a metalcutting machine for working surfaces of various shapes with a tool known as a broach. Used for working (broaching) internal and external surfaces, broaching machines are divided into those for general use and for special uses. The working motion of such machines is the straight motion of the ram, which holds the broach, or of the item, if the broach is stationary. Broaching machines are produced with either horizontal or vertical placement of the rams, which may number from one to six, and with single or multiple positions (with movable tables for holding several workpieces). A special group—continuous broaching machines—includes chain and rotary models.
The major parameters of broaching machines are the pulling capacity of the ram, which may reach 1 meganewton, and the stroke length of the ram, which may reach 2 m. The cutting speed of general-purpose machines varies from 15 to 20 m/min and in special machines may reach 90 m/min. The cutting speed in continuous machines ranges from 1.5 to 15 m/min. The drive in these machines is usually hydraulic, but high-speed machines use electromechanical drive. Broaching machines are used in mass production and in producing items in large lots. They provide high precision (classes 1–2) and low surface roughness on the worked surfaces (classes 8-10).
Several trends can be seen in the development of broaching machines, including automation in positioning and removing the workpiece, in tool feed to the workpiece, in attaching the tool to the chuck, and in returning the chuck to the starting position. Another trend is to design machines in which the pulling force is coaxial with the broaching force. Such a coaxial arrangement significantly reduces frictional forces on the ram guides, thus increasing precision. Broaching machines are increasingly incorporated into automatic transfer machines.
REFERENCEMetallorezhushchie stanki, 2nd ed., vol. 1. Moscow, 1965.
G. A. LEVIT