In this post we’ll see how to make an impossible dovetail joint. Well, actually we’ll see how to make a curved dovetail joint. My idea is to turn one piece towards the other so both parts fit together. I will make both parts of this dovetail joint in the head of two square section strips. And I have to make a dovetail jig to route each part. When I fit both parts together they will look almost like the impossible dovetail joint. Almost like it.
I am going to make this joint on the head of two 6,5cm square section wooden slats. And to do it I need to improvise a simple woodworking guide for milling circles in the wood with the tabletop milling machine.
So, the first thing I had to make is a plywood box into which the wooden strips will fit perfectly. And in a corner of that box I put a nail tip that serves as a pivot pin, to route the workpieces while moving the plywood box describing an arc of a circle.
The guide to cut in a circle It is completed with a plywood board fastened with sergeants on the milling table. In this board there is a groove, shaped like the bur that is used to mill dovetail falls on the inside of the surface of the board.
Thus, I insert the tip of the nail that serves as a pivot pin into position on that board, I press the plywood box together with the workpiece against the board, and I turn both to route a quarter circle in the workpiece.
Then I move the board between the two stops that I have clamped in the router table fence.
And I do a second routing. Thus, routing twice a quarter of a circle in the head of the strips, I have the sockets between the tails in which the tails of the other workpiece will enter later.
And now, with the help of that part that has the sockets already routed, I have to adjust the position of the jig on the router table, to route the tails in the other workpiece. It is best to start with tails wider than necessary, and then gradually adjust them until the impossible dovetail joint fits perfectly.
Although the truth is, as you can see in the video, I have to cut some parts with the hand saw (that corner that I point with my finger, is better to cut it with a hand saw). And it also takes a little work with the sandpaper so that the pieces can fit together well. And now, if I apply some wax, the tails of this impossible dovetail joint can slide in the sockets smoothly.
Adjusting both parts so that the dovetail joint fits well takes your work and time, and you get a joinery union Perfect is going to be almost as impossible as these unions. But surely we can get a decent result. Anyway, I think it is a good practice to improve our skills, and our patience, when it comes to woodworking. And if you like these wooden joints, see how mill semi-hidden dovetail joints, to make drawers with the milling table.