3-way corner joint alternative

[4DThinker]

When I'm bored I get my sketchpad out and this time I filled a few pages with options for how a 3-way corner joint could be made. This is a test piece I cut with my CNC to see if a simple change from two miter cuts on each piece to convex/concave curved cuts would actually work.   The scrap boards weren't perfectly square which is why the inside corners are offset a bit.  Obviously the cuts went together fine, but there is a hidden void in the core of this corner which I didn't foresee.  

I've got a few more alternatives to test and more scraps to play with so I'll see what shows up in my CNC room tomorrow. 

4D

[Masonsailor]

Interesting idea. What are the dimensions of the pieces ?

Paul

[4DThinker]

1+7/16 x 1+7/16 x 6" long. A scrap of old pine I had in my garage. 

Of course this can't be done with a miter saw, but it would be easy to scale up.   Had a thought this morning about injecting the void with a acrylic resin but I'd have to order some to try that.  

4D

[KevTN]

I like that concept! I am still trying to teach myself to think in 3D 

[4DThinker]

8 hours ago, KevTN said:

I like that concept! I am still trying to teach myself to think in 3D 

3D is not too hard, at least for me as I live in a 3D world. Visualizing how simple 3D parts can spin around and connect to make a more complex 3D part gets a bit more challenging.  Found myself to be pretty good at that after helping college kids make their furniture designs for the last  40+ years.  Dynamic 4D designs that when assembled and can reconfigure over time are the real brain ticklers.   Don't ask about 5D designs as I'm not positive that parallel dimensions exists. 

4D

[4DThinker]

Another variation I've cut out and glued up.  Waiting for the glue to dry but here is an image of what the CNC cut for each piece. 

Calling it a stepped 3-way miter corner joint. Pocket cuts include a roughing cut to remove most of the sloped face, and pocket cuts for the flat surfaces and bottom removed area.  Moulding toolpaths with a 1/8" ball nose bit to smooth the sloped surfaces, and round over the two edges that eventually mate with the two matching pieces.  A little chisel work was needed to follow the rounded edges into the corners where the bit couldn't reach.  Images of the assembled joint likely tomorrow. 

4D

[4DThinker]

Glued up.  A little tear-out from the CNC pocket cuts.  Was easy to clamp up given the flat faces on each part. 

 

This one has no voids in the joint.  It could also be stretched for a corner with a square leg and rectangular stretchers.  More glue surface than simple miter cuts on all three parts. You could also pin the joint with dowels through each side into the end grain of the neighboring piece.  

4D

[KevTN]

Nice!