The Manufacturing Process
Bending the rim of the case
1 Steinway’s method of rim bending is still used and is the first step in assembling the grand piano. Layers of long-fiber maple wood are glued together and bent in a metal press to form a continuous rim; both the inner and outer rim are made this way. Up to 22 layers form each piano rim, and the layers may be up to 25 ft (7.62 m) long. Resin glue is applied by machine, then the layers are carried to the press where they are shaped. The rims are stored in braces to keep them from changing shape. They are seasoned in controlled temperature and humidity conditions until the wood meets a specific moisture content where it will hold its contour. The bent inner rim is then fitted with other wood components, including the cross block, the pinblock, the cross braces, the keybed, and the backbottom. These are glued and doweled in place.
2 The cabinet is finished to improve sound properties as well as for appearance. The cabinet is sanded so stain is absorbed properly, wood is bleached to equalize appearance of the veneer, prestaining and staining are done next, wood fillers (sometimes with a washcoat) are added, and a first coat of sealer or lacquer is applied. The surface is sanded again, special glazes (for antiquing or other effects) are added followed by two more coats of lacquer, sanding is done again, special trims are added, and two final coats of lacquer are used. The cabinet is dried for up to 21 days before it is hand-rubbed to its final finish.
Making the structural components
3 The wood components of the piano (collectively called the framework)—the pinblock and the cast iron plate—are the parts of the piano that support the tension of the strings. Braces are made of select spruce, and the pinblock or wrestplank is constructed of bonded layers of rock maple. The pinblock is quarter-sawn or rotary cut to maximize the grain structure’s grip on the tuning pins. The laminated layers are also glued at different angles to each other so that the pins are surrounded with end grain wood. The pinblock has one hole per string, or up to 240 holes, drilled in it.
4 The cast iron plate is made in a piano plate foundry. Match-plates are made of metal from the wood pattern designed by the engineer with top and bottom pieces to match. Sand molds are made from the match-plates, and these are used to cast the plate. Molten iron is poured through the molds and allowed to harden during the founding process (a controlled cooling process) to produce a plate weighing about 600 lb (272.4 kg). After the plate is cooled and removed from the molds, sand is blasted off the plate with steel grit. The plate is transported on overhead conveyors to a drill room where holes are drilled for the tuning pins, nosebolts, bolts to the frame, and hitch pins. The hitch pins are inserted next; then the casting imperfections are removed from the plate by grinding and drilling. Oils are also removed. The plate is hand-sanded and rubbed, primed, and painted.
5 The cast iron plate is suspended above its piano during the process of fitting. The plate will be lowered and raised in and out of the piano several times as the pinblock, seal against the rim, and the sound-board and bridges are fitted.
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