Quick read: Most locking-tuner installations go smoothly: pull the old tuners, drop in the new ones, line up the screw holes, drive the mounting screws, done in 30 minutes. The job stretches to two hours when one of three things is true. First: your headstock has 10mm tuner-post holes and your new tuners need 9.5mm (most modern Strats, almost all Teles, every Schaller and Sperzel). You need step-down bushing adapters. Second: your new tuners have screw mounts that don't line up with the existing screw holes, which is the common case when upgrading from vintage Kluson-style tuners with single press-fit pins to modern Hipshot or Schaller tuners with two-screw mounts. You drill new pilot holes. Third: your headstock is one of the soft maples that splits if you drive a screw without a pilot. Always drill a pilot. The actual work is straightforward — a Phillips screwdriver, a 3/32″ drill bit, a hand drill, and a feeler gauge. The trouble comes from skipping the diagnostic steps that tell you which of these three situations you're in. Read the headstock before you reach for the screwdriver.
The slip-test post we ran the other week answered which locking tuner to buy. The follow-up question every comment thread asked was "how do I install them." The manufacturer instructions are short and terse, and most of the YouTube tutorials cover the easy case — Strat headstock, screws line up, drop them in, you're done — without mentioning what to do when your headstock isn't that easy.
This is the long version. The job is still a 30-minute job when everything fits. It becomes a two-hour job when it doesn't, and most of the two hours is figuring out what doesn't fit. Here's how to figure it out first.
What You Need
- The new tuners (six in line, or three-and-three, depending on your guitar)
- A Phillips #1 screwdriver — hand-held, not powered (powered drivers strip screws)
- A 3/32″ drill bit (some headstocks need 5/64″ — measure the screw shank first)
- A hand drill, ideally one with a clutch
- A small ruler or calipers, for measuring the tuner-post hole diameter
- Step-down bushing adapters, ONLY if your post holes are 10mm and your tuners need 9.5mm
- Painter's tape
- A feeler gauge (any thickness; you're using it as a depth stop)
- A small bowl to keep the new tuner washers and bushings from rolling off the bench
That's it. No router, no specialty press, no luthier-only tools. The whole job runs on hand tools.
Step One: Read the Headstock Before You Start
This is the step nobody does and most of the wasted hours come from skipping it.
Pull one of the old tuners. Just one. Measure the post hole with calipers or a ruler — modern hardware stores have plastic calipers for $8 if you don't own a real pair. The hole is one of three sizes:
- 10mm — common on older American Fenders, almost all vintage-style Teles, and most pre-2010 Squiers
- 9.5mm — common on modern American Fenders, modern Squiers, and most import guitars
- 8.4mm (about 11/32″) — common on vintage Gibsons and Kluson-style sets
Then look at the screw mount on the old tuner. Count the mounting screws. Note their position relative to the tuner shaft. Take a photo of the back of the headstock with the old tuner still on it; you'll thank yourself in ten minutes.
Now look at the new tuners. The post-hole size is on the box or in the spec sheet. Hipshot Grip-Locks are 10mm by default with a 9.5mm bushing-adapter set sold separately. Sperzel Trim-Loks are 9.5mm. Schaller M6 Locking are 10mm. Gotoh SG381 MGTs come in both sizes — read the model number carefully.
If your headstock post holes match the new tuners' post size, you have an easy install. If they don't, you need bushing adapters or a luthier with a hand reamer. Almost nobody needs a reamer; almost everybody can use bushing adapters.
The same compatibility check applies to the screw mounts. Most modern locking tuners have either a single locator pin, a single mounting screw, or two mounting screws. The Schaller M6 has a single locating pin. Hipshot Grip-Locks have a single screw on a curved tab. Sperzel Trim-Loks have a single screw on a flat back. If your old tuners had a different mounting pattern, you'll be drilling new pilot holes for the new screws. The old screw holes will sit there empty under the new tuner backplate, which is normal and invisible from the front.
