Mortise and Tenon - Fox Wedged (aka Jigoku-kusabi)

Fox Wedged Mortise and Tenon Joint
Try your hand at this joint, but be prepared to destroy it to see how well you did!
The Fox Wedged mortise and tenon joint combines the stealth of the stub mortise and tenon, with a large degree of the strength of the wedged mortice and tenon. However the strength very much dependent on the correct wedge being prepared, so that the tenon ends are tight against the mortise ends.
Watch me prepare this joint, from the starting point of a well fitted stub mortise and tenon (a video for which is earlier in this series). Then watch as I saw the thing in half to reveal how it's gone together.
Thanks to Shawn, who tells me that in Japan this is called Jigoku-kusabi.

[@dougieF747]

This joint is not for the faint of heart. Well done!

[@mitchwoodwork]

Thanks Douglas, I was relieved when I cut it open and saw how well it has worked! Happy woodworking, Mitch

[@jkaguiar]

I loved this video. you are extremely instructive. thank you for your patience to detail as well the steps.

[@mitchwoodwork]

jkaguiar My pleasure

[@CMRWoodworks]

Interesting joint. It was very interesting seeing it cut in half. It may be quite some time before I attempt it.

[@mitchwoodwork]

Go on, give it a go! It's fun to practice joints that you have to cut apart to evaluate. Happy woodworking, Mitch

[@missionron]

I plan to use this joint on a largeTeak estate planter. Thank you for taking the time and effort to make this video!

[@mitchwoodwork]

Swedish Holmberg My pleasure. Try a full size practice joint first, then saw it in half to check all's well with your measurements - be a shame to build the planter and find the joints fail when you use it. That's the trouble with this joint, you can't check it without destroying it! Good luck, and please email a photo when you're done. Mitch

[@hutts57]

Awesome! Love these videos you've done on Japanese style joints.

[@mitchwoodwork]

Cheers! More of those Japanese joints to come

[@xkabedaruhe2956]

Hi Mitch, I really like your joint series! Thanks for sharing!

[@mitchwoodwork]

Thank you, I really appreciate hearing that. Happy woodworking, Mitch

[@scottydog1313]

Great video. This makes me want to try this. I'm not very good at doing using hand tools, I've always used power tools, but this looks like its doable for someone of my skill level.

[@mitchwoodwork]

Thanks Scott. Try it - I hope I explained it all okay!

[@kgrafphoto]

Well done! This is a good joint to keep in your arsenal when the extra tension strength is needed.

[@mitchwoodwork]

I do wonder whether modern adhesives make this redundant in most instances, but better to be safe than sorry. Happy woodworking, Mitch

[@weldabar]

Great. I've not seen a lot of people get this right. It looks like a fun joint to make. I'll try soon.

[@arnold7156]

wow mitch, I see where your engineering background comes in. beautiful joint.

[@mitchwoodwork]

+Arnold Espenberg Thanks Arnold

[@nuttiBONG]

Here it is, the joint that i thaught i invented myself when making chairs without visible pins to hold the joints together. I called it the fishbait because it looks like a fish mouth if you only use one pin on a round tenon :)

[@mitchwoodwork]

Like so many 'new innovations' in woodworking these days, there's a good chance it will have been invented ages ago, possibly forgotten and reinvented many times over! Nice for you to know that you came up with it independently though. Happy woodworking, Mitch

Very beautiful craftsmanship, indeed! But I wonder if all this extra effort actually pays off in terms of strength of the finished piece, considering modern carpenter's glues are stronger than wood. With the simple mortise and tenon, if the joint is going to fail at all, I expect it will be with the wood cracking where the tenon begins, not the tenon coming loose from the mortise. And with this fox wedged joint, the two cuts on the tenon could perhaps make it more prone to cracking. It's just a thought, I'm not really sure...

