Top techs share their tips, tweaks, and onstage product development for brand-spankin’-new guitars.
Music styles have changed over the decades, and have generally intensified to a point where the rigors of performing live have become a contact sport. The hallmark of rock music has always been its over-the-top, live-presentation muscle, but as concert and club shows gained theatric power, sometimes the instruments weren’t up to the task. So, I decided to ask a couple high-profile techs about the state of the guitar on the road.
Mike Hickey is a veteran of decades of rock ’n’ roll, both as a performer and a technician. Most recently, he’s been Joe Bonamassa’s right-hand man onstage. Known for keeping Bonamassa’s arsenal of vintage guitars in shape, I asked him about his experience with newer guitars on the road. Hickey said, “I find they often need more truss-rod adjustments on a regular basis. This is most likely due to the newer wood used, which hasn’t had the last 50-plus-years to stabilize like the old-growth wood of the vintage guitars.” This is an interesting point that doesn’t get discussed much, as the emphasis on “old wood” is its supposedly superior tone qualities. When pushed about the quality of modern hardware, Hickey pointed out that vintage instruments are worn in and less likely to have problems. “Another generalized repair that comes up with new instruments is needing to file the bridge saddles to prevent string breakage,” he said.
Tuning stability is always important, both live and in the studio. In fact, it might be the tech’s most important job. So how does Hickey make certain his boss gets a guitar that’s in tune when he hands it off? “Lately, I have noticed with split-shaft posts on Fender-type instruments that I am getting some slipping on the 2nd and 1st strings,” he said. “This happens when I do the traditional loading of the strings into the center hole of the split shaft. To combat this, I thread the 2nd and 1st strings around the post as if it was a standard-style non-split shaft.” In the same way that new tuners and bridges might present problems with sharp edges, Hickey reasons that new nut slots need filing and smoothing since they’re not always fully tested at the factory. “We also lubricate the passage of the strings at that point,” he says.
When I asked if there’s a weak link on guitars in general, Hickey pointed to the break angle of strings on wraparound bridges and tailpieces. “I add an additional ball end on the strings to keep the main part of the string at the break point on the back of the tailpiece,” he revealed.
According to Hickey, the control pots are one place where new guitars can outshine an old one. “Sometimes we need to spray some cleaner into the potentiometers if we have a vintage guitar that has been sitting for a while. Not much can be done except to soldier on and get through the song with a bit of crackle! Sometimes you may see Joe whacking the knobs on his ES-335 while looking over to me laughing during a show!”
Drew Foppe’s resume is as varied as they come. He’s provided his services for artists as diverse as the Smashing Pumpkins, the Deftones, and Shakira. I posed the same question about new guitars to him, and he revealed similar thoughts to Hickey’s. “I usually end up improving on guitars right off the store wall or shipped out directly from a factory,” he says. “Most of the time, all that is required is a simple truss-rod and intonation adjustment.”
Although frets are one of the most important contributions to a guitar’s feel, Foppe isn’t always impressed. “I’ve been finding more and more guitars needing fretwork right out of the box.” Tuning issues are also a point of contention for Foppe. “First thing is you need a guitar that stays in tune. There are some companies that use garbage hardware that makes it hard to keep their guitars in tune, but it also helps keep their price point down. So, I get it, but some of it just isn’t made to last more than a couple shows.”
Like Hickey, Foppe isn’t a fan of factory spec nuts. “Second thing I check is the nut,” he says. “If a guitar ships with a plastic nut, I like to replace it immediately with a bone nut.” One bonus about a new factory-made guitar is that modifications aren’t going to necessarily devalue it. “Of course, you are never going to get a Les Paul to sound like a Strat, and vice-versa,” Foppe concludes, “but people still try. If you are limited to only having one or two guitars on stage, you can coil-tap humbuckers, wire pickups in series/parallel, or even create different pickup combinations.” In the end, Foppe concedes that the boss is always right. “Either way, you have to make any and all necessary adjustments to every instrument to the exact specs of what the artist wants.”
Fig. 1. A clean, well-condition fretboard just begs to be played.
Learn how to clean and condition your guitar and discover why it’s crucial to stay on top of such routine maintenance.