Step Two: Remove the Old Tuners
Slack the strings until they're loose, then cut them. Don't try to save a string set during a tuner install. Throw the strings out.
Use the Phillips #1 to back out the screws on each tuner. Hand-driven, slow. If a screw is corroded or stuck, put a drop of penetrating oil on it and wait ten minutes. Don't force it; a stripped screw head turns a 30-minute job into a two-hour job all by itself.
With the screws out, the tuner body lifts off the back. The bushing or press-fit washer on the front of the headstock comes out next. For press-fit Kluson-style bushings, push gently from the back with a thin dowel — a pencil's flat end works. For threaded bushings (modern Fender, most imports), unscrew them from the front; they usually back out with finger pressure once the tuner body is removed.
Stack the old tuners in their original order. Put the washers and bushings in your small bowl. If you ever sell this guitar, the original tuners go with it — keep them.
Step Three: Test-Fit the New Tuners Before You Drill Anything
This is the step where two-hour jobs turn back into 30-minute jobs.
Drop a new bushing into the front of the headstock without screwing it in. Push it down with your finger. Does it sit flush with the front surface of the headstock? If yes, the post hole is the right size. If no, two things can be wrong: the post hole is bigger than the bushing (you need bushing adapters or a luthier) or the post hole is smaller than the bushing (you need to ream the hole, which means a luthier).
If the post hole is too big, install the step-down bushing adapter first. Hipshot sells these as "conversion bushings" — a brass sleeve that drops into a 10mm hole and accepts the Hipshot 9.5mm bushing. Schaller and Gotoh sell similar parts. The adapter installs with finger pressure; no glue, no press, no tools.
With the bushing installed (or the adapter and bushing both installed), drop a tuner body into place from the back. The post goes through the headstock hole and emerges from the front through the bushing. The tuner's back plate should sit flush against the back of the headstock with no rocking. If it rocks, the bushing isn't seated correctly — pull everything and re-check.
Now check the screw alignment. Hold the tuner body in place from the back and look at where the mounting screw or screws need to land. Mark the screw position with a pencil — a single small dot is enough. Do this for all six (or three) tuners before you drill anything. Keep the tuner bodies in alignment with each other; the tuner posts should form a perfectly straight line down the headstock when viewed from the front.
If the old screw holes line up with your pencil marks, you don't need to drill new pilots. Drive the screws and you're done.
If the old screw holes are within 1mm of your pencil marks, you have a decision: drill new pilots and let the old holes sit empty, or use the old holes and accept that the tuners will be very slightly off-axis. I'd drill the new pilots. The old holes will be hidden under the tuner backplate.
If the old screw holes are 2mm or more off, drill new pilots and don't think about it.
Step Four: Drill the Pilot Holes (When Needed)
The pilot hole diameter is one size smaller than the screw shank. For most locking-tuner mounting screws, that's 3/32″ (about 2.4mm). Some smaller screws — Schaller M6 mini screws, for example — want 5/64″ (2mm). Measure the screw shank with calipers; the pilot bit should be 70-80% of the shank's outer diameter.
The depth of the pilot hole matters. Too shallow and the screw will split the wood. Too deep and the screw won't grip. The right depth is about 1mm less than the screw length. For a 12mm tuner screw, drill a 10-11mm pilot.
Use the feeler gauge as a depth stop. Wrap a strip of painter's tape around the drill bit at the desired depth, then drill until the tape touches the headstock surface. Stop before you punch through.
Drill straight in, perpendicular to the headstock surface. A drill that wanders sideways will misalign the screw and the tuner backplate will sit at an angle. If your hand is shaky, use a small drill guide — a block of wood with a perpendicular hole — to keep the bit straight.
Don't skip the pilot. I have rebuilt enough cheap guitars with cracked headstocks to know what happens when somebody drives a self-tapping screw into untreated maple without a pilot. The wood splits along the grain, the crack runs into the headstock face, and the guitar needs a luthier visit that costs more than the locking tuners did. The pilot hole prevents this completely. It takes thirty seconds. Do it.
