The keyway broaching method is usually used to cut into small metal parts in large volumes and measured in millimeters. While keyholes for locks are shaped from keyway broaching, the process is mostly done to produce pulleys, gears, small wheels, gun components and tools like wrenches, fasteners and bushings.
Keyseaters also make blind spots, which are slots that don’t extend all the way though the whole work-piece, as well as other straight-sided features. The keyhole shape is round with a square cut out at the top. Like all broaching, keyway broaching generates a large amount of excess metal material, which can usually be re-used to form new metal products.
The broaching process is usually done in the same facility that fabricates the product and is used as a post-forming process. If a company does not want to invest the money in keyseater machines, or any other broaching machines, they can always go to a broaching shop to get their products produced in a cost-effective and stress-free manner.
Keyway broached products are generally smaller in size, but there is virtually no limit to the dimensions of the part or product being worked on.
All keyway broaching machines are CNC operated electromechanical machines that are composed of a long, skinny tool that has a series of progressively larger sharp teeth that cut through metal and a ram. The tool, called a broach, moves linearly and uses the series of teeth that are arranged to cut the metal in a specific shape.
Keyway broaching can be done to metals with hardness less than Rockwell 35, but very soft metals like brass, copper and aluminum run into problems as well, including depth drift and a poor finish. The process requires a large amount of lubrication, which is provided by water, oil, a water soluble coolant or tap cutting fluid. In order to cut a keyhole shape, the machinery requires support from a broach horn, which is a fixture that supports the broach in a shared circular hole.
In order to effectively cut a keyhole shape, the keyseater must have a rigid set up, as well as proper alignment of the broach tool, work-piece and ram. The process involves turning the broach so the teeth face the back of the press, let the bushing protrude above the work-piece for support alignment, and centering the broach under the ram at the beginning of the cut.
Keyhole broaching machines also have a guiding system above the work-piece to minimize deflection and increase the cutting tolerances.