Restringing a piano commonly is part of rebuilding and not necessarily a maintenance item as with others string instruments. Piano strings can last for generations. Daily, I tune instruments that are 80 to 100 years old that still have the original strings. However, with performance or recording instruments, which have to be optimal at all times, it is common to restring as often as every ten years.
Why Do Pianos Have To Be Restrung?
Piano strings are made of piano wire, a high carbon refined grade of music wire, of various diameters. Each string is strung to a tension determined by the scale design of the instrument. Strings have bearing or pressure points at the hitch pin, bridge pins, agraffes/pressure bar, and tuning pins. It is at these points that the wire fatigues over time. As piano wire ages the point at which its ability to remain elastic decreases as the wire stiffens with age. When required tension begins to stretch the wire it’s acoustic properties are compromised. Excessive playing also will accelerate fatigue of the wire.
What Other Work Should Be Considered When Restringing a Piano?
Piano restringing is not an easy routine maintenance item as it is with other stringed instruments. It requires extensive works. When considering restringing it is important to evaluate the entire instrument for other structural deficiencies. If the bridges are cracking, the pin block is worn, and the soundboard is failing one must considering rebuilding the instrument in order to have a solid foundation upon which to string. Otherwise, there will be problems. In this case money and effort has been wasted on restringing.
Other items to consider are:
- Plate Refinishing
- Soundboard Repair
- Bridge Replacement
- Pinblock Replacement
- Damper Replacement
What Does Piano Restringing Involve?
Typically restringing includes:
- Damper Removal
- Recording the string scale
- String Removal
- Tuning Pin Extraction
- Bass string Duplication
- New String Installation
- New Damper Installation
The following pictures show the various steps involved in restringing grand piano.
Selecting the correct size tuning pin.
Tuning pins vary in length and diameter. I always use 2/0 (.282″) dia. pins when stringing a piano with a new pinblock. The length is determined by the thickness of the pinblock. Tuning pins are blued or plated steel with a fine thread allowing the pins to be extracted by turning. Tuning pins are hammered into a pre-drilled hole.
Testing torque to determine correct diameter of hole will determine drill bit size
Determining the correct resistance of tuning pins is critical. Depending on the type wrestplank material used to build the pinblock, the tuning pin hole is drilled to approximately .020″ tolerance. This image shows a test done by feel. A torque wrench can also be used by one not atuned to the feel of correct pin torque.
Drilling the Pin Block
Tuning pin holes are drilled within 24 hours of stringing to maintain consistency in pin torque and smooth movement. Notice how the drilling apparatus is at a fixed angle. This particular one is set at a 6 degree rake angle. A high helix polished flute drill bit is used with controlled feed speed.
Setting the Coil
Bending the becket is a critical first step in creating a quality coil. This is the point where the wire inserts into the tuning pin and is bent to begin the coil. A well-set becket and tightly packed coil assures string stability at the tuning pin. If coils are not set correctly tuning instability will occur.
Bending the Hitch
Most piano stringing scales involve a continuous wire for every two strings in the treble/tenor section. This means the wire is coiled onto a tuning pin, bent around the hitch pin and coiled again around another tuning pin. A proper hitch involves an accurate bend around the hitch pin with the string seated firmly against the plate. This is another point where precision renders stability.
Bass String Hitch
Unlike treble and tenor strings, bass strings are individual. One end is coiled on a tuning pin and the other attached to the hitch pin as illustrated.
Twisting Piano Bass Strings
Since bass strings have a copper wrapping to add mass without adding stiffness, the strings must be twisted to assure the wrap remains tight.
Aliquot Rail for Duplex Scale
The section of the string between the bridge and hitch pin is often set to be within the harmonic overtone series of the fundamental of the specific string. This is done by inserting a bearing point called an Aloquot. This image is from a Steinway piano that utilizes a duplex scale bar. Others use individual bars for each note. A duplex scale has the potential to add sympathetic harmonic overtones to enrich the sound.
Installing Bass Strings
Bass strings are unique for each piano. The original strings, specifications, or a pattern are sent to a string maker for new strings can be custom made. Each string is installed individually: attached to the hitch pin, coiled to a tuning pin, twisted and inserted into the pin block.
After the instrument is strung a rough chromatic tuning to standard pitch (A440) is done through a process called chipping. Since the action is not yet available the strings have to be plucked with a wood pick (not by hand to avoid tarnishing) in order to equalized tension across the scale. Once the action is installed the instrument then receives as many as five tunings over the remainder of time before delivery. Once delivered the instrument is allowed to set for approximately 10 days and is then retuned. A follow-up tuning schedule generally is: 3mo. /4mo. /6mo. and every six months after that. Not following such a schedule will not allow the instrument to stabilize. This can have life-long consequences.