The proper cleaning and conditioning of your instrument is critical to its health. Over the years, I've seen many extreme cases of guitars that were permanently damaged from neglect. Without proper care, a guitar will lose value and eventually become unplayable. However, it's not difficult to clean and condition a guitar—it simply takes a little time and effort. And that's a worthy investment: Keeping your instrument in top condition will save you a lot of money in future repairs.
Fig. 2. Not only does fretboard gunk look unattractive, over time it can damage your instrument.
As we play, dead skin cells, sweat, and dirt build up on the fretboard and collect around the frets. Not only is this unattractive (Fig. 2), but the moisture, acids, and salts in sweat cause the wood around the frets to deteriorate. This can cause dry rot in the fretboard, which results in loose frets and very expensive repairs.
Fig. 3. These frets have become corroded through neglect.
I can always tell if a fretboard hasn't been conditioned when I examine the frets. This is especially noticeable when I'm doing a refret. After I remove the old frets, I can see nasty gunk on the tangs and green corrosion all over the fret wire (Fig. 3).
Fig. 4. If you don't clean and condition your fretboard, it may crack.
Cracks are another terrifying byproduct of not conditioning your fretboard (Fig. 4). When sweat evaporates, it can dry out the fretboard and cause it to crack.
Fig. 5. If they're not cleaned regularly, pickups, potentiometers, and switches can become corroded by the salts and acids in sweat.
A guitar's electronics can also suffer from dead skin cells and sweat. When acids and salts build up on a pickup, they can corrode the coils and magnets and cause the pickup to fail. These corrosive materials have the same effect on potentiometers and switches (Fig. 5).
Many string and accessory manufacturers offer conditioners for your guitar. But be aware that most of these products, including lemon oil, contain harmful chemicals and solvents that will damage your guitar's wood and finish. Avoid anything that contains d-Limonene, alcohol, or silicone.
Derived from oil extracted from citrus rind, d-Limonene contains natural acids. These acids can act as a solvent and break down finishes and cause the wood around the frets to deteriorate. Alcohol dries out the fretboard, bridge, and other unfinished wood, and can cause cloudiness in certain types of finish. Silicone prevents the wood from breathing and can cause the finish on your guitar to become hazy. It's also very difficult to remove.
Fig. 6. When wood isn't sufficiently humidified, it can dry out and crack. This guitar back has seen better days.
Controlling humidity is another important aspect of guitar care. When a guitar gets too dry, the wood cracks (Fig. 6). Conditioning wood certainly helps prevent it from cracking, but it's also a good idea to use a humidifier. New guitars tend to be more prone to humidity cracks than older instruments. Here's why: Most older or vintage guitars were made from air-dried wood. This wood was dried out over several decades, and during this process any pieces that cracked were culled out. The older harvested wood gets, the more stable it becomes, but it's a lengthy, painstaking way to dry wood. Modern guitars are primarily made from kiln-dried wood. Kiln drying is designed to speed up the aging process, but only time can truly age a piece of wood. Guitars made from kiln-dried wood are more susceptible to changes temperature and humidity. Maintaining a guitar-friendly humidity level helps prevent wood from cracking, and we'll discuss how to do this in a moment.
Cleaning and conditioning the fretboard. We'll start by cleaning the fretboard, and the first step here is to remove the strings. Yes, all of them! People often say, “Won't removing all the strings at the same time damage the neck?" The fact is, it won't. Wood has an excellent memory, so you don't have to worry about removing all the strings to service your fretboard. Luthiers do it all the time.
There are several ways to clean a fretboard, and one approach is to use 0000 steel wool. This works great, especially when you want to make your frets shine, but it makes a big mess. Caution: Do not use steel wool on a maple fretboard that has a glossy finish. Rubbing steel wool on any finish will make it hazy.
If you decide to use steel wool, use only 0000 grade. This is the finest steel wool and will not damage the fretboard or frets. If you're cleaning an electric guitar (or an acoustic with a magnetic soundhole pickup), cover the pickups with painter's tape to prevent the steel fibers from collecting around the pole pieces. These very fine steel fibers can cause a pickup to corrode, and they also cause noise if they contact the strings.
Fig. 7. If you opt to clean your fretboard and polish its frets with 0000 steel wool, remember to vacuum up the fibers that inevitably shed during this procedure.
Apply a fretboard conditioner to the fretboard and gently rub the conditioner into the wood with the steel wool pad, turning it frequently. Move across the fretboard, cleaning the wood between the frets, and then work the pad along the side of each fret. Once the fretboard is clean, run the pad up and down along the top of the frets to polish them.
