My acoustic-playing friend Colin was asking me recently for some advice about a buzzing he was getting from the strings on his guitar. That inspired me to write this installment in the series of tutorials about guitar hardware.
There are two main components which we're going to look at here, namely the guitar neck (the long piece of wood which runs from the guitar body to the headstock) and the fingerboard (the slab of timber which sits on top of the neck, into which the frets are set).
Guitar necks are nearly always made from timber, although in the past manufacturers have experimented with alternative materials such as carbon fibre and even aluminium.
A key factor in choosing a guitar is how the neck feels. Necks come in a wide range of 'profiles', ranging from shallow 'C'-shaped through to fat 'D'-shaped. Some necks also come with a more 'V'-shaped profile. Choosing a neck is largely a matter of personal taste, and is often influenced by the style of music that you play. For example, some metal guitarists prefer a slimmer neck profile as they find this profile better suited to fast moves up and down the neck. There is, however, a trade-off to be made; the amount of material influences the sound, as a fatter neck has more material to carry sound than a slim one.
The finishing on the back of the neck is an factor that should be taken into consideration when buying a guitar. A heavily laquered neck may look nice and shiny but may not be as comfortable or 'fast' as one which has been given a satin or oiled finish.
Something which is often taken for granted is the sheer stress that a guitar neck is placed under. The tension in a regular set of strings is somewhere in the region of 45-50Kg (around 100 pounds) which is an incredible amount of force for the neck to stand up to. For this reason, a steel rod called a truss rod is fitted inside the neck. As well as simply strengthening the neck, the truss rod can be adjusted to compensate for specific string tensions.
When the truss rod is too slack, the neck bends to form a bow - the tension in the strings is greater than that of the truss rod and so the headstock is pulled towards the body. This raises the strings higher from the fingerboard and makes playing more difficult. When the truss rod is too tight, a crown forms in the neck - the tension from the truss rod is greater than the tension in the strings and so the headstock is pulled away from the body. In this case, the middle part of the neck is higher and this causes the strings to buzz against the frets.
The method of truss rod adjustment varies from guitar to guitar. There will either be a slot in the headstock next to the nut (sometimes hidden with a plastic cover) or at the base of the neck where it joins the body. Unless you know what you're doing, leave truss rod adjustment to a professional guitar repairer - it is possible to cause severe damage to your guitar by setting the truss rod incorrectly.
The fingerboard is generally a separate piece of timber glued to the top of the neck. The truss rod is fitted into a groove in the neck before the fingerboard is fitten. There are some guitars with one-piece neck/fingerboard construction - these have the truss rod fitted through the back of the neck, resulting in a 'skunk-stripe' fillet of wood in the neck.
Whilst not as significant as factors like neck profile, some characteristics of the fingerboard have a bearing on how a guitar feels to play; the material, the profile and the width.
As with the rest of a guitar, the timber used for the fingerboard influences the overall sound. The most common woods used for fingerboards are rosewood (a fairly dark-coloured wood which has a a slightly fatter sound than maple (a light-coloured wood, also often used for necks) which imparts a relatively bright sound. You may also encounter guitars with an ebony fingerboard (another dark wood) but due to its releatively high cost this tends to be found on higher specification (and cost) instruments.
The profile of the fingerboard refers to the degree of curvature. Unlike a classical guitar which has a flat the fingerbord, a steel string guitar's fingerboard has a slight curve to it. The easiest way to think of this is to imagine a cross-section out of a cylinder. Flatter fingerboards are better suited to modern techniquest such as tapping.
When a string is bent, it has the tendency to 'choke' against the frets. To remedy this, some guitars have what is known as a compound radius fingerboard. Whereas a regular fingerboard is like a cross-section of a cylinder, a compound radius fingerboard is like a cross-section out of a cone. The fingerboard gets progressively flatter as you move up towards the higher frets.
The frets are fitted into slots in the fingerboard, and should be a tight fit with no sharp edges protruding. As the fingerboard is made of timber, it can be affected by atmospheric conditions. Even a well-seasoned piece of timber is liable to contract slightly and it may be necessary during the life of a guitar to have to get the edges of the frets filed off.
The fret wire itself comes in a range of profiles (low/wide, tall/thin) and these can affect the way the neck feels, although this is largely a matter of personal style and preference. Frets will wear down over time and will require occaisional 'dressing' (filing to obtain a smooth, regular profile) and even eventual replacement. Such tasks require specialist tools and experience and so you should not attempt these as a casual DIY task - leave it to the professionals.
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