We all know what a guitar machine head is whether we think we do or not. They’re those things you twist when you tune your guitar.
Yes, they have many names – tuners, tuning heads, tuning pegs, gear heads, the list goes on. For the purpose of this article, we’ll call them machine heads.
There are actually six types (trust the guitar to over complicate it!)
In this article, we’re going to geek out and learn about each one. If you ever wanted to know the difference between an open back and a locking tuner, this is for you.
What is a Machine Head?
The machine head is a geared apparatus on the headstock of stringed instruments that tunes and adjusts string tension, and you’ll find them on most if not all stringed instruments.
While we may think its main purpose is to help change the pitch of each string, the gears’ main function is actually to impede movement (stop the strings slipping).
A tuner that lets a string slip is no good at all!
Back in the day, as documented by Alhambra Guitarras’ superb guide on the parts of the guitar, machine heads were commonly made from wood.
Things have moved on a bit, as we’ll see.
There are six main types of machine heads. We’ll explain the benefits and downsides of each as we go.
Vintage Open-Back Machine Heads
You can identify vintage open-back tuners from the exposed gear cogs on the back. They have press-fit brushing that fits in tiny ¼-inch holes drilled into the headstock.
Vintage open-back machines heads are the first choice for many people who play vintage guitars. They were standard on instruments from the 60s through the 80s, so they’re also a collector’s item today. Their charm and design fit vintage guitars well.
This option also tends to weigh less than sealed machines because they don’t have the protective housing. The less weight directly affects balance and the overall mass of the neck and headstock of the guitar.
The main issue with vintage open-backs is that they’re exposed to the elements.
Because the internal mechanisms and gears are exposed, they take on more damage from dirt and debris. You’ll notice they start to feel and look worn after only a few years.
Vintage open-back machine heads and usually rather ornate, and offer a detailed design that’s not cheap. Depending on your guitar and the frequency you play, you’ll have to pony up more money to fit a set of these.
A popular maker of this type is Waverly, shown in the image above – here’s the link to amazon.com (affiliate link) if you want a closer look.
Vintage Closed-Back Machine Heads
Vintage closed-back machine heads are functionally similar to vintage open-backs, but they differ in that they have casing (or housing) that surrounds the gears for protection.
They’re also fitted to the side, rather than the back.
The main advantage is longevity. The protective housing avoids dirt and debris getting in the machinery, the machine heads, as a result, stay in better condition.
One downside is the weight. The protective housing adds a bit of extra weight and with the placements of the machine heads on the headstock, the weight distribution of your instrument is affected.
Side-Mounted Machine Heads
Side-mounted machine heads are similar to vintage open-backs in design and aesthetics, but they differ when it comes to functionality. In fact, the two options are so similar that most people call side-mounted tuners by the wrong name.
The difference between the two is that side-mounted machines are attached along the side of the headstock. The gears attach differently. They also only come on classical acoustic or flamenco guitars with nylon strings. Therefore, you can’t use this option with an electric guitar.
A side-mounted machine head is typically metal with plastic handles. They come in sizes 4 cm, 5 cm, and 11 cm.
Like vintage open-back machine heads, side-mounted options are attractive in terms of their vintage aesthetic. The open gear design is ideal among many people with classical guitars.
Side-mounted options are also made for nylon strings, giving them an added advantage because it doesn’t take as much to keep the string in tune.
The biggest downside to side-mounted tuners, like vintage open-backs, is that the open design leaves them vulnerable to dirt and debris. Exposed gears are prone to wear and tear much faster than other options.
Sealed Tuning Machine Heads
You can identify a sealed tuning machine head because you won’t be able to see the gears. The housing contains the gears, keeping them protected from dirt and debris outside.
Sealed tuning machine heads come in two options:
- Sealed tuning nut with indexing pin: An indexing pin sits under the housing to hold the machine in place. Without the need for a screw, the string holds the machine in place using tension.
- Sealed tuning nut with mounted screw: The most common type, sealed tuning nuts come with a screw that holds the machine onto the guitar’s headstock.
Depending on the brand, the holes can range from ⅜-inch to 10 mm.
A ‘diecast’ housing encloses the cog gear and the worm so that basically all the gears are surrounded with a metal alloy. This keeps dirt and debris out, allowing your tuners to last much longer and keep them permanently lubricated.
They should stay lubricated for life. They won’t wear out as quickly as other types of tuners due to abrasive contamination or anything else interfering with the working parts of the machine, which can wear down the teeth of the gears over time and make it more difficult for the machine to stay tuned.
Locking Tuning Machine Heads
Locking tuning machine heads offer a locking screw built onto a sealed housing.
They increase stability in your tuning by adding pressure to the strings, holding them in place. They also add complexity, which can cause a lack of flexibility.
The clamping mechanism of this type of machine head locks the string in place. This means you can use fewer string windings for stable tuning. They should help your strings stay in tune longer.
The one downside is they’re a bit fiddly and the restring process is more complicated than the usual wrapping a wire around the tuning post (like you normally do).
Guitars like the Floyd Rose locks the strings at the base of the headstock (or where it meets the fretboard).
Staggered Machine Heads
Staggered tuners are often found on guitars that don’t have an angled headstock or use string retainers.
With this type, the tuning posts change in height from low E to high E. The high E string tend to have the shortest height, with the tallest height at the low E string.
This helps create the best angle for the string to rest on the nut (or along the top end of the fretboard).
The area between the machine head post and the nut is called the break angle, which is important because the angle alters the amount of pressure pushing down on the nut.
Without the proper pressure, the quality and sustainability of the sound aren’t as great. It can also cause what’s called ‘fret buzz’, which happens when the string slips out of tune.
The posts coming in varying sizes also can cause issues with fitting. If you don’t install the machine heads just right, you’ll instantly head a negative effect on intonation as you play.
There are probably other types we haven’t mentioned, but these were the main ones we came across when we researched the topic.
We hope you enjoyed the article and learned a bit.
Thanks for reading 🙂