[@mitchwoodwork]

Thanks for these great points. Perhaps it is over kill - nice hand tool skills practice all the same. If you were making a number of these joints, you would prepare a jig to cut wedges, and an angle block to chop the ends of the mortises, both quickly and accurately. Once prepared, the joints would barely take any longer than standard stub mortise and tenons. I would take claims about modern glue strength with a pinch of salt; the fact that they are modern suggests that there is no long term strength data. If the tenon grain is parallel to the cuts made for the wedges, then they shouldn't weaken it. Cheers, Mitch

[@sweedish9184]

This is amazing, basically a backward wedged mortise and tenon

[@mitchwoodwork]

Cheers, glad you liked it. Happy woodworking, Mitch

[@josecallard]

Nice

[@Bennetts74]

Great job

[@mitchwoodwork]

Thanks. Happy Woodworking

[@pamvrosiadis]

very intresting video! thanks!

[@mitchwoodwork]

Panos Amvrosiadis Thank you. Really appreciate any comments, but especially positive ones like that! Mitch

first video I've seen of you and sub'd mate! I know these joints are pretty tricky if you don't get it right first time and you made it look easy and explained everything perfect!

[@mitchwoodwork]

Thanks Jay. I found just drawing it all out to be the best way of learning how to size the slots and wedges. Woods that will give a little are a distinct advantage, but there is no substitute for working things out properly

[@jasonb4350]

I live all the different joints you do I also enjoy making Japanese joinery I believe this joint is only used in the case were there are no fasteners available like nails or screws or even glue and the two holes made for the wedges does create a week point

[@mitchwoodwork]

Cheers. I believe the holes prevent the wood splitting as the wedges seat fully, especially if they are made a little too big.

[@jasonb4350]

Mitch Peacock - WOmadeOD I agree but it takes away from the overall strength

[@mitchwoodwork]

Yep. I guess if strength rather than aesthetic is required then using a straight grained tenon and no relief holes would do the trick. Any split wouldn't significantly weaken things. I came up with an alternative to this joint, which uses similar principles. I should make a video on that and see if anyone else has ever tried it.

[@lilymoreno6003]

this joint is also used extensively if you have made a mistake and have a little to loose of a fit

[@mitchwoodwork]

I guess if you under cut the ends by mistake. My preference would be to shim the ends or cheeks of the tenon and refit. Cheers

[@Tome4kkkk]

What resources would you recommend on Japanese joinery >basics

[@mitchwoodwork]

Practice mortise and tenon, and dovetail joints, as these skills will be invaluable when getting into Japanese joints.

[@Tome4kkkk]

Excuse me for being a stubborn spanner ;) What would be the first two Japanese joints I should explore in your opinion?

[@Diozark]

Great Video, Have you tried reversing the wedge design ? If the tenon is made oversized, and then cut the relief, the ( built in wedges will be pushed in towards the center of the tenon, vs a seperate wedge pushing the edges of the tenon outward. In other words cut the tenon in the shape of your dotted lines ( dovetail ) then compress to push into the mortise ?

[@mitchwoodwork]

No, not tried that. Better for dry joints I would imagine, in case the tenon doesn't expand fully before the glue grabs it. Must try a few and carry out some investigations. Thanks for the idea!

[@MdeLongpre]

Do you think this would work connecting a tabletop to a couple legs, using no glue. I am designing a table with zero glue, nails, screws, etc.

[@mitchwoodwork]

+MdeLongpre It could, but consider the expansion and contraction of the table top. You may wish to experiment with the wedge angle and surface preparation too, since with no glue the wedge might want to slip out. I can think of more practical solutions - email me if you would like to discuss it more.

[@MdeLongpre]

+Mitch Peacock - WOmadeOD thanks mitch

[@DwarfDragonwulf]

I learned this many years ago as a "fox tail" joint.

[@mitchwoodwork]

I've never heard it called that before, but I like the name.

[@ianwatters5613]

Great video Mitch , really enjoyed and whilst looks like a real challenge to get it right will have ago on a few practice pieces ! Can you tell us when it is normally or most effectively used on any specific furniture or assembly ?

[@mitchwoodwork]

Ian Watters cheers. Stretchers for splayed legs would be a good use where through wedged tenons wouldn't look nice

[@5ivestring]

Hi Mitch, Great video. If I read correctly in the comments below, you said this joint was made to be able to be taken apart if not glued. I can't see how that could be possible, looks permanent to me. If the wood were to loosen over time due to drying, I could see it becoming a little lose, but never able to come out. What am I missing?

