Fig 6Tuning pin and pinblockDrag to turn · space to listenpin 0.00° · 89.7 kgf · C6 in tune
The lever, and the two needles that answer itPin, plate, agraffe, bridge and hitch pinThe C6 string: three turns round the pinA tuning pin holds a string by friction alone: 0.95 mm of steel wire at 89.7 kgf pulls round the pin with 3.5 N·m, and seven cross-laminated plies of maple grip the pin with about 14 N·m, so the tuner pulls about 70 N at the end of a 20 cm lever to move it. Each degree of turn winds 0.069 mm of wire on to the pin. Spread over the string's 328 mm, that adds 30.0 N of tension, and the pitch rises by 29 cents, nearly a third of a semitone. Tuners therefore move pins by hundredths of a degree, listening for the beats between the string and a reference. Space plays both, so you can hear the beats slow down as the pin comes into tune.