In order that work may be held rigidly for the performance of hand operations, the machinist uses what is termed a vise. They are made in a great variety of forms and sizes, but all consists essentially of a fixed jaw, a movable jaw, a screw, a nut fastened to the fixed jaw, and a handle by which the screw is turned in the nut and the movable jaw brought into position. The sectional view, Fig. 43, shows these parts clearly and also a device, present in some form in all vises, by which the movable jaw is separated from the fixed jaw when the screw is backed out of the nut. In the machinist's vise, both jaws are made of cast iron with removable faces of cast steel. These may be checkered to provide a firm grip for heavy work, or may be smooth to avoid marking the surface of the plate operated upon. When holding soft metal, even the smooth steel jaws would mar the surface; and in such cases it is customary to use false jaws of brass or Babbitt metal, or to fasten leather or paper directly to the steel jaws. The screw and handle are made from steel and the nut from malleable iron.

Fig. 43. Bench Vise

Fig. 43. Bench Vise.

The common method of fastening a vise to the bench is by means of the fixed base shown in Fig. 43, although a swivel base such as is shown in Fig. 44 is preferable. The vise shown in Fig. 44 also has a swivel jaw, which enables it to hold tapered work securely. This swivel jaw is provided with a locking-pin, which fixes the jaws in a parallel position. The height of the vise from the floor depends somewhat on the class of work to be performed, but a general rule is to have the top of the jaws about 1 1/2 inches below the point of the elbow when standing erect beside the vise.

Fig. 44. Swivel Work Vise

Fig. 44. Swivel Work Vise.