After cleaning the fretboard with steel wool, use a vacuum to carefully remove the steel fibers that inevitably shed from the pad (Fig. 7). Avoid getting the fibers on the guitar's finish, as they can scratch it.
My preferred method for cleaning the fretboard is to use an old toothbrush and Planet Waves Hydrate, a type of fretboard conditioner. This approach is less messy than using steel wool, but it's important to note that Hydrate is only for dark fretboards—don't use it on maple 'boards.
Fig. 8. An alternative to steel wool: Clean the wood with a toothbrush and fretboard conditioner.
I like using a toothbrush because you can scrub all you want without damaging the wood or the frets. Simply spray Hydrate onto your fretboard and work it into the wood and around the frets with the toothbrush bristles (Fig. 8). Once the gunk is loosened, wipe it off with a paper towel. Also be sure you wipe off any excess conditioner to prevent it from coating the strings.
But the toothbrush technique won't polish the frets. If you're not too keen on using 0000 steel wool to do this (and I don't blame you), Planet Waves makes a product called the Fret Polishing System. Basically, it's super-fine polishing paper that's packaged with a protective stiff paper template that covers the wood while exposing the fretwire. The template fits medium or jumbo frets and you can use the kit on maple or dark fretboards.
Fig. 9. Planet Waves' Fret Polishing System includes super-fine abrasive paper and a guard to protect the wood.
Simply lay the template over the fretwire and polish the frets until they glisten (Fig. 9). The kit works great and there is little mess to clean up. But even with this system, you'll want to vacuum the residue off the neck left by the polishing paper.
Fig. 10. Like the fretboard, an acoustic guitar's bridge needs to be cleaned and conditioned.
Cleaning and conditioning a bridge. It's very simple to clean and condition the bridge on an acoustic guitar. Remove the bridge saddle and then scrub the bridge with a toothbrush and conditioner (Fig. 10). Use cotton swabs to clean inside the saddle slot. When the gunk is cleaned off, wipe down the bridge with a paper towel. That's it!
Fig. 11. Filth can build up on a bridge and its saddles. When hardware gets this dirty and rusty, you'll need to disassemble and clean it with WD-40 or 3-in-One oil.
Cleaning the hardware. Sweat is a big enemy of hardware because its acids and salts corrode the metal plating and attract dirt that clogs up any moving parts. In extreme cases, a guitar's bridge (Fig. 11) and tuning keys (Fig. 12) can begin to rust. Cleaning these important mechanisms keeps them looking good and functioning at their best.
Fig. 12. If left on metal hardware, sweat can eat right into the plating and cause rust.
For cleaning metal hardware, I've had success with 3-in-One oil and WD-40. Remember that these products are only safe on metal, so avoid getting them on the fretboard or finish. I typically remove the hardware to clean it with an old toothbrush and then carefully wipe it off before reinstalling.
Cleaning the finish. When cleaning your guitar's finish, avoid furniture polishes like Pledge, which contains lemon oil, or products that contain d-Limonene, alcohol, solvents, or silicone. All of these will damage the finish over time. Sweat is another finish-eater because it causes lacquer to soften and break down.
Water actually works well to clean a guitar finish. Use a slightly damp micro-fiber cloth to wipe away dust and grime, and rinse the cloth frequently to remove any debris. As for a good polish, I only use pure carnauba wax, which is safe for most finishes.
The Issues
Before we discuss how to clean and condition a guitar, it's important to understand where the potential problems lie and why we need to address them.
Two important components to clean, condition, and humidify are the fretboard and bridge. This is crucial because they are typically made of unfinished or untreated wood. Maple fretboards are an exception because they have some type of finish and therefore just need to be cleaned, but not conditioned. Rosewood and ebony fretboards and bridges must be cleaned and conditioned to prevent sweat and dirt from damaging the wood. A clean fretboard not only looks great (Fig. 1), but it feels great under your fingertips.
Fig. 2. Not only does fretboard gunk look unattractive, over time it can damage your instrument.
As we play, dead skin cells, sweat, and dirt build up on the fretboard and collect around the frets. Not only is this unattractive (Fig. 2), but the moisture, acids, and salts in sweat cause the wood around the frets to deteriorate. This can cause dry rot in the fretboard, which results in loose frets and very expensive repairs.
