If you are thinking about changing your guitar machine heads it's important to consider a few key points before diving in with a string winder and screwdriver.
Of course, if you are simply replacing the original ones with an identical set then you should find the process to be a very straightforward change-over.
Switching to a different style of machine heads can become slightly more problematic. For instance, you might want to replace the old, clunky 'vintage-style' set that came fitted from the factory with a modern locking machine heads for improved stability and easier string changes. In this case, the mounting screw hole locations might differ, which could mean you'll need to fill the existing screw holes on the back of the headstock and re-drill for the new set.
However, this isn't the only potential problem that you might encounter - while often overlooked, the tuning machine bushings can also vary in design and size causing more unexpected problems if interchanging between two different tuner styles. In this comprehensive guide, we'll explore the evolution of these important guitar parts, from the bushes that are associated with vintage-inspired machineheads to the ones that come with more modern diecast tuners. Whether you're a seasoned luthier or a curious guitarist, this article will equip you with the knowledge to make informed decisions about your electric guitar's tuning machines and bushings.
The Importance of Tuning Machine Bushings:
Tuning machine bushings, also known as tuner bushings, provide a stable fitting for your electric guitar's tuning machines (or machine heads) within the headstock. They provide stability, prevent wear on the wood, and contribute to the overall look of your instrument. The right bushings can enhance tuning stability and make string changes easier, while poorly fitted ones can lead to tuning issues and even damage to your guitar's headstock.
Understanding Machine Head Bushings
First, it's important to recognise that machine head bushings come in different styles to accommodate different types of tuners. The two primary categories are vintage push-fit bushings and modern screw-in bushings.Vintage "Push-Fit"
A modern recreation of a vintage design: the Gotoh machine head comes with the push-fit bushing, just like the originals found on instruments from the 1950's and 1960's. You can see the ridges around the edge of the bushing to help it bite into the wood of the headstock.
The Vintage Era: Kluson Push-Fit Bushings
Let's start our journey with the classic Kluson push-fit bushings. These were widely used in many vintage electric guitars, particularly those from the 1950s and 1960s. These push-fit bushings are designed to press fit snugly into a 3/8" (9.5mm) hole in the headstock. Their simplicity made them a favorite among manufacturers and were a staple of the traditional Kluson design.
Push-fit bushings are typically made of nickel-plated brass and have a slightly flared shape. This design allows them to be pressed into the headstock hole, where they're held in place by friction. The flared end sits flush with the surface of the headstock, providing a clean, vintage look. Most vintage-style machine head sets come complete with these push-fit bushings, such as the Gotoh SD91 or SD90 sets.
Installation Tips for Push-Fit Bushings (Fender-style headstocks):
It is crucial to check that the headstock holes are the correct size for the push-fit bushings included with the replacement set of machine heads
Ensure the headstock holes are clean and free from debris. Measure the hole diameter carefully - they should be exactly 3/8" (9.5mm) for a proper fit. The most important thing to remember here is the fit should be snug but never too tight - crucially you never want to force them into the hole because this can result in a damaged headstock. Conversely, being able to push the bushing in with just your thumb is probably a little too loose. There are specialised bushing press tools specifically made for this job, but they can be quite expensive. These tools are worth it if you plan to fit bushings to several instruments but may not be cost-effective if you're only modifying your main guitar.
The cheaper and more traditional method is to use a hammer. Once again, you'll need to exercise restraint and caution when doing it this way to avoid damage. Using a piece of wood on top of the bushing will ensure the hammer head doesn't mark the top of the bush. Rest the guitar on a flat surface and gently tap the bushing in (tap not hit!), taking care that the bushing is not going into the headstock hole at an angle.
It's also possible to use a G clamp to slowly push it into place as you tighten but a further piece of wood will be needed to place behind the headstock.
Angled headstocks:
Gibson guitars with angled headstocks, whether the traditional 17 degrees or the 14 degrees used in the late 1960s, require extra care. These headstocks are prone to breaking if too much pressure is applied while fitting the bushings. Please proceed with caution!
If you are not feeling confident enough or don't have the necessary tools then we always recommend taking your guitar to your local qualified guitar Luthier who can carry this work out for you.
