Help with chair design and joinery selection

mardi 27 mai 2014

Apart from a simple chair made for a three year old, I have never made a chair. Time to start.



Decided to make a new dining suite. The table will likely be a pumped up version of a recently made coffee table, because I like the look.



But then there are eight chairs to be made. Having discovered that cabriole legs are time consuming, but not really difficult, I decided they were the go. Have fiddled about with design, and at this stage a likely candidate appears below.



IMAG0644[1].jpg



Most chairs are about 900 mm high, but I think I'll keep mine to about 800 mm high, a bit like a Danish chair.



The legs and frame I can do with my current skill level. I even reckon that without too much grief I can make the bent/shaped backs. The trouble I have right now is deciding how to attach the back to the frame. The intention is to join the bottom of the two side pieces with a piece of timber about 40 mm high, and mortice and tenon joints are the plan. That should give me a back that is reasonably strong.



My question is, how might the back be attached to the base? I have thought of several approaches. It seems that mortice and tenon would be a strong joint, but I am unsure of how to do that. The base won't fit into my morticer, so the mortice would need to be cut into the frame before assembly of legs and frame. Then these mortices would need to be extended by hand into the tops of the legs. Then comes the issue of cutting the tenon so it is vertical to the floor, and at an angle to the back. I was thinking of making up a jig to hold the back flat, tilting the table saw a tad and then cutting the tenon on the table saw with a dado blade.



So, I'm on the hunt for ideas and alternative solutions. The easiest solution is to rip off about 3 mm from the top of the 40 mm piece mentioned earlier, glue and screw the back to the base, insert a 10 mm dowel through the 40 mm section into the base every inch or so and then to glue the 3 mm section back on over the tops of the dowels.



Easy, yes ... but is it strong enough? ... My thinking is that if the base of the back is about 30 mm thick, and if it has a dowel every inch (or even less, if required) that the 12 (or thereabouts) 70 mm long dowels should give a strength similar to a set of floating tenons ... but is this correct?



EDIT: Just had another thought. I could cut the mortice in the frame before assembly, and at the same time cut another mortice the same size (say 12 mm) into the 40 mm section at the base of the chair. Then a floating tenon the full width of the frame is glued into place. Alternately, I could cut the tenon into the base of the back before assembly with a dodo blade. Any more ideas?


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