Coming Together: Fitting The Soundboard & Plate to the Pianos Rim
September 9th, 2009
Workmanship and Materials
Rim: The Steinway System
All Steinway grand pianos are built upon rims made entirely from straight-grain hard rock maple. The number of laminations varies according to model: 12 for the Model S, 13 for the M, 14 for the O, 16 for the B and 18 for the D. Each lamination is three sixteenths of an inch thick, and each is positioned so that the grain is set horizontally. Horizontal setting, rather than the cross-graining (the technique for plywood) used by some makers of grands, improves tonal projection by some 47%.
All Steinway grand piano rims are continuously bent in presses designed and built by Steinway. Together, the inner and outer rims form one united rim. Modern high-frequency gluing welds together the laminations.
After being glued the rims are removed from the presses, chalk-dated and stored upright in a conditioning room. There they relax from the tremendous shock of being bent. Piano rims remain in the conditioning room between 10 and 16 weeks, depending on thickness and size. The room’s temperature is set at 85 degrees Fahrenheit; the relative humidity is 45%.
In terms of design, materials, and workmanship, the Steinway System of rim-bending maintains ultra-high overall string tension, as well as down-bearing and side-bearing, almost indefinitely.
This method of rim-bending was invented by C.F. Theodore Steinway. It became U.S. Patent no. 229298 on June 22, 1880. The original patented process is strictly adhered to today, over 112 years later.
FITTING THE SOUNDBOARD AND PLATE TO THE RIM REQUIRES 15 OPERATIONS
1. Creating a fit that supports up to 10 tons of string tension involves fitting the front edge of the plate flange against the back edge of the wrestplank and hoisting the plate up and down repeatedly, until the fit is perfect.
2. Craftspeople use wooden scale patterns to determine precise rib locations. They hand-notch the top of the inner rim so that it accepts rib ends of the “double-crowned” relaxed soundboard.
3. The soundboard is custom cut and fit into the case. Its edge must fit snugly against the inside of the outer rim to support the important crown.
4. With the soundboard positioned on top of the inner rim, the plate is lowered into the case to take string down-bearing. Bridges are marked every three inches with a triangular wood file to determine proper bridge height.
5. To give the craftsperson access to the soundboard, the plate is again hoisted above the case.
6. The soundboard is removed from the case and secured to its proper scale “belly board” for custom fitting.
7. Tops of bridges are planed to coincide with the plate for precise bearing…Tops of bridges are brushed with a black graphitic paint…Perforated steel templates are affixed to tops of bridges…Bridge pin holes are marked with a pointed steel punch through each template perforation…Templates are removed and bridge pin holes are hand-drilled…Bridges are hand-notched with a sharp chisel…Bridge pins are driven to prper depth.
8. Soundboard is placed in a conditioning room set at 90 degrees Fahrenheit and 40% relative humidity. For ten weeks it “relaxes” from the shock of double-crowning.
9. Soundboard is removed from conditioning room and hand-brushed with heavy-duty sealing varnish.
10. Soundboard is positioned in the case and permanently glued to top of inner rim.
11. Holes are drilled through the soundboard, into the top of the inner rim, to receive plate anchoring screws.
12. Two holes are drilled, one on each side of plate screw holes, to accept 7/16 inch (diameter) by 2 1/4 inch (length) maple dowels (horizontally scored for glue channels) upon which the plate will be mounted.
13. Plate is lowered into the case to rest on top of the maple dowels, which range in number from 20 in Model S to 28 in Model D. Bearing is taken.
14. The pianos plate will be hoisted up and down, numerous times, to permit shaving off tops of the maple dowels for precise plate height, thus, perfect bearing.
15. The plate will be lowered into the case, for the final time, to rest on the maple dowel tops followed by the application of nickeled steel wood screws which anchor the plate into its case.
These 15 steps for marrying the soundboard and plate to the case take eight weeks for a Model S, ten weeks for a Model D.
REMEMBER: THE TIME REQUIRED TO COMPLETE A STEINWAY GRAND, FROM DRYING THE WOOD TO FINAL INSPECTION, IS 12 MONTHS.
GRAND CASE: The grand case includes the united rim, cornice, wrestplank, keybed, crossblock, front rail, braces and backbottom.
When Steinway’s rim-bending patent expired years ago other grand piano makers began to employ the method. Over the years, however, nearly every manufacturer discontinued the production of a single united rim in favor of two separate rims (inner and outer). The reason others choose the two-rim system – it’s much cheaper.