Locking tuners afford you a higher degree of tuning stability. As well as functioning exactly like a normal tuner, a locking tuner has an additional mechanism, typically in the form of a screw or a cap that clamps the string in place and prevents slippage. Schaller locking tuners have a thumbscrew at the rear that clamps the string in place inside the tuning head. The tuners will fit independently on most head stocks without the need for a mounting plate, save for customised or unusually shaped ones. A single pin mount holds the tuner steady when in use.
Remove existing tuners. Take off your strings using a string-winder for speed and then unscrew your tuners. Keep them as spares for any mods or projects you might have in the future. Brush away any dust from underneath the tuners and wipe the head stock clean.
Make a pencil mark on the headstock where you need to drill. Some guitars will have the right fittings others will require new holes; if your previous tuners are different sizes to the Schallers, drill new holes. Place the Schaller tuner in place and push it firmly into the headstock. Then place the tuner to one side. You will now have two small indentations on your headstock where the Schaller is screwed in. Mark the indentations with a pencil then drill a 10mm-wide hole if you don't already have one.
Screw the tuner into the existing hole in the headstock. The barrel of the tuner will slide through the hole left by the previous tuner.
Install the new nut. Attach the installation nut on to the partly secured tuner.
Screw the tuner in. Using a small screwdriver, screw in the screws that came with your tuners into the two 10mm holes previously drilled. Then screw in the mounting pin through the top of the tuner.
Put on a set of new strings. Thread the string through the barrel of the tuner as normal. When it is in tune, turn the 17mm thumbscrew to fix the string in place.
Adjust intonation. Once you've fitted all six tuners and the new strings, tune your guitar again. Plug into a chromatic tuner. Play each string open followed by the 12th fret. If there is a difference in tuner reading between the open and 12th fret octave note, adjust the intonation accordingly. Fix the intonation by adjusting the saddle forwards for high flat intonation and backwards for high intonation.
Don't drill any further in to the head stock than the length of the screw.
Ensure that you drill exactly where the indentations were made to avoid having to redrill.