Got a chance to do a bit more on Saturday. Stargazer spotted that it is unusual to be working on the top part of the chair before sorting out the undercarriage. I think I mentioned part of the reason earlier, which is that I wanted to do all the drilling in the seat and arm bow before shaping them, so I had a nice flat surface for sight lines and to stand my square / sliding bevel on for checking the angles. But what I forgot to mention is that I did drill the leg sockets in the underside of the seat at the same time as I did the holes in the top side for the back spindles. The method is just the same though, with brace and bit and sightlines for alignment.
What I hadn't done is drilling for the stretchers. Again Jack Hill's book gives partial information about these angles, and I didn't want to trust them blindly, so I checked them in two ways. First by a fair bit of trigonometry; knowing the orientation of the sight lines for the legs, and the angle and position of the leg sockets in the seat, it is not too complicated to work out the lengths of the stretchers and the required angles. But I didn't trust my maths completely ... so I found a simple way. Assemble the seat and the legs, mark on the legs the height where the stretchers will go. Then place a
large elastic band around the legs at that height, measuring the angles between the centreline of each leg, and the rubber band using a combination square. Amazingly this all agreed, so we can start drilling !
One more useful tool is a Mike Abbott style centre finder:
By sitting the bird's mouth over a spindle, the nail can be stuck lightly to make a starting centre for the drill nicely in the middle of the leg.
Here I let my purist approach slip. Although sharp, the augur was just too brutal for boring into the legs. The combination of the angle of the hole and the convex shape of the leg meant that the spur didn't scribe a nice circle, and the risk of splintering around the entry of the hole was too great. A forstner bit makes a much cleaner hole, and the cordless drill was to hand. I still regret it a bit though. It is the only point at which I've reached for a power tool, and I could have used a breast drill maybe. Oh well, it's done now. A couple of V blocks help to hold the leg down, whilst again using the pair of squares to judge alignment:
Another trial fitting, and measuring to check the drilling angles for the lateral stretchers, then the final trial fitting:
You'll spot that in the intervening time I've scooped out the seat a bit, using the outline of my backside I drew on earlier in white pencil. Jack Hill says "by any safe method", I was going to rough out some of the waste with a really heavy Henry Taylor sculpure gouge, but it seemed a very noisy and energetic process, so I used my homemade travisher again. The travisher is a somehow very theraputic tool to use. At the same time I rounded and lightened up the arm bow with spokeshaves, Iwasaki rasp and card scrapers.
Now comes the stage I really love. The assembly. After days (months more like) of shaping parts, in the space of an hour it becomes a chair ! This particular assembly was a novelty for me, because glue was involved. My previous 2 chairs were made from green wood, and needed no glue, just the drying shrinkage to hold them together. In this case I had planned to use Titebond liquid hide glue for the longer open time. Andy's suggestion of testing if my open bottle was still OK by gluing a couple of bits of scrap together seemed like a good idea, but my glue failed an even simpler test - is it still liquid ? So I used Titebond 3 instead. This made for a frantic hour. Assembling the seat/arm bow/back spindles very nearly caught me out; the joints were a good snug fit, but after applying water based glue to all 32 surfaces, the spindles began to swell, and it was more than snug ! A good bit of wrestling and persuasion with a big mallet was needed, but here's where I'm at now:
It's a shame about the fuzzy picture, but it had gone dark by now. The old blanket, incidentally, was to allow me to work on the floor without getting scratches from grit all over the seat whilst assembling the legs and stretchers. Learned the hard way on a previous job.