Why Did My Guitar Come With An Allen Wrench?

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You happily picked up a guitar at a guitar shop. As you happily unpack it, you notice that it comes with an Allen wrench or a hex key. You try to look around the guitar but cannot find a place to fit in the Allen wrench. At this point, you question why your guitar comes with an Allen wrench.

The Allen wrench on your guitar is meant to adjust your truss rod. The main function of it is to keep your guitar neck straight, as strings and other forces may pull it in another direction. You may use your Allen wrench to do so. The adjustment position is often on the headstock, right behind the guitar nut.

In this post, we discuss a truss rod and how to adjust it using an Allen wrench. We also discuss why guitar necks bend over time.

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Why Did My Guitar Come With An Allen Wrench?


What Is An Allen Wrench?

An Allen wrench is an L-shaped tool used to install and remove hexagonal fasteners. They are made of a single piece of material, usually metal, bent into an L-shaped angle. Allen keys have hexagonal ends on both ends. You may use both ends of the key to removing fasteners.

An Allen wrench is also known as a hex key or Allen key. It is an L-shaped tool used to install and remove hexagonal fasteners. They are made of a single piece of material, usually metal, bent into an L-shaped angle. There may also be Allen wrenches bent into different shapes. 

An Allen key has hexagonal ends on both ends. You may use both ends of the key to removing fasteners. The end with a longer handle may provide more leverage and torque, which may be useful to remove tighter fasteners. For example, the other provides a deeper reach, which may help if the fastener is deep inside a socket hole.

Allen keys work like your common screwdrivers, with a few exceptions. You can use them by inserting one of the ends into a hexagonal socket head fastener and rotating it. Moving the Allen key clockwise tightens the fastener while turning it counterclockwise loosens it. Continue to loosen the fastener to remove it.

Allen keys “grip” fasteners much better than other popular screwdrivers and wrenches because the friction surface is larger. This firm grip prevents fasteners from becoming stripped.

Allen keys are also frequently bundled with consumer-built products due to their low costs, such as furniture or guitars. Customers can assemble, adjust or tighten the parts using the accompanying Allen keys in the future.

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What Is A Truss Rod?

A truss rod refers to a metal rod that runs the length of the neck of a guitar from the nut to the heel. The truss rod’s most important function is to provide sturdy support or brace the neck against the string tension. It is usually located just beneath the fretboard. It is accessible by a small hole behind the nut on most guitars.

A truss rod refers to a thin metal shaft that runs the length of the neck of a guitar. It usually travels from the nut to the heel, where the neck meets the body. 

It is usually located just beneath the fretboard. It is accessible by a small hole behind the nut on most guitars. The adjustment fastener is generally covered by a little piece of wood or plastic with screws. 

For acoustic guitars, the truss rod may be accessed through the soundhole. For a classical nylon string guitar, there are usually no truss rods. 

The truss rod’s most important function is to provide sturdy support or brace the neck against the string tension. On a commonly well-tuned acoustic guitar with light gauge steel strings, the pressure may be as high as 180 pounds. 

If unchecked over time, the force may bend and eventually break the neck. The truss rod balances the tension so that the neck does not bow or break under pressure.

Over time, the wood may bend slightly due to age and tension. This is when a truss rod adjustment is needed to reshape the neck again, to make it straight. To adjust the truss rod, an Allen wrench is often used.

Some players wrongly assumed that the truss rod is used to set a guitar’s action, which isn’t strictly true. Action is used to describe the distance between the strings and the neck. 

Low action meant the distance was short, making pressing the strings easier. Turning the truss rod may help, but it would not be the best solution for lowering action.

Why Do Guitar Necks Bend Over Time?

Guitar necks may bend over time due to humidity, temperature changes, and pressure from the strings. Guitar necks may bend in two ways, bowing and twisting. You may correct the bowing problem by adjusting the truss rod. For twisting, however, you may need a luthier to help correct the issue. 

Guitar necks can bend due to various causes, including heat, humidity, and time. Necks are composed of natural wood and are susceptible to humidity and temperature fluctuations.

