Tuesday, 5 February 2013

The Chair Back Continued - Some More

I left off last time with the three bent laminations completed and the tree inset carved and ready.  The next step is to join these components together.  To help with alignment during glue up some 1/4" dowels will be placed in the joints between the bent laminations.  An initial set of holes are drilled on the edge of one lamination and then the locations are transferred to the adjacent lamination using some dowel center finders.  I used to use a piece of dowel sharpened in a pencil sharpener....... this is waaaay better, definitely worth the $4.  

Dowel Center Finders in the Middle Lamination
All Three Laminations Doweled and Aligned for Glue Up
The middle lamination will have the center 3.5 inches removed for the insertion of the carved tree.  Once center is found on both items the cutout section can be marked and cut out. 

Aligned for Cutout
The Portion to be Removed and the Angles of the Cuts
The cuts are made using a crosscut sled on the table saw.  The crosscut sled allows for the use of blocks to support the lamination at the required angle and also for the very precise side to side adjustment using screw blocks. 
Aligning the Cut to the Blade of the Saw
Once the waste has been removed from the middle lamination alignment slots are cut along the center of the two halves and the walnut insert.  Using a couple of splines the carved tree will be aligned within the center of the seat back. 

Alignment Slots for the Tree Insert
Dry Assembly - Note the Color in the Canary Wood
Once glued up the walnut insert is shaved flush to the seat back using rasps and sand paper

Leveling the Insert
With a leveled insert the seat back is ready to be shaped.  The edges of the back all have curved edges.  The curved profile of all four edges is the same, so to ensure consistency a model form was made from mdf was copied to the seat back using a template bit in a router table.  This gives the final shape of the seat.  Finally a thumbnail edge profile was applied to the backside of the seat back. 

Seat Back Profiled
As Seen from the Back - Final Sanding Still Needed
Of course while working on the seat back I have been working on all the other components of the chair.  
Dry Assembled - Front View
Dry Assembled - Rear View
Dry Assembled - Seat Back
Now its time for some final sanding and shaping, glue up, corner blocks, and making a slip seat.  So far I'm pretty happy with the look of the chair.  This is the first time I've done one that had compound joinery and it has been a really good experience to work through the problems thus far.  To any woodworkers out there who are trepidatious about building a chair because of the complications in joinery I have to say just go for it.  It was really satisfying and enjoyable.