Fig. 3. These frets have become corroded through neglect.
I can always tell if a fretboard hasn't been conditioned when I examine the frets. This is especially noticeable when I'm doing a refret. After I remove the old frets, I can see nasty gunk on the tangs and green corrosion all over the fret wire (Fig. 3).
Fig. 4. If you don't clean and condition your fretboard, it may crack.
Cracks are another terrifying byproduct of not conditioning your fretboard (Fig. 4). When sweat evaporates, it can dry out the fretboard and cause it to crack.
Fig. 5. If they're not cleaned regularly, pickups, potentiometers, and switches can become corroded by the salts and acids in sweat.
A guitar's electronics can also suffer from dead skin cells and sweat. When acids and salts build up on a pickup, they can corrode the coils and magnets and cause the pickup to fail. These corrosive materials have the same effect on potentiometers and switches (Fig. 5).
Many string and accessory manufacturers offer conditioners for your guitar. But be aware that most of these products, including lemon oil, contain harmful chemicals and solvents that will damage your guitar's wood and finish. Avoid anything that contains d-Limonene, alcohol, or silicone.
Derived from oil extracted from citrus rind, d-Limonene contains natural acids. These acids can act as a solvent and break down finishes and cause the wood around the frets to deteriorate. Alcohol dries out the fretboard, bridge, and other unfinished wood, and can cause cloudiness in certain types of finish. Silicone prevents the wood from breathing and can cause the finish on your guitar to become hazy. It's also very difficult to remove.
Fig. 6. When wood isn't sufficiently humidified, it can dry out and crack. This guitar back has seen better days.
Controlling humidity is another important aspect of guitar care. When a guitar gets too dry, the wood cracks (Fig. 6). Conditioning wood certainly helps prevent it from cracking, but it's also a good idea to use a humidifier. New guitars tend to be more prone to humidity cracks than older instruments. Here's why: Most older or vintage guitars were made from air-dried wood. This wood was dried out over several decades, and during this process any pieces that cracked were culled out. The older harvested wood gets, the more stable it becomes, but it's a lengthy, painstaking way to dry wood. Modern guitars are primarily made from kiln-dried wood. Kiln drying is designed to speed up the aging process, but only time can truly age a piece of wood. Guitars made from kiln-dried wood are more susceptible to changes temperature and humidity. Maintaining a guitar-friendly humidity level helps prevent wood from cracking, and we'll discuss how to do this in a moment.
Cleaning and Conditioning the Fretboard.
We'll start by cleaning the fretboard, and the first step here is to remove the strings. Yes, all of them! People often say, "Won't removing all the strings at the same time damage the neck?" The fact is, it won't. Wood has an excellent memory, so you don't have to worry about removing all the strings to service your fretboard. Luthiers do it all the time.
There are several ways to clean a fretboard, and one approach is to use 0000 steel wool. This works great, especially when you want to make your frets shine, but it makes a big mess. Caution: Do not use steel wool on a maple fretboard that has a glossy finish. Rubbing steel wool on any finish will make it hazy.
If you decide to use steel wool, use only 0000 grade. This is the finest steel wool and will not damage the fretboard or frets. If you're cleaning an electric guitar (or an acoustic with a magnetic soundhole pickup), cover the pickups with painter's tape to prevent the steel fibers from collecting around the pole pieces. These very fine steel fibers can cause a pickup to corrode, and they also cause noise if they contact the strings.
Fig. 7. If you opt to clean your fretboard and polish its frets with 0000 steel wool, remember to vacuum up the fibers that inevitably shed during this procedure.
Apply a fretboard conditioner to the fretboard and gently rub the conditioner into the wood with the steel wool pad, turning it frequently. Move across the fretboard, cleaning the wood between the frets, and then work the pad along the side of each fret. Once the fretboard is clean, run the pad up and down along the top of the frets to polish them.
After cleaning the fretboard with steel wool, use a vacuum to carefully remove the steel fibers that inevitably shed from the pad (Fig. 7). Avoid getting the fibers on the guitar's finish, as they can scratch it.
My preferred method for cleaning the fretboard is to use an old toothbrush and Planet Waves Hydrate, a type of fretboard conditioner. This approach is less messy than using steel wool, but it's important to note that Hydrate is only for dark fretboards—don't use it on maple 'boards.
