This working process was instructed by the shop owner Mr. Jude Reveley.
The shop owner designed the species, length, width, radius, etc. of the new ribs on the Steinway L being rebuilt. We are going to have the ribs made today. According to the data sheet, pick the wood - Sugar Pine for rib # 1, Sitka Spruce for rib # 2-11. Discard wood that has flaws, such as splits and knots. When selecting wood, make sure each rib is at least 2mm taller, 4mm wider, and 10cm longer than spect. The ribs will sit on soundboard with grain vertically placed. All ribs are quarter sawn.
Chop each rib to ideal length plus at least 10cm. For shorter ribs, use one stick of wood for two ribs. Waste as little as possible. After chopping, mark the number of each rib. Number direction goes with grain, vertically placed.
To save time, Group ribs by similar height. Plane each group 2mm taller than the tallest in the group. Before running them through the planer, mark top and bottom side with pencil or crayon. Plane top, then bottom, then top again, back and forth to target height and all marks disappear. These pictures show rib group #1, 9, 10, 11, target height 15+2=17mm. Be patient, double check the numbers. This job seems lasting forever, yet we don't want any mistakes caused by rushing.
Place rib making jig and cauls at a convenient area. The caul radius range from 4m to 15m. Each radius set includes bottom caul (concave) and top caul (convex).
We'll take rib number 11 as an example here. The rib making jig jams rib in to a channel, the little pins in middle picture fasten rib stocks in the channel when it is closed. One or multiple shims are placed under bottom caul to adjust rib height.
The center of cauls and the jig is marked. At the center, the distance between top caul, with shim underneath, and the surface of jig is almost 8.69mm. We call it 9mm giving room for screw ups. The jig is 73.86mm thick, say it 74mm. Target height of rib #11 is 14mm. So after milling, top of rib to bottom of jig shall be 74+(14-9)=79mm. The protrusion of rib over jig is 14-9=5mm.
Place rib stock #11 in the channel at center of jig, place top caul and clamp down very tightly till there is no gap between the surface of rib and caul. Close the channel by screwing in the metal push sticks. The little pins will hold the rib in place. Unclamp the top caul and put it away.
Make sure there is a support to hold the jig on the other side of saw, same height with table saw surface. We ran out of roller stands. A work bench was placed there later on. Raise the saw blade high enough to cut ribs in jig.
The target width to mill is 79mm, yet it is set at 84ish on table saw since the tape measure on the saw is not very accurate, and we want to leave the final height trim to the planer. Sawstops are sensitive to metal. There is plenty metal on the jig. So the safety function on the saw is turned off by turning the key, then turn on the machine. Now, pay close attention to everything around the saw especially our body. Good luck finding replacement parts if loosing any, it can be our lives, too. Run the whole jig through table saw, hold on to the jig with a hand, shut machine off, wait until the saw blade stops completely before removing the jig.
At planer, make sure there are supports at each end of the machine, slightly lower than planer surface: jig thickness + top of rib that is sticking out. Mark surface of rib with pencil or crayon for plane result observation. The protrusion of rib above jig surface started at 6.95mm before the plane, and 5.08 afterwards. Close enough.
Clamp the jig on a sturdy surface, sand rib top till smooth. It takes only a few strokes if the planer is set up right, springs not too tight, and the blades sharp. Scrape with a bent razer blade till a smiling face is present through the length of the rib. This surface will be the glue surface between ribs and soundboard.
Draw a line at center of rib and number it. Turn back the push sticks, open the channel, take out rib, and check thickness. Interestingly the rib was concave in the jig at the beginning. By shaving, it springs out with an arch afterwards. Maybe it is because the wood cells are opened up. Our target height is 14mm. 14.5mm here is acceptable since we are going to do more work on the ribs which may reduce the height. It is better slightly taller than too short.
If the rib is still much taller than target, run it through jointer to the ideal height plus about 0.5mm. The milled ribs make one smile, don't they. But we are not done yet.
The ribs then are trimmed to width. Group ribs to similar height. Adjust saw blade to the tallest rib in the group, saw one side, leaving 2mm room for the other side, then saw the other side. The result shall be about 0.5mm wider than target. We'll put marks on the sides later on when fitting in piano, then send the marks off, which will reduce the width.
Already, all ribs are milled and ready to be fit in piano. Time to go home. Good night, Steinway L! Thanks to Mr. David Betts who's spirit encourages us to move on with passion and care.