Another factor is the natural pressure exerted by the strings. A set of regular thin gauge guitar strings may pull up to 180 pounds of force on the neck. This may gradually warp the neck, causing it to get out of alignment. 

That is why, once you complete playing, you should tune your guitar down a half-step or a full step to relieve the strain from the strings on the neck.

Aside from these factors, the wood material, how it is cut, and the aging process might result in the neck warping, twist, cup, or bow over time. Poor quality, poorly cut, or aged wood is less stable and more prone to bending.

Guitar necks can bend in two ways, by bowing or twisting.

Bowed Neck: The most common form of neck bending. It is usually caused by the pressure from the strings, causing them to bend inward, forming a U-shaped curve. Most guitar and bass necks are typically slightly bow-shaped to make playing easier. This is commonly called neck “relief.” 

However, excessive bowing may result in playing difficulty. For example, the strings may get very close to the fret on the first few frets and further from the fret as you play closer to the soundhole.

Twisted Neck: Your guitar neck is considered to be twisted if it is rotated around its long axis. This may cause the fretboard to be uneven and hard to play. 

The problem may sound terrible at first sight, but in many cases, guitar necks twist a bit as they age, and they are commonly not visible to the eye. However, if the twisting is excessive, you may want to take it to a luthier for repair, as you cannot perform any adjustment yourself.

How To Tell If Your Guitar Is Bent?

You can tell if your guitar neck is bent by inspecting the guitar with your naked eyes, or you can use a luthier feeler gauge. The key is to check with your guitar maker to see the recommended bowing and to only adjust it if the bowing is excessive and not in spec.

There are many ways to tell if your guitar is bent or needs truss rod adjustment:

Frequent Buzzing: This may be the first tell-tale sign that your guitar is bowing too much. If the guitar is constantly or easily out of tune, or if the strings start to buzz when they contact the frets, you should consider further checking.

Naked Eye Inspection: You can perform a naked-eye inspection by looking down the bass and treble sides of the fingerboard separately with one eye closed. Observe any abnormalities in the guitar neck, whether straight, bowed, or twisted. Hold the guitar by the body rather than the headstock when performing this test. Reading from the headstock may not be as accurate.

Feeler Gauge Test: Get a luthier feeler gauge, and test the distance between strings from each fret from the board. Check the gap between the fret and the string of the high and low E strings on the 8th fret. This is because the curvature should be deepest there. 

Compare the readings with the recommended distance on your guitar’s user book of support. You may need to perform truss rod adjustments if they are not within the normal range.

How To Adjust Truss Rod Using Allen Wrench?

To adjust the truss rod, you start by determining the nature of the bending to decide if you need to tighten or loosen the truss rod. Once you have identified the location of the truss rod, you turn the rod with an Allen wrench, one quarter turn at a time. Once looking in spec, you may use a luthier feeler gauge to confirm the measurement. 

Adjusting the truss rod is a straightforward affair, although those doing it for the first time may want to be gentle with it. This is because extreme adjustment may break the guitar neck. 

To perform adjustment:

  1. Start by sighting down the neck of your guitar from the body. 
  2. Observe the bowing, whether the neck slopes down away from the strings or slopes up into the strings. 
  3. You may want to tighten the truss rod if the neck slopes down. You may want to loosen the truss rod if it is the other. 
  4. Identify the location of the truss rod. For electric guitar, it is often at the headstock, right behind the guitar nut. The truss rod should be in the soundhole, closer to the neck area for the acoustic guitar
  5. You often tighten the truss rod by turning your Allen key clockwise and anti-clockwise to loosen. 
  6. Tighten or loosen the truss rod a quarter turn at a time, and once completed, repeat step 1 to see if you need to further adjust the truss rod. 
  7. The key is to turn and adjust slowly and frequently check to ensure proper adjustment. 
  8. Once completed, consider using a luthier’s feeler gauge to check the distance between the string and the fret to ensure the action is in spec.

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