I like using a toothbrush because you can scrub all you want without damaging the wood or the frets. Simply spray Hydrate onto your fretboard and work it into the wood and around the frets with the toothbrush bristles (Fig. 8). Once the gunk is loosened, wipe it off with a paper towel. Also be sure you wipe off any excess conditioner to prevent it from coating the strings.
But the toothbrush technique won't polish the frets. If you're not too keen on using 0000 steel wool to do this (and I don't blame you), Planet Waves makes a product called the Fret Polishing System. Basically, it's super-fine polishing paper that's packaged with a protective stiff paper template that covers the wood while exposing the fretwire. The template fits medium or jumbo frets and you can use the kit on maple or dark fretboards.
Fig. 9. Planet Waves' Fret Polishing System includes super-fine abrasive paper and a guard to protect the wood.
Simply lay the template over the fretwire and polish the frets until they glisten (Fig. 9). The kit works great and there is little mess to clean up. But even with this system, you'll want to vacuum the residue off the neck left by the polishing paper.
Cleaning and Conditioning a Bridge.
Fig. 10. Like the fretboard, an acoustic guitar's bridge needs to be cleaned and conditioned.
It's very simple to clean and condition the bridge on an acoustic guitar. Remove the bridge saddle and then scrub the bridge with a toothbrush and conditioner (Fig. 10). Use cotton swabs to clean inside the saddle slot. When the gunk is cleaned off, wipe down the bridge with a paper towel. That's it!
Cleaning the Hardware.
Fig. 11. Filth can build up on a bridge and its saddles. When hardware gets this dirty and rusty, you'll need to disassemble and clean it with WD-40 or 3-in-One oil.
Sweat is a big enemy of hardware because its acids and salts corrode the metal plating and attract dirt that clogs up any moving parts. In extreme cases, a guitar's bridge (Fig. 11) and tuning keys (Fig. 12) can begin to rust. Cleaning these important mechanisms keeps them looking good and functioning at their best.
For cleaning metal hardware, I've had success with 3-in-One oil and WD-40. Remember that these products are only safe on metal, so avoid getting them on the fretboard or finish. I typically remove the hardware to clean it with an old toothbrush and then carefully wipe it off before reinstalling.
Cleaning the Finish.
When cleaning your guitar's finish, avoid furniture polishes like Pledge, which contains lemon oil, or products that contain d-Limonene, alcohol, solvents, or silicone. All of these will damage the finish over time. Sweat is another finish-eater because it causes lacquer to soften and break down.
Water actually works well to clean a guitar finish. Use a slightly damp micro-fiber cloth to wipe away dust and grime, and rinse the cloth frequently to remove any debris. As for a good polish, I only use pure carnauba wax, which is safe for most finishes.
Controlling Humidity
Once your guitar is clean, you'll want to protect the wood with some type of humidifier. For a guitar that's stored in its case, I recommend the Humidipak from Planet Waves. It's a simple, accurate, and effective way to maintain the ideal humidity for your guitar. If you keep your guitar out in a studio or living area, try running an ultrasonic or warm mist humidifier in that room. For most stringed instruments, the optimum humidity level is 45 percent.
[Updated 3/24/22]
Upgrading your tuning keys can help you get in tune more easily and stay there. Learn how to choose the correct keys for your guitar.
Machine heads, tuners, tuning keys, gears, or pegs: Whatever you call them, these devices determine how easily your guitar gets in tune and stays there. It’s worth investing in high-quality tuners, but do some homework before you upgrade.
A good set of tuning keys can make an enormous difference in how well your guitar performs. Many guitars come from the factory with inexpensive tuning keys, so it’s usually a good idea to upgrade them. But before you open your wallet, be sure you choose the correct keys for your guitar. Trying to install keys that don’t fit properly can devalue your instrument and cause mechanical problems. Fortunately, you’ll be able to avoid these issues with a little knowledge.
Some background. Guitarists and luthiers use various names for tuning keys, including machine heads, tuning gears, tuning pegs, and of course, tuners. In the early days of the guitar’s evolution, there was little choice when it came to replacing your keys. Only a few companies made “geared keys.” Before that, most lutes and guitars used friction pegs, like those found on a violin. These pegs were generally made from hardwoods and were very difficult to use.
Boasting art-deco knobs and cast housings, these sealed Grover Imperial tuners
are often found on archtop jazz guitars.
