How to Program your CNC to cut a Keyway that is wider than your Broach Insert

Have you ever needed to broach a keyway, but then realized that the standard keyway widths offered by CNC Broach Tools won’t work for your keyway width tolerance? This usually isn’t an issue since CNC Broach Tools can create custom width grind inserts and ship them within 10-14 days. But, what if you need it sooner?

Look at the example above: To broach a 3/8″ wide keyway with your 5/16″ broach tool simply offset the tool off center. Program a complete broach cycle on both the left and right side of center. This can be done in any CNC Mill and can also be done in Lathes with Y axis capability. The example above shows our .318” wide insert broaching a .377” wide keyway. The first broach cycle is offset .0295” to the left side of center. The second broach cycle is offset .0295” to the right side of center.

Never exceed the Height of Groove Dimension

Never exceed the max radial depth of the insert when doing this. The radial depth is also known as the Height of Groove (HOG) dimension. The HOG Dimension can be found on our insert dimension page. The example above works perfectly because the radial depth of the 3/8″ keyway is .1875″ and our N8MM (.318″) insert has a max radial depth of .200″.


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