Pot Broaching: The Lesser Known Method of External Broaching
There are numerous ways to categorize broaching methods. One popular categorization method used separates broaching methods between internal broaching and surface broaching. Internal broaching is performed on the inside of the workpiece whereas surface broaching is preformed on the external surface. A less common method of external broaching is pot broaching. This involves cutting splines and shapes into the outer diameter of a workpiece, most commonly used for gears. It does so by altering the outside edges of the part.
This method is often considered the opposite of an internal broach, which forms a hole in the workpiece by pushing the tool all the way through. Gear hobbing is often preferred over pot broaching because pot broaching can only be used on cylindrically shaped workpieces. Pot broaching was named for the hollow fixture that is used to hold the broaching tools. The fixtures are basically a pot-like casing with a hole in the middle where the broach would go. Multiple broaches can be held over the entire length.
Another name for pot broaching is ring broaching. Normally done on a vertical broaching machine, the process of ring broaching involves pushing or pulling one or multiple workpieces through the bore of a pot broach subholder. There are three basic types of pot broaching; ring, stick and a combination of the two. Sticks and ring broaches are both individually formed broach inserts used by broaching machines. All three pot broaching methods have internal cutting tooth configurations.