Cutting keyholes in plaques

Can someone give me a good procedure for cutting keyhole slots in the back of plaques. (I have a keyhole bit)

Check this out @Zoomer. It’s a bit protracted but worth the time. He uses Vcarve as the CAD package but there seems to be no reason why it wouldn’t work with any other toolpath creators including Carbon Create. Determining the CNCs entry point might require a bit of experimentation in other applications though. Good luck.

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I cut keyholes into the back of my walnut and oak cribbage boards on my Nomad. I use an 1/8" flat end mill to pocket out everything but the undercut to full depth. Then I switch tools to the keyhole bit and run one very slow pass to finish the keyhole. I use Fusion 360 to create the tool paths and can upload the settings tomorrow if you’re interested.

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If you don’t mind using Easel from Inventables, there’s a great premade tool to generate Keyholes.

It should be one path (a rectangle) with two different toolpaths as @Remmy noted:

  • first uses a narrow endmill to actually pocket to the full depth
  • second uses the keyhole bit, starting at one end and doing a pocket cut which has a starting depth equal to the desired thickness of the support material at the back of the keyhole, and a depth equal to that thickness plus the height the keyhole cutter cuts and the depth per pass set to some larger number so as to get it done in one pass.

Do a test cut first — orientation will depend on where the path begins and its direction — might have to rotate 180 degrees.

Maybe I’m the only one who thinks this way, but a CNC is the wrong tool for the job. You just mount the bit in a standard plunge router, plunge it into the wood and move it an inch or so. Clamp a piece of wood to the plaque for a straight edge if you need a guide. I’ve used a keyhole bit in a drill press before…not the best but for an operation that takes a few moments, it worked.


I have a “pecking” version for Fusion 360 here if anyone wants to add to their keyhole options. I like that I can add them to specific locations on a model and know that if I’m using more than one they’ll be lined up and exactly the same.
I also think writing the keyhole slot gcode by hand is a great way to get into understanding how that all works.

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