Thread: Is this joint strong enough?

Nice work Bart. Those tenons are beautifully done, i suspect you have a pantorouter or something like that?

I can see why you would be concerned about the strength given that the whole rear leg assembly is only joined by that 30mm long tenon. Personally i would make the rear stringer wider to get a longer tenon. That might lead to wider sides too which i can understand would be undesirable if you are aiming to have these stackable.

Please post your solution when you're done. Always enjoying looking at beautiful work like this.

I am happy with it. Add a wedge or 2 to the tenons would be even better. Good work I like it.

Hi, in my opinion as your chair has no lower legs rungs which add consireable rigidity to a chair then no probably not.

Almost certainly with time the stress of use on the back will cause the joint to fail or loosen.

I am not a chairmaker but have dealt and restored much furniture in my time and have seen my fair share of wobbly chairs.

I would prefer a much deeper and/or thicker side rail.
This is just my thoughts and others will doubless agree or disagree.

Thanks for the valuable feedback and kind comments.

Lplates & Mark, What you have both mentioned about the rear stringer being the weak point is my concern as well. I didn't want to make it any taller as I thought it would add visible bulk to the chair but I certainly could have made it thicker with longer tenons which would have added strength (got just enough timber left to remake these pieces).
Wongo, I like the idea of putting splines in the through tenons and I think some jarrah for contrast would make the joinery stand out nicely whilst providing strength.

The tenons are 40mm x 1/2 inch and were created on a pantorouter.

Once finished I suspect that I'll be the only one who can sit on these chairs for a while just in case.

Hi All,
I'm not a Chair maker either, but have had trouble in the past of Chairs like that, mainly because of no Stretchers. I was always trying to fix them until somebody lashed out & bought new ones with Stretchers.

My understanding of how chairs were traditionally made is that you didn't want the joints to be particularly strong - or at least not rigid. I'm talking antiques here. You glued them up, they got wobbly after a few years, you split them apart and glued them up again - on and on every few decades. Just regular maintenance, really.

Hide glue made this easy.

The alternative was to try and make them quite rigid from the start with wedges and pins etc, but this was considered bad form because it made it more likely that the actual timbers would crack, which couldn't be repaired. Much better that they gently fell apart at the joints and were easily repaired.

Nowadays of course we don't expect chairs to last so they are made rigid with screws and wedges and irrepairable glue and thrown out when they get wobbly.

So, yeah, the rail sections are rather thin and oregon is a bit splitty so will probably crack if you glue them up too rigid. The lack of stretchers will also have the legs wobbling around a bit in a few years. Up to you whether this is a problem.

cheers
Arron

Another 'not a chair maker'. I think you would possibly get away with this if you were using hardwood, but I doubt that oregon has the qualities required to stand the test of time without stretchers. I have seen similarly constructed chairs made of pine WITH stretchers fail over time.

Is that a home made vertical mount router jig I see in the background? Is this how you cut your mortices and tenons? Nice job on the mortices and tenons so obviously you've done a nice job on the jig. I have made an adjustable jig with the router operated horizontally, which I have mounted to the side of my bench. Only problem is the limited length of stretcher members, bloody floor keeps getting in the way! I would be very happy to cut joints of the quality of yours.

David

Add some corner blocks (glued and screwed in) and it'll be fine.
I make chairs (and all other kinds of furniture as well) for a living and I'd be happy to give a lifetime warranty on those tenons with corner blocks.

I'm not keen on the idea of making something which will need to be repaired in the future. This is my first chair project and I have never done any restoration before so my expectations might be a bit high.
These chairs are really just an experiment and if they prove suitable I will probably make some more of a similar design using jarrah which is fairly common if willing to do the rounds at verge collections etc around this area. If they can handle my weight with oregon then I expect using jarrah will take the doubt away, the only concern then is the weight but there's always a trade off.

David, the jig in the background you saw (see photos) is something I came up with for making the chair seats. It's essentially a gimbal (universal joint) which holds the router approx 700mm below which I used to create the seat scoops. The idea of carving a seat just didn't appeal to me and I doubt I could make two the same so after searching the net for something and coming up blank I thought there has to be a better way. I'm sure this method has been used before but I couldn't find any references after a few hours googling. It may look a little unsafe but is very easy to control in use and I put clamps on the gimbal to limit travel, dust and shavings are another matter entirely though. All the M & T joints were done on a pantorouter I built from the woodgears website plans.

A bit off topic, but a couple of years ago made myself a horizontal morticing router tool
I don't cut any tenons now I just make my own loose tenons and can make a table frame or similar with a total of 16 mortices and 8 loose tenons all cut within about 30-60 minutes.

Being horizontal I have no limitation on the length of any timber used.

Unfortunately chairs do get rather abused and this hastens the joints to a rapid demise.
Come to think of it not just chairs though, I once had a Regency period card table that had all four legs broken off !

Originally Posted by aldav

Another 'not a chair maker'. I think you would possibly get away with this if you were using hardwood, but I doubt that oregon has the qualities required to stand the test of time without stretchers. I have seen similarly constructed chairs made of pine WITH stretchers fail over time.

Is that a home made vertical mount router jig I see in the background? Is this how you cut your mortices and tenons? Nice job on the mortices and tenons so obviously you've done a nice job on the jig. I have made an adjustable jig with the router operated horizontally, which I have mounted to the side of my bench. Only problem is the limited length of stretcher members, bloody floor keeps getting in the way! I would be very happy to cut joints of the quality of yours.

David

Originally Posted by Wongo

I am happy with it. Add a wedge or 2 to the tenons would be even better. Good work I like it.

Originally Posted by mitzee

Wongo, I like the idea of putting splines in the through tenons and I think some jarrah for contrast would make the joinery stand out nicely whilst providing strength.

The tenons are 40mm x 1/2 inch and were created on a pantorouter.

What Wongo is refereing to is a wedge not a spline. The mortice should be cut with a slight V at each end (so that is is wider on the rear face compared to the front face) and the wedge expands the ends of the tenon just enough to make mechanical joint.

search for "fox wedge" joint

Thanks for the clarification Ian.
In my reply to Wongo I said splines but I was thinking dual wedges (lack of experience and familiarity with the terminology).
I looked up 'fox wedge joint' as you suggested and although I do believe I could accomplish this modification to the mortise I wonder if there would be any real advantage in practice when considering the strength of modern glues like Titebond 3. Many of the glue tests I have seen show the wood failing before the glue when used in a long grain to long grain joint. I have only been woodworking for a couple of years so nothing I have made has been around long enough to see how long the glue retains it's full strength. In the event of the glue weakening with age then the fox wedge joint you pointed out would definitely make sense.

Hi, No comment re the construction except adding that what wongo has added I agree with. I do question using oregon. Its a soft brittle timber and as the chair racks the fibres will compress and the joints will become loose. I question the longevity of your chair (Unless its a mock up for a design...)