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haunched tenon joinery . . . how big a difference? when needed?

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Forum topic by JohnR posted 06-21-2008 04:19 PM 7609 views 0 times favorited 9 replies Add to Favorites Watch
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JohnR

43 posts in 2352 days


06-21-2008 04:19 PM

Topic tags/keywords: haunch joinery tenon mortise question

I have been looking at several sites that show examples and methods of/for the use of haunched tenon joinery. While I admire the skill set needed to create such, I still don’t understand whether it would ever be considered “necessary”, and how big a difference/improvement the use of such a joint will provide over a standard mortise and tenon joint.

Anyone care to enlighten this neophyte woodworker?

Thanks, as always, for your courtesies.

-- Sola Gratia, John


9 replies so far

View GaryK's profile

GaryK

10262 posts in 2643 days


#1 posted 06-21-2008 04:27 PM

It’s mainly for looks. Nothing necessary about it.

-- Gary - Never pass up the opportunity to make a mistake look like you planned it that way - Tyler, TX

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teenagewoodworker

2727 posts in 2423 days


#2 posted 06-21-2008 04:42 PM

for looks but also for big solid wood entry doors. if you have a nice big solid mahogany entry door you need the groove there for the panel. a tongue and groove might cut it but a haunched tenon would add that extra support of a mortise and tenon but the haunch is so it fills the groove for looks. other than that the haunch isn’t necessary. it is the mortise and tenon that is

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Harold

310 posts in 2502 days


#3 posted 06-21-2008 05:38 PM

I use haunched tenons primarily because the “painter” who taught me used them and I wasn’t given a choice. I do believe the additional shoulder area does increase the rigidity of the joint in traditional joinery where wood movement must be accounted for….I don’t view it as a additional step in setup or layout…but once again it was just the way I was taught…...there are many options and techniques available today.

-- If knowledge is not shared, it is forgotten.

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Loren

7556 posts in 2302 days


#4 posted 06-21-2008 06:41 PM

It fills the gap in the groove for the panel. These
grooves were at one time cut with hand planes,
so they could not be made “stopped”.

In delicate work with thin rails/stiles the haunched
tenon can be used to provide a little more support.

-- http://lawoodworking.com

View Mark Shymanski's profile

Mark Shymanski

5111 posts in 2367 days


#5 posted 06-23-2008 12:46 AM

I’ve also read about haunched tenons being used in framing construction for buildings. The haunch part apparently adds considerable bearing load strength to the joint. If you think about the stresses on the horizontal member of a framed building the ‘extra’ material supported by the haunch makes the member all the more rigid, and capable of carrying that much more load. In smaller applications I can see that the haunched M/T is for appearance, but I believe that in framing it is actually a stronger joint.

-- "Checking for square? What madness is this! The cabinet is square because I will it to be so!" Jeremy Greiner LJ Topic#20953 2011 Feb 2

View frank's profile

frank

1492 posts in 2860 days


#6 posted 06-23-2008 02:52 AM

Hello John;

—-and yes, if you’re still wondering….I hope I can help.

Through haunched mortise and tenon....Secret haunched mortise and tenon and, so in my own words let me add: ”....haunching the tenon creates an extension of the tenon at the start of the tenon, by adding a ‘shoulder’, which in turn gives extra strength at the end of the mortise….”

Now if I may let me also add/quote from one Sam Allen in his book Wood Joiners Handbook and page 96.....

Haunched Tenon

The haunched tenon has a notch cut on the top cheek. This creates a short stub tenon that extends to the end of the board. It strengthens the joint by adding support in this area that would otherwise be left unsupported. The haunched tenon is well suited for use in panel-frame construction because the tenon will fill the same groove that has to be made for the panel. If a haunched tenon is not used for the panel fame, then the groove must be stopped. The standard haunched tenon can be used as well in parts that are not grooved for panels, but you can also use a secret haunch that will not show on the end.”

—by Sam Allen; Wood Joiners Handbook

Let me also add that in my learning and studies into ‘wood joinery’, I myself was first learned from the western tradition of thinking, that much of the extra’s of making wood joints, (beyond the strength of the joint) was much about what one sees in regard to appearance….and the woodworkers ‘ego’. But that was in the ages of ago that I left ‘western thought’ to where I am at now in the ‘eastern thought’ of wood joinery.

In my studies I first went after early Japanese wood joints, but that soon lead me to earlier Chinese and Korean masters of these joints. What I learned was to first forget all that I had been taught by western thought into wood joints….and the need to show the joint off. I came to learn that dovetails were one joint that early eastern woodworkers learned first and then moved on to the more sound but hidden joints. I mean when you come to think about it, were does ‘ego’ fly when you are doing a ‘secret haunched tenon and mortise’ and yes, you can tell folks it’s there….but how are they going to know when no-one sees it?

....and no, I don’t speak on this much anymore, since we are western thought woodworkers and…..those who know eastern thought of woodworking….well they have all-ready conqured the ‘ego’ thing….

Hope this helps and….,

Thank you.
GODSPEED,
Frank

-- --frank, NH, http://rusticwoodart.tumblr.com/

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moshel

864 posts in 2338 days


#7 posted 07-04-2008 03:51 AM

Frank, I would love to learn about the joints you mention (sound but hidden). maybe a blog?

-- The woods are lovely, dark and deep, but I have promises to keep...

View 4hemispheres's profile

4hemispheres

1 post in 998 days


#8 posted 12-26-2011 06:55 AM

Just for looks? Huh This technology is centuries old and exists for a VERY good reason.

Haunched tenons resists “racking” (downward diagonal force) better than the regular mortise and tenon because the elimination of the extra material on top reduces the surface leverage of the remaining tenon surface against the walls of the mortise top down.

I use this any time I have a heavy use piece that needs to resist shifting or bumping from the top like counters or butcher boards. The top and bottom joints of doors can benefit from this as well.

As far as looks, this looks less seamless than your average mortise and tenon so I don’t understand what people are getting at by that.

-- Be honest in what you design

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Sylvain

553 posts in 1154 days


#9 posted 12-26-2011 05:18 PM

Hi everybody,

my understanding is:
- the tenon and mortise main function is to keep the place of the two parts in relation to each other;
- the shoulders are providing a bearing surfaces to ensure the angle between the two parts remains what was intended (generally 90°) even under stress.

My reasoning is that you are never completely sure how the tenon and mortise are fitting.
Furthermore, if they are not glued like in pinned tenons or tusk tenon or tenons with bed bolts (like in some workbenches), the shoulders are clearly what is ensuring the correct shape of the assembly and the tenon and mortise don’t even necessarily need to fit perfectly.

The haunched tenon gives you the double benefit of an “increased gluing surface/bigger tenon” and an extra bearing surface. The extra bearing surface gives extra resistance to deformation.

-- Sylvain, Brussels, Belgium, Europe - The more I learn, the more there is to learn

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