The panel rough trimmed, and cleaned up, a bit, but not leveled, the thickness at this stage is around 10 mm. Final thickness will vary from 5.5 to 7 mm, before final thicknessing the panel will sit in the hot room for two weeks and shrink down. The hot room is set at 26% RH.
I no longer joint sound-board panels with the machine, ultimately the hand plane does a better job. Unlike the hand plane, the machine Jointer produces a series of little scoops, the frequency of which depends on the feed rate of the work. A dull machine also tends to crush the wood cells, rather than cutting through them, which can cause a poor glue joint. At least one manufacturer of pianos is still jointing sound-board panels this way. In the first picture you can see the very simple jig, or shooting board, that I use for jointing thin boards. On some, more traditional shooting boards, there might be a wooden hook at one end to hold the work. My jig uses small C-clamps (see below). With the work clamped in place the board can be planed with the long, 24 inch, jointer plane. This keeps the edge square, and saves the worker the trouble of balancing the plane on the thin edge of the board, were it clamped vertically. How force is applied to the hand plane, determines whet