Broach

A broach is a series of chisel points mounted on one piece of steel. A broach is typically used to enlarge a circular hole into a larger noncircular shape such as a square or other desired shape. Another typical use of a broach is to cut a square keyway on objects such as gears, pulleys etc. The amount of material removed by each broach tooth (or chisel) varies with the material being cut. A broach designed to cut steel might remove 0.0025 thousanths of an inch, while a broach designed to cut brass might remove as much as 0.004 thousandths of an inch. The succession of chisels removes the total amount of material required. A broach might be designed to be pushed through an existing hole, or, alternatively to be pulled through the hole. Broaching machines are designed to either push or pull a broach.