Make it snappy…
Some of the earliest designs I did for ShopBot in the late 1990’s…the work station and the coffee cabinet…used a snap joint that utilized the springy-ness of plywood to hold them together. They were cut as “hooks” that flexed sideways to let you assemble and dis-assemble the pieces without hardware.
That joint worked well if you just wanted to assemble and dis-assemble a couple of times, but after a while the hooks would break. I liked the “idea” of that connection though, so when an architect and ShopBot owner got in touch that was looking for a box for architectural models that his customers could open without any tools, I figured it was time to re-think things. V2 of the snaplok joint was the result.
The big difference is that the joint snaps “front to back” instead of “side to side”, so there is more continuous long grain to keep it from breaking. I was happy with this new connection type, but it was a bit fussy to machine the ramp on the end and it had an inherent weakness…the hooks would peal off after a couple of cycles. You can read about this evolution in this Medium post
A couple of things have made this joint much more useable. The first is the introduction of the Fluting toolpath option in the VCarve design software that I use, which makes cutting the sloped ends much easier. They are just drawn as a series of lines with a start and end depth specified…they are the green lines in this drawing and can be modified to suit your needs:
The other epiphany was that if I drill holes in the ”hook” when the parts were being cut, short pieces of dowels could be inserted to give cross-grain strength and reinforce the hook.
All these mods required a little more time to cut and more post processing work afterwards, but I’m really happy with them and especially the satisfying “snap” when it goes together!
I made a few things to test it out, but the big test was when ShopBot was heading to San Diego for the Vectric User Group this Fall and wanted a video arcade-ish display to show a slideshow. This joint made it easy to assemble on site and dis-assemble at the end of the event…I was pretty please by it.
As with all things, it has its drawbacks. The slots that take up space in your panels, the fingers stick out beyond the face of the panels, and it’s certainly not airtight! But if you can live with these issues and want to give it a try, here’s a sample joint in VCarve v11.5 to play with. My only suggestion is to start by cutting this version and then modify based on how this works out.
