Broaching

Broaching finishes cored holes with or without keys or splines within very close limits. Standard broach design is appropriate. If burnishing lands are incorporated, a very smooth surface results. In some cases broaching is better and cheaper than reaming. Standard broaching machines can be used, or punch or arbor presses can be adapted. Broach sizes should be selected carefully, as zinc alloy that has been stressed sometimes shrinks back after release of the load, this process occasionally taking hours or even days to reach completion.