Tuning wrench

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T-shaped tuning wrench

A tuning wrench (also called a tuning lever or tuning hammer) is a specialized socket wrench used to tune string instruments such as the piano, harp, and hammer dulcimer, that have strings wrapped around tuning pins with square heads. Other string instruments do not require a tuning wrench because strings their tuning pins or pegs come with handles (as with the violin), or geared tuning machines (as with the guitar or banjo).

Tuning wrench sockets may be square shaped or 8-pointed star shaped, and are found in two basic sizes: a large size for pianos, and a smaller size for most other instruments. For pianos, there are some gradations of size, and several lengths are generally available, and unlike machine-screw sockets which have no taper, piano sockets have a slight taper, to fit tapered tuning pins. Tuning wrench sockets are often attached snugly to the handle with fine-gauge machine-screw threads, to provide a very firm, immobile joint; this is contrast to the square snap-on joints found in sockets used for machinery.

Unlike most socket wrenches, tuning wrenches usually have a comfortable wood or nylon handle. They are found in two basic shapes: L-shaped and T-shaped. L-shaped handles for pianos are available in several angles that are not quite right angles, provide greater leverage than T-shaped handles, and the angle provides clearance for the handle over adjacent pins, allowing a very short (and stiff) socket to be used. A short, stiff socket enables a better feel and control of the tiny movements of the tuning pin, within the pin-block. A T-shaped handle helps keep torque parallel to the shaft of the bolt. Some musicians feel that torque in other directions risks widening the hole around the bolt holding the string.