The automatic screw machine, in its design and method of operation, is a highly developed type of turret lathe, its cutting tools being carried in some form of turret. By the term turret, as used in this connection, is understood a revolving, multiple tool-holder, whether rotating on a vertical or on a horizontal axis; and whether consisting of a single casting having the necessary tool-carrying appendages, or of a cylindrical form carrying a series of sliding, tool-carrying spindles. The principles upon which it is designed and constructed, and upon which it operates, are the same.

The automatic screw machine, as originally designed, was intended principally for making small screws and studs; hence it was called a screw machine. The flexibility of its plan, and its adaptability to a large range of operations, encouraged its development along other lines of work. Normally it was adapted to making screws, studs, and similar work from a bar, which was passed through its hollow spindle from the back of the machine, and was pressed forward against a stop carried in one of the tool-holes in the turret whenever the chuck was opened sufficiently to release the bar of stock. The device which fed the bar through was operated by a weight, and was called a wire feed, originally from the fact that screws were made from pieces of straightened wire. The same device, built of sufficient weight and strength, is capable of feeding quite large bars of stock through a machine of many times the capacity thought possible in the early years of the development of this machine. This wire feed device operated automatically, it only being required to introduce a new bar when that in the machine was used up.

The predominant feature in the design of the automatic screw machine, after the use of the turret, is the employment of drum cams, upon which are fixed a series of removable cam members suitable to the piece of work to be made, and by which the automatic movements of the different operative parts of the machine are produced. It is because of the action of these cams that the machine is classed as automatic.

By automatic, we mean a machine in which all of the movements are mechanically made, including the bringing of a new length of work through the chuck, upon which the various operations are made in succession so that the operator has only to keep the cutting tools sharp and to put in another bar of stock when one has been entirely used up. By semi-automatic, we mean a machine in which the rough piece of work is placed in the chuck by the operator, and on which all the various operations-such as drilling, boring, reaming, forming, facing, etc.-are mechanically performed, as well as the rotation of the turret. Thus the machine operating on bar work can readily be made automatic in a strict definition of the term; while if the pieces are small and separate castings, drop forgings, and the like, they must be placed in the chuck by the operator, and the chuck closed, before the automatic work of the machine commences.

There are built, however, machines of this class, in which the castings or drop forgings are placed in a sort of magazine or hopper, whence they pass to the chuck, in which they are gripped ready for the subsequent machining operations, this work being entirely automatic and the only attention required from the operator being that of keeping the magazine full of pieces and the tools sharp and properly adjusted.