Saturday 29 July 2017

Keyholes - episode 156

It's time to have a peek into keyholes.
They are very useful when it comes to a method of hanging projects on the wall but there are more useful than that. The slots we use for out holddowns on the CNC table are nothing more that Keyhole slots that run the entire length of the table. Used properly these slots can work well but ther do not have the strength of and Aluminum Extrusion but on a small machine they could work OK. I used a Keyhole cutter to cut slots in my router table for fence adjustments and they work very well.

Back to Keyholes for mounting projects to walls.
Not many CAM software packages can create the required toolpaths but VCarve Pro and Aspire can by the use of Gadgets. There is a gadget for Keyholes and it created the necessary toolpaths for cut them. Keyhole toolpaths are different in that the require the cutter to plunge the full depth into the material and them move along cutting a slot under the surface. A small slot is cut by the shank of the cutter. It then needs to reverse back to the original entry point and exit using the hole.

 Click to View video


Keyhole cutters come in varing sizes and designs but the most common is the basic L or T shaped cutter but this by no means the only shapes they come in.


They all have a couple of things in  common. A large blade at the bottom and narrower blades above it to allow it to undercut the surface. In normal theses cutters are put under a lot of stress because they cannot clear the cut material so take it slowly.
While the Bottom blade seem to come in standard 3/8" and 1/2" the upper blades seem to come in several sizes. 
3/8" Lower with 3/16" upper or 1/4" upper
1/2" Lower with 5/16" upper or 1/4" upper
There are also metric versions of these cutters of very similar size so choose carefully what you buy. As with all cutters the price varies considerably froma couple of dollars to $50 or more. Given how often you are likey to use a keyhole cutter I would tend to get the cheaper one ans wouild probably be lucky to blunt it and remember those cutters can be sharpened easily.
The one thing you must watch out for is the maximum depth of cut which is determined by the overall length of the cuttinb blade. This will be the large and small bales combined height. Do not exceed this or you will break the cutter.

I have created some Gcode to use for the cutting of keyholes to hang projects on the wall. Please read the READ ME fole included in the zip files below to make sure you understand the requirements and the risk of using unknown Gcode.

Imperial Keyhole

Metric Keyhole



 Where to purchase cutters

These types of cutters are available from many suppliers so pick the supplier that works best for you.

Please note that by using the link provided to visit the Ebay site I receive a small commission on any purchase you make at no extra cost to you. The link will provide you with search results for Keyhole cutters so shop around and find the best deal for you. If you do use the link then thank you for supporting my channel and remember it costs you nothing.


 Keyhole Cutters

Many thanks for visiting and I will catch you on the next one.



  1. Thanks peter, I was wonder how to do this! Good answer.

  2. I just love all of your videos. Thanks for the files it is greatly appreciated

  3. Thanks Wayne.
    Hope you find the files useful.

  4. How Would I use these with my CNC Piranha by Nextwave?

  5. Hi Peter

    Many thanks for this, I want to try the files but I cant work out how to get them from the text file which I can view and into UCCNC for a test run. Cant copy the text and paste it, had a quick google to no avail. I am probably doing something dumb...


  6. Update to the previous post. I was doing something dumb...I was trying to copy the txt file directly from dropbox. When i actually downloaded them they worked in the normal way through the load file button in UCCNC. Tried one on my demo copy at home so Should work when I get to the workshop next where my machine lives.
    Many thanks again, stuff like this is so helpful to CNC beginners, I only have vcarve desktop so no gadgets.


    1. Glad you got it sorted Ollie