These are machines of ingenious design which make a great variety of small metal objects from round, square, hexagon or other shaped rods of brass, bronze and steel. They embody a very high degree of mechanical ingenuity, and the rapidity and accuracy with which they turn out a superior grade of work is remarkable. Not only do they make all kinds of machine and other screws, particularly in medium and small sizes, but they make an endless variety of small articles too thick or intricate to be made by the drawing and spinning processes mentioned for shaping sheet metals.

Fig. 91 shows an automatic screw machine. It is so equipped and geared that when a rod of metal, usually about 16 feet long, is placed through the main spindle at B, and the machine started, it continues work unattended until the rod is entirely cut into articles which the machine is at the time set to produce.

The rod is gripped by a small chuck C, with enough of the rod end extending beyond the chuck to be operated upon by the various cutters. Most of the cutters are mounted on a small turret T, the axis of which is horizontal and at right angles to the axis of the spindle. The shaft which carries the turret is mounted on a carriage D which can slide back and forth parallel to the direction of the spindle axis. The whole mechanism is so geared together that the part of the rod extending beyond the chuck is operated on successively by each of the six tools clamped on the turret and revolved into place at the proper time. In this way the accumulated cutting of the several tools on the rod end, each tool doing its particular part of the cutting, shapes the pieces as required. When so shaped, a cutter cuts the piece off the rod end, and it falls into a box below. The rod is then automatically fed in a definite amount for the cutting operations to be repeated.

Fig. 91.   Automatic Screw Cutting Machine.

Fig. 91. - Automatic Screw-Cutting Machine.

The machine has an attachment, not here shown, for cutting a screw driver slot in the head of a screw after it is cut from the rod.