To remove unwanted metal in workpieces, many companies resort to broaching. To actually remove the metal, a toothed tool called a broach is used. Depending on the machine, the broach is pushed or pulled across the workpiece. The broach removes a small amount of material every time. In order to ensure a smooth-finished product, the teeth of the broach are progressively longer down the length of the tool. This creates chips in the material that vary in size. A variety of surfaces can be machined with broaching including internal and external surfaces.
Broaching machines are also used for cutting grooves into a gear’s spline shaft. These are used to even out the rotation speed of a companion piece through a series of ridges on a driveshaft. Spline shafts are found on a number of applications including bikes. Only external broaching is used for this process. A common shape made with internal broaching is a keyway. A keyway or keyseat is axially located in a shaft or hub. Normally an arbor press is used to cut this shape into the metal. The cut will come through the bottom of the piece out through the top. The actual cut happens on the down stroke.
So what is the advantage of using broaching or spline cutting services? Well, it allows high production levels and creates close tolerances. CNC grinders fabricate the best broaches with low teeth tolerances. These methods also create high quality surface finishes. Broaches have a longer life span than other tools due to the fact they only remove small amounts of material at a time. Manufacturing costs also remain low in the long run, because low-skilled workers can operate the machines for most techniques. However, specialized methods such as blind broaching do require experienced broachers.