[@mitchwoodwork]

Only in a destructive way, so ruining what was made. I think maybe you were referring to what I was saying on Japanese building joints? Happy woodworking, Mitch

[@AlexPashkov]

Could this one be used for any kind of component's size or is there any limits?

[@mitchwoodwork]

Alex Pashkov The force required to seat the wedges as the joint is assembled will limit the size of components. You can maximize the component size by calculating the minimum thickness the splayed sections should be, and potentially steaming at the base of the slots, where they would need to bend. Do you have something in mind?

[@AlexPashkov]

I just wonder if this joint can be used in construction of the wooden house...?

[@mitchwoodwork]

Alex Pashkov I suspect that would be a little over ambitious for large section timber framing, although I suspect someone will have tried it. Plus, remember this joint is glued, so once assembled it can only be taken apart in a destructive fashion. Therefore, any errors in assembly could be costly. I've been looking into Japanese building joints, and these would be ideal. They are designed to be easily dismantled, yet also be extremely strong, being locked in place with a small wooden pin in many cases. Maybe I will practice a few and add them to my joints series.

[@waveoflight]

I may have missed this but is glue unnecessary with this joint?

[@mitchwoodwork]

Glue should be used, since seasonal changes in moisture content could loosen the wedge and hence the joint.

[@waveoflight]

That makes sense. I really like your videos M8.

[@josecallard]

Good teacher 👨‍🏫 good morning to all 😑

[@mitchwoodwork]

Hi Jose!

[@josecallard]

I wish I cloud take your classes it will be good a spending

[@mitchwoodwork]

Cheers Jose. At least with these videos you have the next best thing.

[@Duh5001]

Mitch, how much of a space do you normally leave at the base of your mortise and tenons?

[@mitchwoodwork]

Duh5001 It depends on the overall scale of the joint, but usually not much. In this example the gap is a little larger than i would normally design.

[@Duh5001]

Mitch Peacock - WOmadeOD tenon 3/4" x 2" in a 3"x3" leg dead center i figured 1/4" recess at the bottom would be enough.

[@mitchwoodwork]

I'd think half that would be fine to aim for. I can't tell precisely what your joinery is going to be: 3/4"x2" - Is this the stretcher or rail cross section, or just the tenon? And if tenon, what is the face dimension. One tenon, or two at right angles? Main thing is plenty of glue surface area, without overly weakening the leg.

[@Duh5001]

Mitch Peacock - WOmadeOD Itd for a bed frame; king size mattress. Three rails on head and foot boards. The tenons are on the end of 2) 2x6s and 1) 2x10 on the top (haunched mortise and tenon). the height of the bottom tenon is 3" tall the middle 5" and the top 7". The Legs are 35" tall, the span is 80" working with southern yellow pine i thought the larger tenon would give me the strength i need for a softwood. I work around a strict budget and hardwood in my area is hard to come by. i used draw bore mortise and tenons on my workbench of the same size and construction. i just wasnt sure if only leaving the 1/2" +/- would be enough to not break out when met with the force applied from the wedges. i love all your jointery videos i try and use new techniques with each new project.

[@mitchwoodwork]

Ah, silly me, I didn't realise you were specifically using the fox- wedged joint. I haven't attempted to fit three of these all at the same time, as you would be doing, and I wish you well! You should experiment with a sample first, testing whether the bottom of the mortise will compress and not drive the wedges in enough (unless you deliberately lengthen them a bit). You could put a 1/8" hardwood bottom in the mortise to spread the impact from the wedge. Also, clamp a hardwood backer on the leg to prevent any blowout/bulging when you're knocking the joints home.

[@andria698]

Can you please tell me what double-sided hand saw you used to cut the wedges? In one of your other videos you used a Japanese saw. Is it the same one?

[@mitchwoodwork]

Andria Denney Hi Andria, Both saws I use are by Noko (available in the UK from Classic Hand Tools). The saw I used to cut the wedges was a Douzuki 240mm Classic, and the 'double-sided' saw that I cut the completed joint in two with was a Ryobi 240mm Classic

[@andria698]

Beautifil work. Thank you for responding.