JOINTING THE SOUNDBOARD.
Last week I made two jigs in preparation for this phase: A general shooting board for truing edges and a center seam gluing jig for gluing the two soundboard halfs together. The gluing jig is very basic and consists of a flat surface with a stationary fence on one side and a adjustable one on the other. The actual clamping pressure is provided by tapping two small wedges together in between the adjustable fence and the soundboard itself. A caul that runs along the joint is held in place by two cam-clamps and keeps the two soundboard halfs from buckling up under the clamping pressure. This last jig will also be used for the jointing the back.
The soundboard came with all the saw marks from the mill and the first thing I set out to do was to plane the faces clean and smooth. I carefully planed it with even, slightly overlapping strokes, slowly working my way from one side to the other. The boards were not clamped to the bench, just butted up against a benchdog raised about 1/16". The planing created a lot of static electricity and it was quite annoying to have the shavings and dust sticking everywhere. Taking cellophane of a CD jewel-box comes to mind - once it is off you can't get rid of it.
Once all four faces were smooth I closely inspected them to get a rough idea of what might become the in and outside of the top as well as with which sides they should be jointed, based on the grain pattern, medullary rays, blemishes etc.
The grain direction at the center seam formed a slight 'V' along the seam. To remedy this the boards were clamped in the shooting board with light clamping pressure and and I started shooting with the jack plane fairly coarse set until the the edge ran parallel to the grain. Then I adjusted the plane to a finer set and shot along the entire edge a couple of times, unclamped to boards and held them up towards a strong light with the edges butted up against each other, only to reveal that the center seam was only touching in the middle, letting light in at both ends. The lights I used were two 100W bulbs in aluminum reflectors.
I clamped the boards back in the shooting jig and started planing the middle, slowly working my way towards then ends, making the strokes longer and longer every time the plane stopped taking anything off. Once I reached the full length, I set my plane to the finest setting I possibly could and shot a few last strokes, unclapmed the boards again and held them up against the light. This time the center seam proved tight and closed along the entire length of the boards, not letting any light through the seam. The two halfs were ready to be glued.