haunched tenons

[tmbg]

what's the advantage to haunched tenons, other than filling the groove in the end of stiles in frame/panel joinery? I see a lot of designs, and it almost seems like the haunch was thrown in arbitrarily.

[Mike G]

the haunch covers the end of the dado in the stile that holds the panel. As an extra added attraction it also gives you more glue area which strengthens the joint.

[Jeffo]

My understanding is that traditionally the frame (rails and stiles) for a panel would have been grooved with a plough plane. A plough plane doesn't allow for a stopped groove, so the groove goes the distance of the rail or stile. So you guessed it, the simplest way to fill this groove is a haunched tenon.

HTH, Jeffo

[tmbg]

[jev]

I believe the point of the haunch, especially in non frame/panel apps, is to provide extra stability in the form of resistance to racking w/o having to weaken the mortise by removing too much wood. IOW, you can get a taller tenon w/o getting the mortise so close to the top as to risk blowout in fitting/gluing. Consequently haunches are sometimes used in situations where there may not even be groove needing fill.

[John Crea]

Basically PRETTY is the only reason for haunched tenons. They really are NOT significantly stronger than the non-haunced ones

John

[jev]

[Wes Stewart]

|I'm talking aside from frame/panel applications where you need some way to |fill the groove, like joining table aprons to legs. I've been looking at |a lot of table designs, and a lot (mostly all one guy) use haunched tenons |for the table apron to leg joint, and the haunch seems unnecessary, and |maybe even a liability... |

It is my understanding (and thus why I'm using them on a table I'm building) that the haunch gives extra resistance to twisting of a wide apron, while allowing a narrower tenon. If a wider tenon was used the glue joint could fail due to wood movement.

But what do I know, I'm a realative novice at this [g].

Wes Stewart

[Mike G]

Well then the answer is even easier. For one reason or another all the joints you have been looking at, "mostly from one guy", is that it's the one guy's preferred joint.

While I think it is overkill and see no advantage in it for the extra work to joint an apron to a leg that one guy probably does. Then again, there's no law against overkill in joints.

[jev]

In addition to wider tenon, it allows the deep part of the mortise to be kept further from the top of the leg. When the top of mortise is too close to top of leg you have a situation where that thin piece can be blown out in the process of fitting and gluing the apron. I like to have at least 1/2 inch on top and often keep tops of legs long and then trim to flush with apron after fitting is done but before gluing.

[Jeff Gorman]

"tmbg" wrote

: what's the advantage to haunched tenons, other than filling the groove in : the end of stiles in frame/panel joinery? I see a lot of designs, and it : almost seems like the haunch was thrown in arbitrarily.

Haunched tenons ('thrown in' for centuries) are used at the corners of framed panels.

The haunch is the wood between the end of the mortise and the end of the stile.

If there was no haunch, the end of the stile (of a through jointed frame) would consist of a slot, the joint becoming in effect a bridle joint.

Such joints will have greater gluing area, but are more difficult to cramp up at gluing-up time. To keep the shoulders close, cramps are needed along both the stiles and rails and a 'g' cramp (or similar) is needed to prevent the flanks of the slot from spreading.

Hence, like other features in joints, ease of assembly is a fundamental design feature.

Jeff G

-- Jeff Gorman, West Yorkshire, UK Email address is username@ISP username is amgron ISP is clara.co.uk Website

[charlie b]

For the newbies in the group - when Mr. Gorman responds to a post you can rest assured that you can take what he says as the gospel truth.

charlie b

[Dave Balderstone]

Wonderful explanation, Jeff.

djb