The Eyelet Style: Stamped Brass Press-Fit Bushings
Going even further back in time, we encounter the eyelet style bushings. These simple stamped brass press-fit bushings were a staple in many electric guitars from the early 1920s through to the 1960s. Like their successors, they're designed to be pressed into place, with the flared end sitting proud of the headstock surface. These ones didn't have the small ridges around the outside to help bite in the wood of the headstock hole. There are not nearly as common but this design provides a distinctive vintage look that many guitar enthusiasts appreciate.
Contemporary Screw-In Bushes
We can see this contemporary Gotoh machine head is supplied with the threaded hexagonal bolt that screws directly into the tuner.
Modern Times: Diecast Tuners with Screw-In Hex Ferrules
Fast forward to today, and we see many modern electric guitars equipped with diecast tuners featuring screw-in hex ferrules. Actually, we refer to this design as 'contemporary' and yet this design of bushing (or ferrule) actually started to show up in the 1970's when Grover tuners became the favoured upgrade with guitarists. With Grover's sealed housing and improved ferrule design, they offered a better level of tuning stability over the original Kluson's from the '50s and 60's.
The screw-in bush such as the Grover diecast Rotomatic machineheads typically require a larger 10mm hole in the headstock and work in a different way where the bush is threaded on the outside and screws directly into the guitar tuner, removing the need for bushes to be held into the headstock. The advantage of this design is increased stability and a more secure fit, which can contribute to better tuning stability.
These modern bushings often come as part of a complete tuning machine set. The hex shape of the ferrule prevents the bushing from rotating in the hole, while the threaded design allows for a secure connection to the tuner body.
Installation Tips for Modern Screw-In Bushings:
While holding the tuner in place from the back of the headstock, screw on the bushing and nut from the front, keeping them just barely finger-tight. Align the tuner at the back and secure it with the small mounting screw that came with the tuner. Then, tighten the bushing from the front using a spanner, wrench, or one of our handy Hosco Nut Cubes. Avoid using pliers, as they can damage the plating on the nuts and if you slip, also scratch the front of the headstock. Also, be careful not to over-tighten, as this can damage the bushing.
Bridging the Gap: Push-Fit Adapter Bushings
This 1967 ES-335 has had a replacement diecast set of machine heads fitted to it at some point in it's life. This means it will have had the headstock holes reamed out to 10mm. To return this back to a more period-correct set of machine heads then some push-fit adapter bushings will be required.
What if you want to fit vintage-style tuners to a headstock that's been drilled out for contemporary tuners? Enter push-fit adapter bushings. These clever little components allow you to effectively "downsize" your headstock holes, making it possible to install vintage-style tuners in a modern electric guitar.
Adapter bushings typically consist of a larger outer sleeve that fits the existing 10mm hole, and an inner hole sized for vintage 8.85mm (11/32") tuner posts. This allows you to maintain a vintage look while taking advantage of modern tuning stability.
Just to add a little bit extra complication to proceedings, that there are two sizes of conversion bushings: 10mm and 10.5mm. The 10.5mm size is necessary for more modern Fenders. Regardless of your guitar type, it's always a good idea to remove a single tuner and check the hole diameter before ordering your bushings.
Installation Tips for Adapter Bushings:
The same applies here as it does with the smaller-sized push-fit bushes above. Ensure the adapter bushings are fully seated in the larger hole before installing your vintage-style tuners. The fit should be snug but never too tight - if you feel like the bush won't even start to go into the hole then chances are the hole in the headstock is not wide enough - forcing it can result in damaged headstocks. We always recommend taking your guitar to your local qualified guitar Luthier who can carry this work out for you.
Final Thoughts
Understanding the different types of tuning machine bushings and their corresponding headstock hole sizes is crucial for anyone looking to maintain, restore, or modify their electric guitar. Whether you're working with a vintage instrument or a modern axe, choosing the right bushings can make a significant difference in both the look and performance of your guitar.
Remember, while replacing guitar hardware is a task that many of us can handle with some basic knowledge and tools, there's no shame in seeking professional help for more complex modifications. The right bushings, properly installed, can enhance your guitar's tuning stability, ease of use, and overall aesthetic appeal.
Whether you're restoring a classic electric guitar to its former glory or upgrading a modern instrument with vintage-style hardware, paying attention to the details like tuning machine bushings can make all the difference. For a selection of high-quality bushings and tuners, check out our Tuning Machines section.
Happy modding and may your strings always stay in tune!