This box is made by putting a piece of hard, fine-grained wood in the chuck, boring the hole and cutting the thread. It is then removed, driven on a round mandrel held in the chuck, turned off round outside, and then prepared for the pattern as follows:—The design settled upon, the index plate must be brought into use, and the points inserted in such holes as will bring the pattern out right, or all the spaces equal—just as the teeth of gears are cut. The tool shown in [Fig. 43], may be any desired shape. In the example of work, [Fig. 44], it is made half round, and the pattern is called “bamboo,” from a resemblance to wickerwork. The pattern is made to break joint, as mechanics say, that is, it alternates, so that the commencement of one part meets in the middle of the other. After one course is made all the way round, the tool is shifted on to another course, and the index changed as above mentioned, until the whole has been gone over. This produces a beautiful effect.
Fig. 44.
It is easy to see that a change of pattern is produced at will, by altering the kind of tool and the index. As, for instance, in [Fig. 45], where the pattern is entirely straight. When the design is to be cut on such work, it is extremely convenient to have a pair of centers to set on the lathe, across the bed; then the flying tool is not needed, nor the index on the lathe pulleys either, that on the centers being used instead. When this box is held between the centers so as not to mar it, the handle may be turned and the work run along under the cutter, with great facility. The grooves shown in the box are first drilled at each end with a common drill, just to the corner of the drill, so that a neat and handsome finish is given; a V-shaped cutter is then put in a mandrel between the centers of the lathe, and the pulleys set going, so that when the work is run under the tool, the slot or groove will be formed. The circlet, at the top of the box, is made by a crescent drill ground very thin and made sharp—a drill like a fish’s tail, only formed on a half circle.
Fig. 45.
Of course, these methods of doing this kind of work can, as I have said before, be varied infinitely, and are only cited as applicable to a common foot lathe.