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The impossible joint

labolle's picture

The impossible joint (post #158776)


Here's an adaptation of a double twisted sliding dovetail I came up with.

Has anyone else tried something like this or come up with other variations of the Double-twisted-dovetail?

birchwoodguy's picture

twisted dove (post #158776, reply #1 of 20)

I have seen this joint before, in fine woodworking (long long time ago) an English woodworker was learning the joint from someone or from reading about it, he built a bench using Yew and had a heck of a time with it as I recall.

I have my own version that is really impossible, the joint is made of dovetails that are pitched at 8degrees in two planes. Yep that is what I said, two planes.  The finished joint has the dovetail look on both finished exposed sides of the outside corner.  (ie no pins, just tails on both pieces) And no I am not going to give up my secret as to how I make it.  It is a puzzle that is for sure.



zgmc's picture

My dovetails are so (post #158776, reply #2 of 20)

My dovetails are so complicated that they can only be interpreted in the ninth dimension!

RalphBarker's picture

LOL (post #158776, reply #3 of 20)


BruceS's picture

Labyriynth (post #158776, reply #4 of 20)

Good Lord, My eyes crossed checking out the photo. That guy would never come apart. Very cool joint, nice job.

Work Safe,  Count to 10 when your done for the day !!

Bruce S. 


bones's picture

wow (post #158776, reply #5 of 20)

I look at that joint and see a VT (Va Tech) Go HOKIES!

...For that old machine lovers:

SgianDubh's picture

Another version (post #158776, reply #6 of 20)

Here is a link to another version of the joint labolle in which I describe and illustrate marking out and execution. I've used the joint a few times in furniture I've designed and made, but it is very labour intensive and, therefore, rather expensive to produce and pass on to the customer. Slainte.

labolle's picture

Great article. (post #158776, reply #7 of 20)


That's a great article.  I read through it as I was trying to figure out my first double twisted joint.   Having just re-read it again, I have to say it is a great piece of work.

Have you managed to make a box with the double twisted at all four corners yet?


SgianDubh's picture

"Have you managed to make a (post #158776, reply #8 of 20)

"Have you managed to make a box with the double twisted at all four corners yet?"

I haven't LaBolle. The challenge hasn't excited me enough to try is part of the reason, and I've always had more pressing issues to deal with since I wrote that short article several years ago: I guess it's ten or twelve years ago that I wrote that.

However, I seem to recall reading on a woodworking forum somewhere-- I can't recall which one-- that someone has done it, so it looks like it is possible. I think there were probably photographs of the box as well, which would make sense as visual evidence would be useful. Slainte.

labolle's picture

That was me. (post #158776, reply #9 of 20)

That was me that made the box and posted the pics.


 I'm still messing around with the joint and trying to come up with interesting variations.  For me woodworking is just a hobby and for some reason, to my wife's chagrin, I'm drawn to the challenging much more than the practical.


If you ever want to give the box a try, you put together two L shaped pieces and then slide them together at a 45 degree angle drawing the two completed corners in towards each other and the other two corners join together completing the box.


For anyone else wanting to give this joint a try, I have no secrets to keep and am happy to share.  To lay it out all I need is a sliding t-square set tightly at a moderate angle, a good sharp marking knife, a comfortable place to sit, and a bit of quiet time.  Make sure the t-square  won't slip or change angle as  you will use that t-square many times per joint.  I don't use math to set it to a magic angle.  I have no idea if my square was set to 7, 8, or 9 degrees.  I just do it by eye.  As far as the width of the pins or spacing between them, again I do it by eye.   Look carefully and you should be able to figure out how the angles intersect from the face of the joint on across the top.  Again, I use the same t-square set at the same angle all the way.  The hardest part is transferring the angle from one board to another.  Actually, it's not so much "hard" as very exacting.  The whole joint is really.  You must use the sliding t-square to lay the lines at a precisely consistent angle.  The cutting, as well, must be spot on.  I have not found any way to fudge or repair a mis-cut line.  If you lay out every line consistently and cut them each precisely the joint will work.  

joinerswork's picture

Hello Richard, It's good to (post #158776, reply #10 of 20)

Hello Richard,

It's good to "see" you.  How is your lady doinbg?  I hope her health issues are satisfactorily resolved.


