The Chair – Close but no coconut
I spent the time I had this weekend sawing fingers … Wegner fingers, that is.
It was a bloody business ...
A decision has to be made about this joint – does the shape end in a point or a round? The original chair has finger joints that end in a round point, not a pointy point, and so I would like my chair to have the same. As I showed in the previous chapter, this was the default shape created by a machine, and unlikely to have been deliberately designed into the chair. Indeed, the finger joint was added by the factory to increase the strength of the join between arm and backrest; it was not the design of Wegner, per se. Although I am sure that Wegner hand built the prototype, I very much doubt that there is some earlier version that has a pointy finger joint. As far as I can ascertain, the connecting joint was a “square dovetail” which was hidden under a rattan or cord wrap. Subsequent Type #501 chairs were built with the rounded finger joint of the Type #503 ..
What I discovered this weekend is that I can make this joint. I cut a few perfect examples. However, it is extraordinarily difficult to do, and the expected failure rate is somewhere about 80%. I believe in the woodworking of risk, but not the woodworking of suicide.
My intention today is to show you the method I used to cut this joint, and in some detail. Please feel free to critique the way this went. The detail is also relevant since it demonstrates just how complex the joint is to create with handtools. Below are some of the tools used ..
For practice I worked with European Oak scrap about the same thickness as the actual work pieces. The oak had been planed and thicknessed by machine. The conditions were optimal.
I chose to work with a drilled hole through the wood along with two connecting saw cuts through the wood. I do not see any point in working from the outside towards the centre since the sides will be carved away and the centre will be left. The only way, as I see it, to ensure the centre section is true is to make it so the full width of the wood.
A Finger
The first step is to create two lines, the first 50mm from the edge (the length of the finger) and the second half of 3/16” (the hole being 3/16”) inward from the far line.
The base of the finger is 25mm wide. This is created by 2 x 12.5mm marks …
Extend the centre and mark the first line …
Drill a 3/16” hole at the first line through the full width of the board. The hole defines the upper end of the finger.
This hole has to be perfectly vertical because anything else will leave one side of the joint off centre to the joint on the other side of the board. As always the plan is to do this with hand tools.
I created a jig to drill the hole. I would have liked to use a Stanley #59 dowel guide but it was too narrow to extend across the work piece.
The jig begins with a vertical V against which is clamped the 3/16” dowel guide from the #59.
There is a rebate at the lower side for visibility ..
Below right is the hole drilled (there is another hole on the left I shall explain shortly) …
On the reverse side of the board it can be seen that the hole is perfectly square as it bisects the same line. The second hole (on the right side of this picture) is elongated. I attempted to use a brace and discovered that it is not possible to prevent it moving back and forth. The “good” hole was made with a battery-powered drill. Is there such a thing as a 3/16” wide auger bit? The smallest I have is ¼”. The 3/16” twist drill bit used is not suited to a brace (it requires too much downforce, hence the rocking), and the wood is too hard and too thick for an eggbeater.
To complete the marking of the finger, one side is aligned from the base to the edge of the hole …
A Glen Drake Kerf Starter was used to score the line as the thick blade is less vulnerable to follow the grain, and the kerf it creates offers a better visual guide to place the saw than a thin knifed line.
The kerf starter …
This is repeated on the other side …
The second jig I built was a guide for the tenon saw. The need for precision demands this. For example, there is no leeway when sawing to the circumference of the hole. One either saws into the hole, or misses it.
What I built was a L-shaped section that used rare earth magnets to clamp the saw plate.
The guide is clamped to the work piece, aligned with the saw kerf …
… and carefully checked for absolute square.
The view below is from the other side of my leg vise. First the work piece is angle at 45 degrees and sawn towards the hole …
Once the saw has enough depth, the work piece is turned to vertical and the direction of the saw is now across the end grain (hence the magnets placed around the side).
Below is one completed saw kerf. I would rate this side 100%.
Rotating the board (picture below) – I would rate the cut on this side about 95%. There is a tad of drift into the hole. It is not fully on the perimeter of the hole. This could be repairable with a little chisel paring.
The other side of the finger is set up and sawn in the same manner. The only change is the use of a scraper blade. The magnets hold it to the side of the jig, and it is easy to place it in the kerf created by the kerf starter. Again, this is checked for vertical.
And again the side of the finger is sawn in two operations …
On this side it is good – ignore the fact that I have overshot the line (a lapse of concentration at this point). Basically, this is what is wanted.
The waste section is removed …
The reverse side of the board reveals that the saw missed the circumference of the hole.
When I examined the internal sides of the finger, one side was perfectly square and the other was not. What happened? Perhaps the jig was not clamped as square as I thought. Perhaps the saw drifted in the cutting. Perhaps I pulled it across with pressure.
I do not know. It could be any or all. I sawed about 8 or 9 finger joints today, and 2 were perfect. The others all had some issue.
Can I improve on this? Possibly, with more practice.
What I did do was mark out a pointed finger and, without a jig, sawed it by eye. This is what I got …
Reversing the board shows a decent fit on the reverse side.
My experience here is that the rounded joint can be made, but that the quality of it is not to the standard I would want.
Would you go with the pointed finger, or keep practicing? Is there an alternative method?
If I eventually end up with a pointed finger, it will not be for lack of trying to master the rounded point, and there will be the realisation that the chair with the rounded joint is made by machines, and the chair with pointed fingers is made by hand. I could live with that.
Regards from Perth
Derek
February 2014