This post is the third and final part of the story of making a sedia tenaglia. The two previous parts can be found here and here. The plan of the sedia tenaglia can be found below.
The plan of the sedia tenaglia. Note that the angle is set at 55 degrees, and this angle also is used for the seating rails. The dotted line left indicates the size of the steam-bending jig. Left is a frontal view, which distorts the actual length of the rails. The dotted horizontal line is the place of the dowel in the centre of the X. The proposed decoration on the head board was not carved as the chair needed to fit with the other folding chairs.
The bended backrest rails were now cut to length. The bending made it difficult to use a normal bench-hook as the rail refused to lay flat. A piece of double-sided tape on the bench-hook kept the rail stable enough to be sawn.
Left: The bench-hook adjusted for sawing the bended rail with a piece of double sided tape. Right: The weight at the bended end of the rail pulls it upwards. The piece of sticky tape keeps it down on the bench-hook.
All the other rails for the seating and the legs were now cut and planed to have the same thickness of 2 cm as the bended backrest rail. The ends of the seating rails were having an angle of 55 degrees. All the rails now needed to have their edges (of the long sides) chamfered. This was done with help of a router table. For the straight rails this was quite easy as they could stably rest against the fence of the router. For the bended backrest rails this was not possible, as the fence interfered with the routing process and needed to be removed. Therefore, these rails had to be stabilized differently. This was solved by adding two pieces of extra wood with a C-clamp at the edges of the rails.
Left: Chamfering the straight rails with the router with help of the router fence. Right: The bended rail is stabilized by clamping two extra wooden blocks at the edges.
After that the holes for the dowels were drilled in each rail. A jig was made for the drill press to be sure the holes were drilled at exactly the same place in each rail (otherwise you cannot construct and fold the chair). Also the drilled holes were rounded of using a cross-hole countersink bit.
Left: The drill jig for the rails of the sedia tenaglia. The rails just have to be inserted and clamped. The stop at the end ensures that the hole is drilled at exactly the same place. Right: The holes for the dowel are rounded with a cross-hole countersink bit. No clamping is needed here, the bit centres itself.
Left: All the seating rails connected by the middle dowel rod. Right: This photo nicely displays the difference in placement of the "X" between the sedia tenaglia and a normal X-chair. Both chairs have the same seating height and are in the same seating position. Not that only four (front)legs are used. The bended rails with the backrest were not yet drilled.
When all rails were drilled the chair was test-constructed. Where needed the rails of the seating and the front legs were adjusted using a belt sander in order to get a flat seating level.
Two views of the chair. You can see on the right photo that one of the rails of the backrest has bended slightly less. However, when the top board of the chair is added, it will automatically be forced to the same bending angle as the other rails. The dowel rods have a thickness of 10 mm.
An 55 degree jig is used to adjust the seating rails on the belt sander.
The final flat seating of the sedia tenaglia.
Now the top board and the rails of the feet had to be added to the chair. A row of mortise and tenon joints was used, which were fixed by two (feet) or three (head) wooden dowels. The tenons were sawn and rounded off with a file. This was done because I made the mortises with help of the drill press - thus producing a rounded mortise - and rounding a tenon was less work than squaring the mortises. A difference nobody will notice looking at the chair.
The sawn square tenon and the filed round tenon.
A set of finished tenons.
Drilling the mortise in the top board of the sedia tenaglia. The jig ensures the holes are placed correctly in the middle. The board can slide within the jig.
Left: The same type of construction was used for the feet rails. Right: The front and back feet rails have a different number of mortises.
After drilling the mortises were cleaned with a chisel.
The feet rails now were having the same angle (55 degrees) as the legs of the chair, meaning they were standing on one point. To have a larger contact area with the ground, the feet rails were planed flat. A spirit level was used to check if both rails were equally planed. After that, the caps were glued onto the dowel rods. Finally, the chair was finished with a linseed oil coating.
The chair was fastened with the seating to the workbench with a clamp; another clamp was used to fix all the rails together. An old wooden Stanley Bailey no. 5 was used to flatten the feet rails.
The finished sedia tenaglia in front of the fireplace at Castle Hernen, the Netherlands.