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The Chair – The arm-backrest joint (part 1)




This is the joint that has been giving me nightmares.


There are issues with grain direction for the joinery. It runs all over the place. Carving sections from solid wood is not a good idea – if I did this design again I would laminate the curves. However, since I am following the original design as closely as possible, I shall let the chips fall where they may. So I shall push forward with the wooden sections I have (not that there is any other choice!).


The choice of glue? Andrew made a good point about epoxy needing a minimal gap of 0.5mm, and that this is not optimised for close-cut joinery. It is better for gap filling. So I shall likely be using hide glue, unless anyone argues against this (the factory used white glue). Which is better on end grain?


A third issue is the finger joint – most importantly, how to line up everything. And to a lesser degree of importance, whether to copy the factory use of rounded ends or go for a pointed finger.


The lining up issue is under control. This post is about the preparations in this regard. The “round vs point” question has me favouring the points because it will be extremely difficult to complete the rounds accurately with handtools. To do the rounds one has to drill through the rail (3/16”), and this must be absolutely square otherwise it will be noticeable. This is fairly straightforward with a drill press (as long as the opposing sides are parallel), not so with a hand drill.


Sawing points is much easier (relatively speaking!). Would this detract from the looks? I don’t think so. The rounds are really quite small and the eye is not drawn to this detail anyway. Your thoughts?


There will be time to ponder this issue since todays post is the last for a week. I shall be back at work tomorrow. It’s been great getting a few hours in the workshop each day over the past few weeks, and I think the progress made has been satisfying. Tomorrow life is back to “normal”.


This is where we left off: blocks of wood dedicated to the two arms and the backrest. A template was made for their plans, and they were marked out.



Large and daunting looking pieces …



The bandsaw was used to saw to the line (the backrest is 5” in thickness and I was not planning on sawing a curve in this with a bowsaw. Let’s get real!). A backsaw will be used for the joinery.


To saw the finger joint for the arm and backrest will be a much easier task if the ends that come together are the same thickness and all ends are square and parallel. This was the task for today. What you see below are the arm ends.



I was still in the mood for woodies. This is a low angle (bevel down) block plane I built.



however it soon became apparent that the LA Jack was better on the wider section of the backrest …



and the Large Veritas Shoulder Plane was the best plane for trimming everything else …




Once all this was done, the sections could be laid together to give you some idea of how they will come together …




A new template was made for the side profile of the arms. The fingers will be sawn first on the arms, and then this will be used as a template for the backrest .. in the same way one would transfer dovetails from tail- to pin board. The fingers here have to be sawn first since they will determine the placement of the fingers on the backrest. It would be too difficult doing it the other way around.


The other feature of interest here is another reminder how much wood is wasted in building the parts for this chair.




Zooming in on the fingers: The distance from the tap/yellow line to the end is 50mm. A rough pencilled line indicates where the backrest would be place and how it would look after shaping.



All comments and advice welcomed.


Regards from Perth

Derek



January 2014