Tuesday, November 8, 2011

The Rosewood Sofatable (part 3)

The actual construction of the table involved numerous techniques, which covered a multitude of disciplines.

Knuckle Joints -wooden hinges

The main carcase involved a variety of joinery methods from dovetails to tenons. The knuckle joints for the leaf supports were particularly challenging.

Aptly named for their similarity to intertwined fingers, they are in fact simply a wooden hinge. Carved to allow free movement of the sections and pivoting on a steel pivot...exactly like a door hinge.

Close up of the completed joint
Dovetailed Drawers

Dovetial Joint: "A series of pins cut to extend from the end of one board interlock with a series of tails cut into the end of another board. The pins and tails have a trapezoidal shape. Once glued, a wooden dovetail joint requires no mechanical fasteners." 
from Wikipedia

The hand cut dovetails were fashioned into the White Oak drawer sides with a coping saw and then cleaned up with a dovetail chisel.

A time consuming but gratifying operation.

By far the portion of the construction that presented more than its fair share of headaches was the radius-ed boxwood stringing for the legs and the corners of the top. The material I had selected was commercially available boxwood inlay 3mm square. A perfect dimension for the straight sections, bending them to a curve was problematic.

I first attempted to persuade them into the correct radius using a violin rib bending iron. The heat from the iron and the steam produced is quite effective on the thin maple material used for the "ribs" or sides of a violin. After several trial runs, it became obvious that the 3mm thick boxwood wasn't impressed at all with this technique. 3mm was just too thick and the stringing kept shattering into smaller sections.

Given the boxwood apparent desire to be in smaller sections. I ripped 1mm x 3mm thick strips from a board of solid, using the bending iron to get the approximate curvature in each section and them gluing up 3 of these pieces around a dowel,  turned to the proper radius. Each of these assembled corners was them cleaned, trued and cut to fit in its proper place. The corners for the top were done in a similar fashion using a slightly different jig.


As seen on ebay
The veneer was applied to the ground work using a traditional hammer gluing process. The veneer and the ground work are first "toothed". Using a wooden plane, with the blade held almost perpendicular to the surface, the toothed blade both levels the surface of any minor irregularities and adds a surface that is more conducive to adhesion. After toothing the ground work and the veneer are sized with diluted hide glue and allowed to dry completely before proceeding.

Hide glue is made up full strength and applied hot to all the surfaces, using a veneer hammer (seen with the blue handle) the veneer is essential squeegeed down onto the surface and the excess glue is pushed out at the edges. A sticky, messy and slightly smelly operation. Other than the advantage of being historically accurate, the process allows for repositioning and adjustments even after the glue has set. Small bubbles that may occur in the panels can be easily reheated and pressed flat.

Small weight and masking tape can also be used on irregular surfaces to coax the veneer into place until the hide glue cools and gels.

In the case of the curved veneer on the top of the legs I applied sizing to the pieces and sandwiched them between layers of wax paper wrapped around a stain jar. 

The inside boxwood line is glued in place after the center field has been applied and trimmed, and then the cross-banding is applied in the same manner in small sections, with each piece hand fit to the one next to it.

Proceeding around the perimeter until the cross band is complete.

Stringing part 2

After all of the veneer has been laid and dried, I set about cutting in the stringing the highlight all of the edges on the piece. Using a violin purfling cutter, ( I know mixing my violin training with my furniture work) I cut a channel into all of the leading edges and glued the previously made corners and strips in place. Again using masking tape and the occasional clamp to hold it all in place until dry.