Yet to be actually cut, and I may abandon this idea, but here are photos of a board a leg extender joint for a parsons table. 

The table I have is 18" tall, but I'd prefer it to be 24" tall to make a more useful side table.  I'd have to be able to remove the legs to cut this on the bottom of them.   Debating on whether to use the same wood or a contrasting wood to emphasis these "feet" and the joint.  Walnut perhaps which I have some of. 

 

I've come up with a similar joint for extending dowels and it got used to good effect on a couple of student projects.  That one is likely already posted here.

 4D

Very cool concept and def a strong looking joint for sure. You can always do a mock up and see if you like it. 

I might have some scraps to prototype it with.  I'd have to glue scraps up to make 2"x2"  block.   Waiting on finding a pickup I want and can afford before restocking my shop with some assorted hardwood. 

4D

Would not want to try this without a CNC.

16 hours ago, kmealy said:

Would not want to try this without a CNC.

I played around with variations that you could cut without a CNC.  If you can imagine sliding the sides together diagonally then a variation that looks the same when glued up could be cut if you don't mind standing the boards up over a router table or table saw dado blade. 

 

My CNC, with the open t-slotted frame, was the one purchase I made that opened up all sorts of possibilities for complex furniture joinery and part creation.  Mounting it on 4 posts with no top under the frame leaves the whole volume from floor to frame for potential use under the spindle.   Most extreme use was hanging a nearly finished piece of cabinetry upside down in the frame to cut a mortise array 4 times for 4 legs to socket into.  Blog post about it:  Bridge supports  

4D

 

 A related version,  for flat boards.  I may have already posted this somewhere as I made the sample while I was still teaching and probably 6 or 7 years ago.  These are fresh photos though.  

Just added it to my blog with more details and a couple more photos:  https://4dfurniture.blogspot.com/2024/07/cnc-cut-end-to-end-finger-joint.html

I've found a use for the square version that started this post.   No use found yet for this version. 

4D

You could do the top version with a RAS in horizontal mode.   If you're feeling lucky.  Or as Dirty Harry said, "...you've got to ask yourself one question: Do I feel lucky? Well, do ya, punk?"

Before I had a CNC or a table saw or lathe or jointer/planer my Craftsman radial arm saw was the king of my shop. It took care of half laps and dados and a few other conventional joints. It also tried to kill me a couple times when I asked it to do the unconventional things. 

Nothing about being lucky involved.  Mostly about being young and dumb.     Had I been lucky I would have succeeded. 

4D

Finally found a good use for the joint that started this thread.  Made a mistake cutting a leg too short on one of my TV tray table iterations. I had 1/2" of extra length to use so I cut this joint 1/2" deep to put the leg back together. 

Second  test fit while still on my CNC.   First test the halves couldn't slide together.  Added a .003" allowance and ran the toolpath again to get this fit.

On  the right leg, 4" down from the top.   You can also see the other oops I repaired where I cut a 2.75"" mortise for a 2" stretcher.  Simply used the same vector to cut a perfect patch, glued it in, then cut the 1.75" mortise where it should be.  Fortunately this point of view is unlikely to occur while using the table normally and "out of sight is out of mind". 

4D 

Yay 4d !!!!!!!

4 hours ago, honesttjohn said:

Yay 4d !!!!!!!

Thanks John.  I've got a box of joint samples. Most of them I made while I taught.  Some inspired by a past student project so I could show new students a potential solution. Some done just to see/test their potential  for connecting wood parts at angles or compound angles, or together end to end.  That second group of samples came in handy very rarely, but having the sample to show always was better than trying to explain to a student how the connection they needed to make could be done.  This sample ended up to be the perfect solution as I didn't have any more maple to cut a new leg from. 

4D

Great and creative save 4D. I really had to look at the picture to see it. Even then, it looks like an incorporated design feature.

8 hours ago, Grandpadave52 said:

Even then, it looks like an incorporated design feature.

If I didn't have enough maple to add back to the too-short leg I'd have likely just used cherry or walnut.  That of course would have made it stand out to draw focus.  While teaching I had a student use my circular version to extend 1.5" diameter oak posts with walnut. That was a design feature for sure.  

4D

Nice!