Kluson Lockhead MLG33N 3+3 Nickel Machine Heads A simple locking machine of highest quality! The slotted locking screw is tighened by a coin and presses on a little steel ball, which tightens the string softly. Compared with other lock tuners this machine head keeps its general function and also works without the locking mechanism very best! Drill hole 10mm. Gear ratio 1:18.