A guitarist may require replacement or additional parts because of damage to the original parts or because they want to improve the tone or appearance of the instrument. Although there's a thriving aftermarket in replacement parts for many guitars, there's very little on an acoustic guitar that is designed with replacement in mind, as opposed to electric guitars, where electronics can be upgraded and replaced, and where on some models, even necks and bodies can be swapped over. There are, however, a few components on an acoustic guitar that can be replaced, maintained, and upgraded, and we'll work our way through these in order from the headstock to the lower bout.
Machine heads, or tuning pegs/pins, come in two distinct styles for nylon-strung and steel-strung guitars.
Those intended for a nylon-strung, classical, or flamenco guitar are built in two sets of three, each on a single metal plate mounted on the side of the headstock, with plastic or celluloid rollers running across two apertures in the body of the headstock. Ideally, a replacement set should be sourced from the original guitar maker in order that the spacing between the tuning rollers, their diameter, and the mounting holes all match the machines being removed. Whilst the spacing is supposed to be standardised, as is the roller diameter, there could always be variations between different brands, leading to problems with the rollers being too big or too small for the mounting holes, possibly requiring larger holes to be drilled in the headstock. If an aftermarket set is purchased, see if you can get them on a trial basis from your supplier. Double-check all sizes of the new set against the old before fitting, and if it looks like there will be a mismatch, go back to the supplier and select another set by another maker.
Machine heads for steel-strung acoustic guitars are mounted to the back of the headstock, secured with screws, and have a metal tuning pin running through it from back to front, with a bushing or housing around the pin, inserted from the front. Again, if replacements can be sourced from the guitar maker, or from the maker's preferred brand, if the maker doesn't make their own, then these should be a direct retrofit, re-using the same mounting and screw holes, leading to a neat installation. The brand, and sometimes the individual model, can usually be found stamped or moulded into the body of the head mechanism. If the same brand and model of heads aren't available, there may be heads available from other makers designed particularly for that model of guitar. Again, the sizes of the pin holes should be standardised, but for some older or vintage guitars, some customisation may be required, and any new set of heads should be compared with the old once removed from the guitar to confirm all sizes.
If the neck of the guitar is fitted with a truss rod, the adjustment nut will either be found under the neck joint and accessed through the soundhole, or above the nut on the headstock. If on the headstock, it may be concealed under a plastic or metal cover. When buying a replacement truss rod cover, ensure it is either the same size or larger than the original fitment, otherwise replacement is likely to leave the mounting holes exposed.
Nut, Frets, and Fingerboard
Whilst replacement nuts and fret wire are available from many suppliers, replacement of these items is generally considered to be the domain of the professional repairer or technician. The skills and techniques involved in replacing a nut, fret wire, or even the whole fingerboard are acquired professionally over a number of years, and often require a number of specialised tools. Whilst the guitar owner could purchase these items and supply them to the repairer, it's probably best to meet the repairer face to face, discuss the work required, and take his or her advice on what replacements should be used and from where they should be sourced.
On nylon-strung guitars, and on most steel-strung models, the bridge is glued in place on the top of the guitar, and is non-replaceable and non-adjustable. The strings rest on an insert in the bridge, called the saddle, and in many cases, the saddle can be replaced, perhaps with an identical one if the original has become worn or damaged, upgraded with one of a different material, or is of a different type. On certain models, the saddle is unsecured, and with the strings removed, can be lifted out and a replacement dropped in.
The density and porosity of the saddle material both have an effect on the sound of the guitar, and the owner might want to experiment with different materials for the saddle. Although plastic and various types of advanced polymer are the dominant material for many makers and repairers due to cost considerations, many guitar makers in the past have used more exotic materials, such as bone and elephant ivory. The use of elephant ivory is illegal in many territories these days, and as a result, bone is the favoured material for many of the higher-end guitar makers. Some saddles are designed with intonation compensation, where the upper edge, where it meets the strings, designed to offer different string lengths for the B string, the G, or both.
The strings are secured to the bridge behind the saddle. On nylon-strung guitars, these are merely knotted through holes in the bridge, but on a steel-strung guitar the ball-ends of the strings are secured in holes with bridge pins. Replacement of the bridge pins can change the sound of the guitar, and possibly improve its appearance. Again, plastic is the dominant material for mainstream instruments, but be aware that even the plastic can vary between manufacturers, and a harder or softer grade will influence the sound. Other favoured materials include boxwood, a tightly-grained wood which has for centuries been favoured for fine detail work on hand-built furniture, and also ebony and rosewood. Ebony tends to produce a bright tone, while rosewood has a warmer tone.
Steel-strung acoustics are often fitted with strap buttons, or end-pins. One of these is attached to the lower bout of the guitar body, and another by the neck joint, although some guitarists favour attaching the strap around the headstock. Strap buttons are unlikely to need replacement, and rarely wear out, but some types of locking strap button are available. For the more active player, the lockable style might be the preferred choice. Replacement is merely a case of unscrewing the old, and inserting the new. Some makers of the bridge pins mentioned above will supply an end-pin with a set of bridge pins, to ensure a cosmetic match.
Many acoustic guitars are fitted with pickguards, or scratchplates, glued to the front of the guitar below the soundhole. In the normal course of events, these normally don't require replacement, but aftermarket items in various finishes are available, and could be a useful addition to a guitar which currently has none fitted.
There are a number of aftermarket parts or accessories which could be added to an acoustic guitar to enhance its performance, as opposed to replacing existing parts of the guitar. These could include magnetic or contact pickups, for the purpose of amplifying the instrument, additional or replacement pickguards, or even strings and carrying cases. Magnetic pickups are usable only on steel-strung guitars, and are usually found in designs which clip into the sound hole of the instrument. Contact pickups are usually secured to the top or bridge with adhesive or double-sided tape, and are suitable for both nylon and steel-strung guitars.
Finding Parts to Fit an Acoustic Guitar on eBay
From the eBay homepage, select Buy and Browse Categories. Select Musical Instruments, and Guitars. Parts can either be found under the Accessories subcategory, and Parts, selecting the Acoustic Guitar option, or via Acoustic Guitar within Accessories.
Replacement parts for an acoustic guitar can be used for the repair of damaged items, but can also be used to upgrade or enhance the instrument, either in terms of its tonal performance or visual appearance.