FUNCTION OF THE TUNING HEADS
Tuning the instrument.
INDICATION OF PROBLEMS WITH THE TUNING HEADS
Hard to turn; Turns without tuning guitar; Instrument won’t stay in tune.
WHAT TO LOOK FOR: The most common complaint I get as a repairperson is that the customer’s instrument won’t stay in tune. Matter of fact, that’s one of the main reasons for writing this booklet; to help you keep your instrument playing in tune! If there are tuning problems, many times the player thinks the tuning heads (also called machine heads or tuners) are “slipping”. Most of the time, this is not the case. If the instrument is going out of tune, there are usually other reasons. Under normal conditions the tuning heads work fine and need little care.
ADJUSTMENTS: 
CLOSED MACHINES…. the kind where you can’t see the gears, are lubricated and sealed at the factory and need no further maintenance. Often this type of machine has a small screw on the end of the button. This is used to change the amount of resistance between the gears, thus giving a stiffer feel to the tuner and holding the gears tighter. (See Fig. #1, left example) Do not over tighten this screw, a snug fit is best.
OPEN MACHINES…. the kind where you can see the gears on the back, may be lubricated a couple of times a year with petroleum jelly or cork grease (which is used on woodwind instruments). Place a small amount of one of these on the tip of a toothpick and work it between the gears. Be sure to wipe off all excess grease. Too much lubricant can and will hold dirt and fuzz which will cause the gears to wear. On open machine heads, check the small screw in the middle of the gear. (See Fig. #1, right example) Check these for looseness, but be aware this screw only holds the tuner together, it dose not make the tuner feel tighter as with the closed tuners mentioned above.
CAUTIONS: Do not over-tighten any of the screws on the tuning heads. If over-tightened, the gears of the tuning head will wear prematurely, therefore requiring replacement.