Step Five: Drive the Screws
Hand-driven, Phillips #1, slow. The screws should turn smoothly with light pressure for the first three-quarters of their length, then resist as the head reaches the tuner backplate. Stop the moment the head sits flush against the backplate. Do not over-torque.
A stripped screw head means you used a power driver, or the Phillips bit was the wrong size, or you drove the screw at an angle. All three are recoverable but annoying. The fix is to back out the stripped screw with locking pliers, clean the hole with a slightly larger drill bit, fill the hole with a sliver of toothpick and wood glue, let it dry overnight, and re-drill the pilot the next morning. This is why hand tools are better here. Hand tools don't strip screws unless you let them.
Move down the line — bass side to treble side, or treble side to bass — and install each tuner in sequence. Don't fully tighten any screw until all six tuners are seated. Then go back and snug each screw to flush.
Step Six: Check the Front Alignment
Look at the headstock from the front. The tuner posts should form a straight line (for in-line headstocks) or two parallel rows of three (for three-and-three headstocks). If one post sits visibly higher or lower than its neighbors, the bushing isn't seated, the back washer is missing, or the screw is over-torqued and pulling the tuner body off-axis.
The fix depends on the cause. A reseated bushing solves the first problem (pull the tuner, push the bushing down with finger pressure, re-install). A missing back washer solves the second (find the washer in your small bowl, it rolled). An over-torqued screw solves the third (back the screw off a quarter-turn).
Step Seven: String Up and Stretch
Restring with the gauge you normally use. The locking mechanism on the new tuners works one of three ways depending on brand:
- Hipshot Grip-Lock: Thread the string through the post hole, leave 1.5″ of slack past the post, turn the thumbscrew clockwise on the back of the tuner to clamp the string, wind once and tune up.
- Sperzel Trim-Lok: Thread the string through the post hole, pull tight, turn the locking knob on the back, no winding required.
- Schaller M6 Locking: Same as Sperzel — thread, pull tight, lock, tune.
- Gotoh SG381 MGT: Same as Hipshot — thread, leave some slack, lock, wind once.
All four lock against the string with a knurled knob on the back of the tuner. The knob should be finger-tight, not wrench-tight. Over-tightening the locking knob can deform the string and reduce tuning stability rather than increase it.
Stretch each string by pulling it straight up off the fretboard at the 12th fret about an inch, three or four times, then re-tune. Locking tuners settle in faster than friction-style tuners because the string-to-post connection isn't slipping, but new strings still stretch from their internal coil tension. Five or six tuning passes is normal for the first hour.
What to Do If It Doesn't Feel Right
The most common installation problems and what to do:
- Tuner buzzes or rattles when the string is plucked: The bushing isn't fully seated, or the back washer is loose. Pull the tuner, reseat both, reinstall.
- String slips at the tuner post: The locking knob isn't tight enough, or the string was wound the wrong direction. Most locking tuners want one full wrap around the post before the string heads to the nut.
- Tuning stability is worse than before: Almost always a nut problem, not a tuner problem. If the nut slots are too tight or too rough, the string binds in the nut and the tuner can't keep up. Lubricate the nut slots with graphite from a pencil tip, or have a luthier file the slots properly.
- Tuner won't sit flush: A screw is over-torqued, or the back of the tuner has a high spot you didn't notice. Loosen everything, check the tuner-body underside for a manufacturing burr, and seat it again.
The job goes smoothly when you read the headstock first. The job goes sideways when you start drilling before you've test-fit. Most of the "two-hour locking tuner installations" I've seen on forum threads were caused by skipping the test-fit and learning halfway through that the bushings didn't match the headstock holes.
It just works when you check first.
The work itself is straightforward. The trick is reading the situation before you cut, drill, or screw anything. Measure the post-hole diameter. Compare to the new tuner's spec. Test-fit before you drill. Drill a pilot before every screw. Drive screws by hand, not by power tool. The two-hour installations come from skipping these steps; the 30-minute installations come from doing them in order. Most everything around guitar maintenance works that way.