One of the first known manufacturers of a geared tuning key was John Frederick Hintz, who developed his device in 1766. It was revolutionary at the time, but became obsolete by the 1800s when John Preston developed a superior design. Most antique keys had a very low turning ratio and were poorly geared. The result was tuners that would slip out of tune, making life difficult for performers.
Fast forward to the present, where we have dozens of choices. Gotoh, Sperzel, Waverly, Grover, Planet Waves, Kluson, and Schaller are among the manufacturers of high-quality tuners, and these companies offer models that retrofit most guitars and provide superior gearing.
Decoding a tuner’s ratio. When describing their tuners, manufacturers include a ratio in the specs. This two-digit number tells you how many times you have to turn the tuning key’s button for the string post to make one full revolution. The lower the gear ratio, the fewer times you have to turn the button for the post to make a revolution. Conversely, the higher the ratio, the more times you have to turn the button for the post to revolve completely.
A relatively recent arrival to today’s tuner scene, Waverly keys have rekindled interest in the old-school, open-gear design. They may look like ancient, inexpensive keys—the kind once used on budget or student guitars—but they’re precision machines.
Using a flathead screwdriver to remove vintage-style mounting screws.
Because a higher gear ratio lets the post rotate in smaller increments, you have more control over the tuning process. In other words, an 18:1 ratio offers a finer degree of control than an 11:1 ratio. Lower ratio keys make it harder to reach a precise string tension, and this can cause you to jump past the desired note as you tune up.
Modern replacement keys have a much higher gear ratio than vintage keys. For example, modern Grovers have ratios from 14:1 to 18:1. New Klusons are as high as 19:1. Gotohs range from 14:1 to 28:1, and Graph Tech’s new Ratio sets have variable ratios, from 39:1 on the low E to 12:1 on the high E.
Look beyond the ratio. If you’re planning to upgrade your tuners, there’s more to consider than just the gear ratio.
For starters, if you have a vintage guitar (or an expensive modern instrument) and the keys are deteriorating or not working properly, I recommend installing direct replacement keys that do not require any modifications. Whenever you drill new holes or enlarge the existing holes in the headstock—or anywhere, for that matter—it devalues the instrument.
For a vintage axe, always store the original keys in a safe place to preserve them. Gotoh, Kluson, and Grover make excellent direct replacement keys that typically offer higher ratios than vintage tuners, but are otherwise a drop-in retrofit for Strats, Teles, Les Pauls, and other popular models. If you do the research and find the right tuner, you can make a clean installation with simple hand tools. We’ll cover this in a moment.
If you have a modern instrument and decide to install tuners that aren’t direct replacements, be aware that this usually affects the guitar’s tone. When you change mass on the headstock—by adding heavier or lighter hardware—it changes how the neck responds to string vibration. It’s hard to predict exactly how the tone will change—and guitarists debate this endlessly—but if you like how your guitar currently sounds, think twice before you install non-direct replacement tuners.
Locking keys. If your guitar has a vibrato arm or tremolo bridge, locking tuners can really help you keep in tune. Locking tuners clamp the string in place either by using a rod inside the post or a collar that wraps around the post. Both methods are effective and eliminate the need to wind the string around the post more than once. When you eliminate multiple windings, the string doesn’t have to reseat itself on the post when it returns to pitch after being slackened. Companies that make direct locking replacements for existing keys include Planet Waves, Schaller, Sperzel, and Gotoh.
Staggered-height posts. If you have a flat headstock with six tuners in a single row—like those on a Fender—think about upgrading to tuners that have staggered-height posts. On most guitars, staggered-height tuners eliminate the need for string trees, and this too can improve tuning stability—especially on guitars with whammy bars. Staggered tuners typically have posts in three sizes: strings 1 and 2 take the shortest posts, strings 3 and 4 take the medium ones, and strings 5 and 6 use the tallest.
If the staggered height tuners aren’t direct replacements for your existing tuners, remember that changing the mass on your headstock has sonic consequences. You might actually like this, but you can’t really predict the outcome in advance.
Changing your keys. If you select direct replacements for your existing keys, installing the new ones is a simple process. Typically, you need a small screwdriver (flathead or Phillips) and sometimes a 10 mm nut driver or a deep-well socket.
Most modern keys use Phillips-head screws.
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.