The tools used by the “old time” gunsmith for screw making were few and simple, and are now seldom found except in the shop of some “old veteran” of the trade. Twenty-five or thirty years ago modifications of these tools were used in some of the armories where Government arms were made, and even now the same principle of these tools is employed but changed in form and adapted to machinery operated by steam or other power.
Figure 72.
[Fig. 72] shows a tool to be held in the vise by the projection, and the rough form of the screw, or a piece of wire of suitable size is inserted in the hole in the centre of the raised portion, cut with radial teeth, and a screwdriver inserted in a transverse slot in the other end of the rough screw, or bit of rod; it is then rotated by a bit stock until by the pressure applied the teeth cut away the metal and so forms the body of the screw. To form the head of the screw another tool, shown in [Fig. 73] having a countersunk hole made in the centre of the diameter of the head but a little deeper, is used. The unenlarged portion of the hole in the tool corresponding to the body of the screw, which being inserted in the hole is rotated by means of the screwdriver in the bit stock, until the head is shaped in the same manner that the body was formed. Of course, different tools had to be made for different sized screws.
Figure 73.
Figure 74.
In forming the tang screw, which has the head bevelled on the under side, a tool was used like [Fig. 74]. The rod was turned into a tool in the same manner as for making a flat headed screw; then the body was inserted in the bevelled head-making tool and rotated as for making a flat head. The edges of the bevelled teeth being so formed as to become cutters upon the inner or central edges, and so reduce the screw head to that shape.
