Broaching is a process for steadily removing material to create a positive or negative feature in a workpiece. In this sense, broaching is similar to milling or drilling, but it is different in the sense that it is intended to happen in one pass with one tool, and is often used to create non-circular features. This is the main advantage of broaching – it is a processĀ that can quickly and (when done properly) precisely produce a complex feature for production. There are two different ways to categorize broaches: internal and surface, and rotary or linear.

Internal broaches are meant for expanding a pilot hole to the desired geometry of the broach, whereas a surface broach is used to create a feature on the outside of a part.

Linear broaches use a long rod with progressively deeper teeth to progressively make many cuts in the material in one pass. Linear broaches begin with roughing teeth, and end with precise teeth that match the shape of the final feature at the end.

Rotary broaches match the shape of the desired feature, but sit at a roughly 1 degree angle off-axis form the axis of rotation for the tool. This off-axis rotation causes each of the edges of the rotary broach to slightly oscillate back and forth. Since those edges have a small relief behind them, the back and forth motion takes small cuts out of the material, creating the shape of the broach. These rotary broaches can be very simple, but can also leave a slight spiral in the shape of the cut.




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