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8 - Wrest-pins / tuning pins

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The tuning pins in a piano are long and thin metal rods that hold the strings in place and allow the tuning of the strings. Each string of a piano is attached at one end to the plate (also known as the cast iron plate or frame) and at the other end to the pins located at the back of the piano and inserted into small holes, which is the vertical beam at the back of the piano. The strings are tightened or loosened by turning the tuning pins, which raise or lower the pitch of the string. The tuning pins are an essential component of the piano, as they keep the strings in the right tension and allow the instrument to be tuned to the desired frequency.


The first methods used were in the monochord, in which the string is fixed to a point and is put under tension by a movable weight. In bowed instruments, wooden tuning pins without threading are used. The first metallic tuning pins were used for the harpsichord. They were very thin, probably made of thick metal round bars, which were flattened with a hammer in order to be able to be inserted with a tuning key. Their diameter was about two or three mm. When the tension of the strings increased, it was necessary to increase the diameter of the tuning pins. Harpsichords, pianos, and similar instruments still have tuning pins with a thickness of about five mm, due to the weak tension of the strings. In table pianos, flat or rectangular headed tuning pins were used until the 19th century. The threading of the tuning pins was already introduced in the 18th century to increase friction. Modern pins are very strong.

Tuning pins quality must be produced in steel and must have a torsional strength of 80/90 kg/mm2. For multilayer soundboards, it is better to use nickel-plated pins. The pins are driven to a depth of 30mm into the wood, of which at least 24 mm should be in the actual multilayer. The exposed part of the pin should not exceed 11mm measured between the plate and the string attachment hole of the pin itself. The pins must rotate without noise and without particular twists. After the installation of the strings, their triple leveling and their triple tuning, there should be a resistance to the rotation of the pins not less than 1.4 kpm when rotated counterclockwise. The inclination of the pins in the soundboard should be between 92° and 96° degrees. The arrangement of the pins in the soundboard should be such as to ensure that the strings do not touch each other.

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