# I invented a new joint



## notact (Oct 11, 2021)

Not really. I'm a total n00b at wood working, and I'm not foolish enough to think I'm the first person to do anything. What is this? If I know my terms right, this is like a cross between a sliding dovetail and a loose tenon. Or maybe a long edge butterfly. Seems like this should be a common technique but I can't find any references to it.










This may become my new edge joining technique - it is ridiculously easy to set up and IMO has many advantages over standard T&G I had been doing. I think it can maybe also do things a standard dovetail joint can't. Thoughts?


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## prazbotta (May 20, 2020)

Is the butterfly a spline running the entire length of the two boards it is joining?

I can see the weak point being where the two boards meet in the middle of the butterfly. Other than that, it looks pretty interesting.


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## notact (Oct 11, 2021)

Yes, it is running the full length of the edge. I had the same thought about the weak point. However, I believe the weak point here is no weaker than a tongue & groove of the same dimension as the spline's minimum thickness.

One thing I experimented with today is that reducing the height of this spline stock (relative to the combined height of the dovetail grooves) before "butterflying" it has the effect of drawing the two joined pieces together much more tightly. Very similar to how a drawbore joint works I think.


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## bilyo (May 20, 2015)

Yes. It should be quite strong. However, since most edge joints glued long grain to long grain are stronger than the wood, I think a spline like you show is unnecessary overkill. Most of the time in situations like you illustrate, the purpose of a spline is for alignment, not strength and a straight spline will serve that purpose without the additional complexities of cutting the bowtie shape. Having said that, in situations where the spline would be exposed, the exposed bowtie would make an interesting detail. Sorry to burst your bubble.


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## therealSteveN (Oct 29, 2016)

I believe your potential "weak point" will be determined by the amount you are inserted, and how beefy it is to begin with. Just like a Domino, try a little one on a big slab of wood, and it's unsatisfactory, throw in a big one, or a few big ones, and you are golden.

But like any joint, it will have places it won't shine, and some where it will.


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## Tony1212 (Aug 26, 2013)

> Yes. It should be quite strong. However, since most edge joints glued long grain to long grain are stronger than the wood, I think a spline like you show is unnecessary overkill. Most of the time in situations like you illustrate, the purpose of a spline is for alignment, not strength and a straight spline will serve that purpose without the additional complexities of cutting the bowtie shape. Having said that, in situations where the spline would be exposed, the exposed bowtie would make an interesting detail. Sorry to burst your bubble.
> 
> - bilyo


I agree. I'm not sure what issue this is supposed to address. Edge grain to edge grain glue ups are pretty strong on their own.

OP mentions that they like this method better than the tongue and grove method they previously used. Why were you using T&G in the first place?

Upon re-reading, I realize this may come off as condescending. I don't mean it like that. I am genuinely curious about your thought process. You say you're a newbie to woodworking and sometimes new eyes can teach us oldsters something.


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## Unknowncraftsman (Jun 23, 2013)

Too me it's not a practical joint. 
That might be why it's not listed as a tried a true woodworking joint
Something I've noticed about new guys or girls in this craft . They over complicate things over build or try to build extra strength into pieces. That usually end up with clunky over sized parts that don't allow for expansion and contraction.
That last common theme shiny everything needs to be glossy.
Good Luck


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## bilyo (May 20, 2015)

Notact, please don't be discourage or irritated by the above. Your craftsmanship in putting that joint together is excellent. Keep going and have fun.


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## AlanWS (Aug 28, 2008)

It looks like good practice to make, and that it fits nicely.

I would probably call it a loose or inserted sliding dovetail.

Joints are generally intended to solve a particular purpose. For instance, tongue and groove serves to align boards edge to edge, and sometimes to make the joint look closed even when boards shrink in width. Glue is sufficient to hold edges together, so a glued tongue and groove joint just serves to align.

Sliding dovetails do provide pull out strength, and so tend to have the tail portion with grain running perpendicular-so it's strong in the pull out direction. The sliding nature of the joint lets each portion expand and contract in width (but not length) with changing humidity, so the mostly unglued joint can remain closed and strong.

It's good you're thinking about joints. You might want to go over a list of joints and ask yourself what problems each can solve. That helps to understand where each is useful, and whether there is a joint that would be useful to add.

Of course appearance is a use as well, and you can design your joints to look interesting. Yours does.


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## LesB (Dec 21, 2008)

As already said that is great craftsmanship.
However the grain orientation which is the same as the boards being joines it liable to induce a split in the butterfly where the blue line is in the image here.
The grain of the butterfly should run in the direction of the red lines.


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## jonah (May 15, 2009)

What's the advantage of this over a mortise and tenon joint again?

It's not stronger.
It's not easier to make.
It *may* look better if it's a through mortise and tenon.

Seems like a solution searching for a problem, personally.


