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The Belly

Strings, Tuning Pins, Pinblock, Soundboard and Bridges

Grand piano restorationThe “Belly” is what makes a piano heavy. Why? When all the strings are at their proper tension, tuned to A=440, a concert grand piano holds about 18 tons (9 mid size cars on a string) of pressure. The piano is engineered to handle this kind of stress for a very long time. The metal plate holds much of the tension, and on well built pianos, the stress is shared with beams built into a very hefty case.

When disassembling a piano, one must take great care in the measuring and removal of all original strings.

A pattern is taken of the bass strings (all of which are coiled) and custom made for each individual piano.
Piano Strings
The tenor strings to the treble are made of high quality steel, in different gauges.

The lower the note, the heavier (or thicker) the gauge. There is a specific pattern in which the strings are loosened for removal. If this pattern is not followed, it could crack the plate—problem that is as close to unsolvable as possible.
Strings are loosened according to a specific pattern
Another extremely important measurement is the position of the metal plate. Should this measurement be overlooked, and the plate is put back in a slightly different position, it will change the voice of the piano, sometimes drastically for the worse, forever.
Positioning of the metal plate affects the piano's voice.
After the strings and the plate are removed, the soundboard can be repaired or replaced as needed.
Repairing the soundboard
Soundboard repair is a viable option, only if the soundboard has retained its “crown” over the years. A simple illustration of crown is shown below:
Soundboard crown
A quality soundboard is made of solid spruce. Most soundboards will develop cracks in them due to humidity changes from year to year. This occurs in the best of pianos, and the worst of pianos.

You may have heard (probably from a new piano salesman) that if the soundboard is cracked, the piano is ready to throw away. This is a fable. The only crack that can send a piano to the junk heap is a crack in the PLATE. Even then, a cracked plate can be repaired, by the right person, using the right materials – but of all piano repairs, repairing a cracked plate is by far the most risky, due to the enormous tension from the strings. A cracked pinblock can be replaced, and a cracked soundboard can certainly be repaired or replaced.

We provide expert replacement of soundboards using state of the art equipment, duplicating precisely in manufacture and materials.

The crack in the soundboard is actually the least of the problems in repair, and is more cosmetic than anything. The most important aspect of soundboard repair is to be certain that the board is glued solid to the ribs.

There are many methods to accomplish soundboard repair. One of the faster and cheaper methods leaves metal screws buried in the soundboard forever. Our standards are higher. We use screws to clamp the board to the rib, and when the glue is dry, we remove the screws and glue wooden dowels, for the strongest bond possible. The crack is filled with a spruce shim, glued directly into the crack itself.

All soundboard repair takes place only after we have dried the board to accentuate the cracks, or any other problems it may have, and it is repaired in this dry state. Once the board absorbs humidity, theoretically, it will not cosmetically crack again – certainly it will never come loose from the ribs in our lifetime, under normal circumstances.

The board is then scraped – not stripped with harsh chemical strippers, which can have an adverse effect on the wood of the soundboard. It is then sanded and finished, along with the bridges being scraped of old dull finish to reveal the beautiful white maple.

Finish is applied to the soundboard to seal in all the tonal goodness, and enhance its longevity.

Oh, one more thing about the soundboard- The Decal. After the first coat of finish, we apply the decal. It is then sprayed with its final coats, to seal and protect it – keeping it beautiful forever.

After the plate is removed, it is cleaned and prepped. Preparing the plate for refinishing includes filling in any cosmetic problems it may have from the old paint, priming and sanding. It is then sprayed with our special “plate” gold, and 2-3 coats of gloss lacquer is applied over the gold to give it a beautiful luster, and visual depth.

And we love to “letter” the plate!

Now that the plate, soundboard and bridges are ready, let’s work on the pinblock.

The pinblock is the laminated piece of rock maple that holds the pins tight. It is located under the plate, in the front of the piano. Some pianos have an “exposed” pinblock, which means the plate does not cover the block at the tuning pins. Below is an example of an exposed pinblock:

On most pianos, the plate covers the pinblock, as shown below on an upright piano:
And with the plate removed:

Here is a pinblock with the plate upside down.

And with the plate removed.

Replacing the pinblock is essential for most restorations. It is rare that a 70 to 100 year old block has any life left in it. The block expands and contracts with humidity levels, like everything else made of wood. Eventually, the laminates begin to separate, the tuning pins get loose, and the piano no longer holds a tune.

Using a plank of Pinblock material, a duplicate is cut, fitted to the plate and the case, drilled and installed. This entire process is not only tedious; it must be done with the utmost care in every step.

As mentioned before, the positioning of these components is one of the most critical aspects of rebuilding. It takes precise craftsmanship and time to do this correctly.

Once the plate and the block are in position, and installed, the “understring” felts are put on to dress the plate. All these felts, and string braiding are installed not only for cosmetics, but also to mute unwanted vibrations and overtones.

After the plate is dressed, we string the piano. The string end is inserted into the tuning pin, and coiled. The coiled tuning pin is hammered into the pinblock – the tuning pins are slightly larger than the holes that we drill in the pinblock, insuring a tight fit for a lifetime.

Great care is taken to make the coils and pins uniform, not only for form but function as well.

After all the strings are installed, the piano is “chipped”. This is a rough tuning to A=440, bringing the strings close to their proper tension. After chipping, the dampers are installed. The dampers are the felts that mute the vibration of the string when you lift your finger off the key. This is really part of the action, but we have always included replacing the dampers in the rebuilding process with the principle in mind- new strings, new damper felts.

Once the dampers are installed and regulated, we are ready to install the action, and give the piano its final tunings.

After rebuilding, the piano will go out of tune very quickly. Why? The tension of the strings need to “equalize” between termination points. A termination point is any point that the string rests on the plate or the bridge. There can be up to 8 termination points on a string. Remember the bridges? We wanted to keep the bridges free of finish so that the string will slide smoothly across the bridge- every time you play a newly rebuilt piano, the strings slide just a little bit, and eventually settle to hold a tune.

I would love to discuss your piano with you, personally.  Fill out the form on the top right of this page or pick up the phone and play 1-800 ON A PIANO (662-7426) and lets work together to get your piano back into excellent playing condition.

Rebuilding and Regulating the Action

Refinishing the Case

Get an Estimate

For more detail on Rebuilding the Belly, click the links below:
Replace Pin Block
New Strings and Tuning Pins
Replace Bass Strings
Soundboard Repair- Reglue ribs to board
Bridge Repair


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