Internal broaching is one of the two potential categories of broaching. The process involves pushing a broach completely through a workpiece, whereas surface broaching produces the hole on the surface of the piece. Other possible ways to categorize broaching methods include its purpose, the motion the machine makes, the construction of the broach and the function. The two main broaching machines used in the broaching process are horizontal and vertical broaching machines. Vertical machines are normally used for surface broaching whereas horizontal broaching machines are favored for the internal broaching process.
The internal broaching process is normally automated with a CNC machine. This allows the productions of holes in metal parts and protects to run efficiently and at a fast pace. Depending on the piece and desired shape of cut, different broaches are utilized. There are several different kinds of internal broaches. The most common type is solid broaches. These are broaches made from one solid piece of metal.
Shell broaches are a more expensive version of a solid broach and are used in processes that wear broaches out more quickly. Where the two broaches differ, is shell broaches have an arbor that runs through a hole in the center. This saves coasts overall because the shell broach does not have to be replaced as often. For larger broaching applications, modular broaches are used. This type of broach features a multi-piece construction similar to shell broaches. It’s more flexible than a solid broach and is cheap to produce and re-sharpen.
For cutting thin-walled workpieces, cut-and-recut broaches are used. However, these broaches do have a tendency to expand during cutting and then shrink. A concentricity broach ensures precise concentricity by cutting both minor diameter and the spline form. It’s used for special kinds of spline cutting. Lastly the keyway broach is used for keyway cutting. I touched upon the subject in a previous blog, but a horn is used to support the keyway broach. It helps guide the broach to the proper location on the workpiece.