SgianDubh's picture

Thanks for asking Ray. I have (post #158776, reply #11 of 20)

Thanks for asking Ray. I have been very quiet over the last couple of months, not that I've been an especially prolific poster since the switch over to this latest clunky, user unfriendly forum format about a year ago. I've been rather preoccupied with her illness and the attendant things the nearest relative has to deal with to bother much with woodworking forums and the like.

My wife is still not well, and has been in hospital since early September. It took a month to come up with a diagnosis, which in the end turned out to be a rare form of meningitis. If you are curious, the exact diagnosis is idiopathic hypertrophic pachymeningitis: yes, it just rolls of the tongue doesn't it! Apparently there are less than seventy documented cases of that exact condition in the world, ever, or so the head doctor in the team treating her informed me. It was described to me in simple terms as the auto-immune system attacking the body, in this case, causing inflammation in the brain and meninges leading to (in my wife's case) pronounced irrationality, off-the-wall emotions, lack of logic, etc.

Anyway, there it is; there's treatment being administered and she is  monitored for signs of improvement. I think it's possible some positive developments have emerged, but only in the last few days. I can only hope treatment does lead to a marked improvement, or perhaps even full recovery given time, and maybe a bit of luck. Again, thanks for asking-- I appreciate the kind thought. Slainte.

RalphBarker's picture

thanks (post #158776, reply #13 of 20)

Thanks for the update, Richard. You and your lady fair remain in my thoughts and prayers.

SgianDubh's picture

Thanks LaBolle and Ralph. (post #158776, reply #14 of 20)

Thanks Labolle and Ralph. We'd better end the diversion about my wife's illness at this point for fear of of hijacking LaBolle's original topic any more. Slainte.

joinerswork's picture

Aye well, (post #158776, reply #15 of 20)

Aye well, Richard,

Meningitis the little I've heard of it is a serious thing in its most ordinary manifestation.  I wish your lady all the best in her struggle with her malady, and hope that modern medical knowledge will provide the cure.

The longer I live, the more I am convinced that life is a crapshoot --and that the longer one lives, the longer the odds of an uneventful outcome.  Just today, they buried one of my late son's friends- he rests almost in  sight of my son's resting place in Arlington cemetery- his sudden death left behind a loving wife and two small children.  And yet, here am I still, having raised my family and so done my duty, genetically speaking.  How does one account for that?

And, yup, I guess this thread is totally hijacked.


Eef's picture

touches me deeply everytime (post #158776, reply #16 of 20)

touches me deeply everytime you talk of your boy...


labolle's picture

Best wishes, (post #158776, reply #12 of 20)


I wish you all the best and your wife a speedy recovery.


I'm a bit concerned about my wife now, and think I may need to schedule her for a complete checkup as those symptoms seems to fit her to a T.

; )

labolle's picture

The ultimate double twisted box = six sided. Done. (post #158776, reply #17 of 20)



I thought you might find this one interesting.

SgianDubh's picture

It is labolle. I wonder how (post #158776, reply #18 of 20)

It is labolle. I wonder how long he spent trying to work out how to do. It's also interesting because he seems to have managed to cut joints (fingers or tails) in the weak short grain on the edge of the wood, and put it all together without the tails (fingers[?]) shearing off during assembly. Slainte.

labolle's picture

Richard, (post #158776, reply #20 of 20)

In the discussion he did mention something about trying to sell a jig to make them.   Doing them with a jig kinda defeats the purpose.  It's like that router jig that cuts out teddybear shaped dovetails.  Interesting to look at, for about 3 seconds, but then?  Eh.   Jig cut dovetails bore me.

labolle's picture

deleted comment (post #158776, reply #19 of 20)

Want to delete this, not edit it.