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## pottz (Sep 15, 2015)

id agree with the majority,why ? why waste the time for something that gives no improvement.


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## bondogaposis (Dec 18, 2011)

It is an unnecessary joint unless it is meant to slide for some purpose.


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## Ocelot (Mar 6, 2011)

I think it is interesting. The grain being alligned the same as the joined boards means that it should expand and contract together with them.

There is a saying,

"For the novice there are many possibilities, but for the expert there are only a few."

I'm still an old novice.

-Paul


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## Lazyman (Aug 8, 2014)

To me the purpose of such a joint would be that you do not need glue and that you could disassemble it (assuming that wood movement doesn't cause it to lock up). It is basically a sliding dovetail that uses a spline instead of a tongue and groove approach.


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## robscastle (May 13, 2012)

I think you joint is OK.
I don't think I would use any glue


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## pottz (Sep 15, 2015)

> I think you joint is OK.
> I don t think I would use any glue
> 
> 
> ...


how many times has the duck told you you need to trim your nails rob ?>


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## nickbatz (Mar 7, 2018)

> I think you joint is OK.
> I don t think I would use any glue
> 
> 
> ...


You beat me to it. 

I was going to mention the Camberwell Carrot, something only a fan of Withnail and I (late '80s) would appreciate.


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## controlfreak (Jun 29, 2019)

I get the feeling that if you applied glue to that and tried to slide it in, it would swell and seize before you got it home.

It does look nice though.


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## bandit571 (Jan 20, 2011)

That sort of joint has been used before…..

Dinning Room tables, with 2 sets of 3 bars that slide to open the table to accept the extra leaves to make the table longer. Table that my folks had, used that sort of system…to allow up to 3 leaves to be added to the table.

As for using glue…only the last 2" in the sockets, and the last 2" on the Butterfly….right before you drive it home. Nothing to it.


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## notact (Oct 11, 2021)

The reason I did this is because I am fascinated by the idea of joints that self-align and provide strength mechanically, even in the absence of glue. I would still glue anything assembled this way. The joint not only ensures alignment, but it is an insurance policy in case the glue fails for any reason. Also I had not worked with a dovetail bit before and wanted to experiment.

Several have pointed out complexity - IMO this is super easy, especially compared to the traditional sliding dovetail where you have to make two different cuts with two different fence positions, and I believe you have to "sneak up" on the tail cut (disclaimer: have not done one). Basically the fence is positioned such that looking down it, the cut begins at the corner of the fence and table surface. A piece the same width of the bit and 2x the height of the bit (convenient 3/8" x 3/4" here) is run through four times. You guys have probably already figured that out. This tenon stock could be made in bulk in advance, since it pairs with the bit that cut it. Later, all you would need is to ensure the bit is the right height, pick your fence position, and all mating pieces can have the same groove cut into them.

I'm going to try a few variations of this in a test project, and see what works and what doesn't. I also think it looks interesting, so the ones that are exposed I will make "loud & proud".


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## Lazyman (Aug 8, 2014)

This is an example of what Bandit was talking about.


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## bilyo (May 20, 2015)

I'm not able to read minds, of course, but I think most of the comments above are based on need and efficiency of construction. But, you are having fun experimenting and that is how you discover better ways of doing things. Keep up the good work.


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## robscastle (May 13, 2012)

Experimenting is good, however I don't think I would put glue on it and slide it in,...I might never get it out again!

Hey its almost Christmas and its all good cheer!

ha ha ha ha ha ha groan gasp and hang on


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## SMP (Aug 29, 2018)

That is called the "time wasting complex weak loose tenon joint."
I'd much rather use a full width super simple M&T joint. But I'll be curious if Madmark sees this and tries it with his signature dog bone joinery


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## Sylvain (Jul 23, 2011)

I see two uses:
- no glue assembly (see below);
- sliding pieces as pointed to by Bondogaposis, Bandit and Lazyman.

- If you like no glue joints, visit the site 
https://thecarpentryway.blog/
Unfortunately, the author, Chris Hall, died from a cancer in April 2020.
So look for post older than that.
the serie "dark chocolate and sponge cake" 
in particular the 5 last pictures of this post:
https://thecarpentryway.blog/2019/03/dark-chocolate-and-sponge-cake-20/


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## DS (Oct 10, 2011)

I've always wondered who invented the French double sliding dovetail joint.
And now I know.

Thanks!
(Are you actually French? Or is that just what you decided to call it?)


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## robscastle (May 13, 2012)

here is an example of the joint at work
Humour!!


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## Sylvain (Jul 23, 2011)

In the "carpentry way" link above, Chris Hall used the principle more clearly shown here:
https://www.finewoodworking.com/1997/04/01/housed-sliding-dovetails 
except he used bow-tie keys.

One can buy keys here:
https://hoffmann-usa.com/search.php?search_query=key&section=product
They have 12" various wood ones, the plastic ones are by packs of 1000!


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