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Making a Chair – Part Two

May 27, 2011

When I finally remembered to take my chair parts home, I was able to continue the assembly process. The following pictures include a better set describing the tenon cutting process. I begin with the twig cut to its approximate final length, then I round both ends with my modern tenon cutter – Lee Valley. Picture one shows cutter in action. Picture two shows the rounded tenon. Then I switch to my old favorite, the A.A. Woods hollow auger (which is another name for a tenon cutter.) This is shown in picture number three. Picture four shows the final result.

Now, the old fashioned tenon cutter requires some adjusting. So, while it is adjustable for multiple sizes, I much prefer to have dedicated hollow augers permanently set to match a couple of my auger bits. Currently my smaller auger is set so that inserting a tenon cut to the matching drill bit is very tough, but the joint is so strong that glue seems superfluous. A couple test joints that I made this winter, when the air was at its driest, did not budge, and now that there is more moisture in the air and the tenon has probably swelled, I can’t imagine it coming apart. The real test will be next winter, when it has a chance to shrink again.

Once the front and back of the seat, the front and back stretchers, and the rungs of the ladder back are all cut and tenoned, it is time to begin layout the holes to accept the tenons (i.e. the mortises.) If the sides are going to be parallel, then the mortises can be drilled perpendicular to the sides. However, I did not to want the make the sides parallel, but wider by several inches in the front. So I begin by clamping the two sides up with some wood scraps to get an idea of the angle I want (see picture five.) I then use a bevel gauge to record the angle of the parts into the sides (see picture six). The seat stretcher (the part of the seat running across the back of the seat), the stretcher (the part running across the back from one leg to the other) and the rungs (my word, not sure of the official term, for the back parts above the seat) all insert into the sides at the same angle. Because the wood is not milled stock their length may vary. It is easier to drill straight up and down, so I shim up the sides to that drilling straight up and down will mean I am at the proper angle. Picture seven shows the chairs on shims so that the bevel gauge matches a square set on the ground. Picture eight shows me drilling the mortises straight up and down. The angle of the front seat stretcher and the front stretcher is the supplementary angle of the original angle (that is the two angles would add up to 180.) However, since we don’t know the numerical value we can reset the bevel gauge by moving it to the front of the chair, and moving the shims to the front of the chairs sides when drilling the holes. Once the holes have been drilled in one side, there locations must be transferred to the other side (picture nine) and drilled at the same angles. Then it’s assembly time. As I mentioned above, as they are currently set, my tenons are a very tight fit. Ideally one would assemble the whole thing, make sure it fit well, then disassemble it, glue it up and reassemble. However, with this chair, it went together so tight, once it was together, I didn’t take it apart again. You can see in pictures ten and eleven the loose and tightened joints. I do spend some time sanding. I either do this outside or in my shop at school where we have really a good dust collection system. I spend a lot of time on the visible ends of the twigs. As for the bark, I go over it lightly with sandpaper. I like the way the wood still looks rough, but people seem to be surprised by how smooth it feels. After a couple coats of oil, I have to figure out what sort of seat to give it.

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