CNC Box Joints

Hi All,

I had the opportunity to do a refresh on the new CNC machine last week with Elliot (thanks again), and I’ve been churning through project ideas and YouTube videos since then.

Building drawer boxes has been one item of interest, and I’ve found a few examples of using the Box Creator and Dovetail Creator gadgets in VCarve. The tutorials I’ve found were both curious folks doing trials to see how the joints turned out, and both makers had some level of success. Anyone at Generator used these gadgets before?

I was going to do some trial and error myself this week trying out some different dimensions and tolerances to see what works and what doesn’t. Happy to share back what I find if it’s of interest.


I haven’t got to use the gadgets myself, but I’ve seen enough youtube vids to get me excited. That’s something I’ll be experimenting with too.

From what I’ve seen and based on my limited understanding of the CNCs abilities, I believe box joints are only possible by using fillets to over cut inside corners, meaning the joints will never be as clean and tight as can be done via table saw. For that reason alone I’ll probably do all my box joints on the table after cutting parts to size on the CNC.

I tested out the Box Creator gadget briefly last night. I cut out two simple boxes with 1/4" plywood using an 1/8" end mill. The gadget takes inputs for box dimensions and tab width, as well as tolerances. It outputs a single toolpath based on your selected tool.

I learned you want to ensure that the mill travels fully through the material and into the spoil board or you end up with a lot of clean up and chip out. On the first box I had the depth set to that of the material, which led to those problems. On the second I went .025" through and that was better. For tolerances, I used .005" and the boxes went together snuggly. If I had endless time and material I might mess around with both of these parameters a bit more.

I confirmed Seamus’s statement above, as well as what I’ve seen on various YouTube videos. Unless you can vertically mount your sheet goods, you will end up with fillets in the corners. I doubt this would impact the strength of those joints, so for use cases where you don’t care as much about aesthetics it’s likely not a big issue.

The first box I did with 1/4" joint width and the second with 1/2" joint width. On the smaller joints, the fillets are pretty outsized compared to the joint width, the second they are less noticeable. I’ll try to edit this with some pictures once I get home tonight.

My next steps are to try out some thicker sheet goods. I have some utility boxes I’m looking to make for the rear of my Subaru, and the speed with which you can design and build using this gadget fits for me.

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you should post some images! I’m definitely interested in your outcome with this-