Machine Head - Varieties

Varieties

Normally, worm gears provide a gear ratio of 14:1. Versions with an 18:1 gear ratio also exist, trading better accuracy in fine tuning against slower initial string winding.

Several kinds of machine head apparatus exist:

• on classical guitars (with nylon strings), the worm gears are generally exposed; the strings are wound on the pins inside grooves in the head;
• on steel-string guitars, including "folk" acoustic guitars and electric guitars, the worm gears are generally placed in individual sealed enclosures with permanent lubrication, although budget models may have exposed gears fixed on plates housing a row of gears; several machine head placements are possible, depending on the shape of the headstock:
  • rectangular head, 2 rows of 3 pins (or 6 pins for 12-string guitars): found on most "Folk" and "Jazz" guitars and on Gibson Les Paul guitars;
  • a single diagonal row of 6 pins: found on Fender Telecaster and Stratocaster guitars;
  • one diagonal row of four pins and one diagonal row of two pins: found on Music Man guitars;
• on bass guitars, where string tension is extremely high, larger, heavier-duty machine heads than those used on guitars are used. Bass tuners generally feature larger knobs than guitar tuners as well; often these are distinctively shaped, and known as "elephant ears." Gear ratios of 20:1 are used often. Exposed gears are much more common in premium bass guitars than in six string non-bass instruments.

Since 1950s, guitar performance techniques evolved, and aggressive usage of tremolo arm became widespread. However, the original machine heads couldn't withstand the rigors of constant string tension changing, and strings got out of tune after using tremolo several times. Several manufacturers, including Grover and Floyd Rose, introduced a new design, commonly named locking machine heads nowadays: a machine head with additional mechanism to lock it in place and stabilize tuning while playing and using tremolo. However, such machine heads reached limited success, mostly because of their price: as of 2006, locking ones are about 50% more expensive than original. Many break strings when tension is increased while the mechanism is locked and later unlocked, which frequently happens in music stores.

Note that on some guitars, such as those with Floyd Rose bridge, string tuning may be also conducted using microtuning tuners located at guitar bridge. In this case, main machine heads at headstock may be missing entirely, as well as the headstock itself.

Likewise, 'headless' guitars and basses, notably those designed by Steinberger and their licensed imitations, such as the Hohner Jack Bass, and unlicensed imitations such as the Washburn Bantam, have the machine heads at the body end. Steinbergers and Hohners require specialist double-ball end strings, whereas the Washburn Bantam can take regular strings.