A front rail pin is a metal pin that is inserted into the front rail. Its purpose is to catch and support the key when the key has been pressed. They are usually made of nickel plated steel, and are oval shaped. When the key is pressed the pin enters the front of the key in the mortise on the underside. The key is kept snug against the pin via the key bushings.
Front rails are drilled with pilot holes, then the pins are tapped into the wood. The pins are all equal size, mass, and are inserted at the same place relative to the key. The sharps or black keys, have their pins offset as the length of the key is shorter.
The front rail is a key component is setting the key dip of a piano. Felt punchings with a hole in the centre are added onto the front rail pin. This prevents knocking and clicking of the two wooden surfaces of the front rail and the key. Often, paper shims are added to adjust the key dip. This is important for correctly functioning action parts. They are larger in diameter than the smaller balance rail punchings.
Front rail pins can be polished, and lubricant such as Protek can be applied to help reduce friction between the pin and the key bushing. A common cause of keys sticking is a swollen key bushing that is stuck against the pin. Easing the keys can help this.
Side play is the amount of movement that the key exhibits when it is moved side to side. An effective way of reducing the amount of side play is to turn the front rail pin clockwise or anti-clockwise in order to increase the amount of pin that comes into contact with the bushing.
A similar, but smaller pin is found on the balance rail of the piano. This is called the balance rail pin.
