Removing a key’s threaded collar using a 10 mm nut driver.
With the strings removed, unscrew the mounting screws on the back of the headstock, then (if applicable) remove the threaded collar that surrounds the post with a 10 mm nut-driver. If your guitar has press-in bushings, I recommend leaving them in. Removing the bushings can damage the finish or wood surrounding the post hole.
When installing the new keys, insert the key into the hole, install the screw on the back of the headstock, and then finally tighten the threaded collar. Do not use an open wrench or adjustable wrench on the collar. The wrench can slip and butcher the nut or put a big ding in your headstock. A nut driver or deep-well socket lets you apply gentle downward pressure as you tighten the threads and this keeps the tool in place.
Don’t attempt to tighten a threaded collar or bushing with an adjustable crescent wrench—it can slip and mar the collar or headstock.
Caution! Be careful when tightening the screws and the collar. If you over-tighten the screws, you’ll strip the headstock wood. This damage can be repaired, but it requires gluing dowels into the headstock. If you over-tighten the collar, it will strip the threads and ruin the collar. Damage to the collar is irreversible, and you’ll have to buy another tuner.
Screwless keys. One more thing: Some tuning keys don’t attach to the headstock with screws. Instead, they have one or two alignment pins on the underside of the shell that insert into the back of the headstock. Check this carefully when you replace your keys and make sure you buy the correct style to fit your guitar.
Some tuners have one or two alignment pins instead of screws. Carefully check your guitar before buying replacement tuners to assure a correct match.