How are these legs joined to the bench?

[John Pond]

Hey There - making a replica Nakashima Conoid bench. I have got the top side just about figured out but can't find any info on how the legs were joined. Heres a picture of his bench. conoid 2.jpgconoid 1.jpg Thanks for looking.

[Brett Luna]

My guess is they are fixed with wedged tenon in a tapered blind mortise. In other images I found of that bench (or similar) the leg tenons are not mortised through.

[John Pond]

Do you mean something like this (without the square base)?wedge tenon.jpeg Sounds tricky, my legs are turned like the original. So would you mortice a circle and insert the leg about 1'' into the bench if the slab was 2''? Any ideas for the size of the wedge? I.e should the wedge be 2 inches and protrude beyond the mortise. Can anyone recommend some reading material or tips for wedge proportions? I had concerns about the stability of the legs without any stretchers and without a splaying of the legs. Does anyone know whether the mortise will suffice in avoiding any future wobbles? Thanks again

[Michelle Rich]

nothing more than windsor chairmaking skills..study that and your legs will be very strong.

[Chris Friesen]

nothing more than windsor chairmaking skills..study that and your legs will be very strong.

I think in a Windsor chair the legs usually join to the seat with through-tenons. Some of the comments above implied that these were blind, in which case a fox-wedged tenon would probably be strongest.

[Pat Barry]

What thickness is the seat? What diameter are the legs at the surface level? Just thinking out loud here, the wedged tenon advocated above is probably your best bet although I'm thinking that having a tenon on the leg that is a bit smaller diameter (maybe 1/2" less for example) than the leg itself would facilitate having the leg be drawn up tight to the underside of the seat with a relatively large surface area that should provide a lot of structural strength -- more than just having the leg fit into a hole.

[John Pond]

That sounds like a good idea, I could see how that would work nicely. The slab is about 2'' thick, what would you say the best depth for the tenon?

[Davis Young]

I did something like this for a claro walnut bench except the legs were blind wedge tenoned into the armrest which was considerably thinner than your 2" seat slab so there was less margin of error in my case. If it is to be a blind mortise, consider squaring up the tenon, even if it is for a round leg, for a couple of reasons. One is that it will be easier to taper the mortise with a chisel than a gouge. You will need this control because you would like to have a nice fitting taper. Too loose and it could be wobbly. Too tight and the joint might not be able to close. And it's not like you can do a dry fit. Another reason is you will get long grain to long grain glue contact on two of the m&t surfaces. At 2" thick I would consider going as deep as 1-1/2" to get as much contact as possible. The only dry fit you can do is with the leg (without wedge) into the mortise to see if the mouth of the tenon is tight and the shoulders are good. Also, though you have to take great care, you could also dry fit the wedge into the leg (without inserting leg into mortise) to see if the proper amount of splay is achieved and if the wedge will not protrude when it bottoms out. The risk here is that the wedge could get stuck and be hard to take out and more importantly the wedge might split the leg without the counteracting force of sitting in a mortise. I would recommend clamping the leg in a vise while testing the wedge. On my bench, I remembered psyching myself up for the better part of a week before the glue up but after all my excuses to put it off ran out, it went together without a hitch and I wondered what all the fuss was.

[John Pond]

You're right that does sounds a little easier. The legs I'm hoping to use are about 1&5/8'', making the squared tenon about 1&3/16''. Does that sound to small? The Bench is about 8-9ft long with an average width of 20 inches ?

[John Pond]

Also what amount of splay am I looking to achieve? If the tenon is 1&3/16, what would the be the new dimension with a wedge, and also the ideal wedge size. And how should I taper the mortise, ie. when would the taper begin if I were to make it 1.5'' deep? Should I expect the splay to be exactly proportionate to the width of the wedge from top to bottom. For example, if the wedge is 3/16'' at the top end, but tapers to an 1/8th at 3/4'' down from the top, will the tenon size increase by the 1/8'' down 3/4'' from the top as well? And where should I place the wedge relative to the grain direction? I may just have to do an test run, I just wish I had more of the same material to do a test run on.