What Is The Nut On An Acoustic Guitar?

The nut is a small piece of hard material located towards the headstock end of the neck. The basic functions served by the nut are: 

1. It supports the strings as they cross from the headstock to the neck.
2. It forms an anchor point on one end of the vibrating length of each open string, thereby aiding in the transmission of their vibrations to the neck.
3. It consists of equidistant grooves to hold all the strings in position. The spacing of grooves in the nut sets the string spacing over the length of the neck.
4. Nut, in conjunction with the bridge saddle (anchor point at the other end), regulates the height of the strings above the fingerboard.
5. Distance between the nut and bridge also defines the vibrating lengths of the open strings, called scale lengths. 

What Is The Best Material For A Guitar Nut?

The nuts made from materials such as ivory, bone, ebony, metal, graphite, ceramics, epoxy resin products, some hardwoods, and even plastics are available. One of the above materials can be selected based on your budget, playability, and tone requirements. Well-constructed nuts made with quality material can significantly enhance the effectiveness of your guitar.

To fulfill the above functional requirements, nuts should be made from hard and dense materials. Denser materials have the ability to transmit sound more effectively, whereas hard materials are more wear-resistant. We will now discuss the suitability and effectiveness of the above materials for making a nut. 

In olden times even dark hardwoods were used. These provided a decent look but resulted in a softer open string tone. 

1. Ivory: Traditionally, in high-end instruments, the nut and saddle were manufactured with elephant ivory. Now embargo has been imposed on this to save the elephants from extinction. Fossilized ivory consisting of Walrus and Mammoth ivory is now used to make nuts and saddles. This is from tusks of animals that died a hundred to thousand years ago. This material is hard and has good acoustic properties and aesthetics. Hence it provides bright sound, resonance, and sustain. It is however difficult to work with.
2. Bone: Arguably, bone is considered the best material in contemporary times for nut construction because it fulfills the requirement of high density and hardness. In addition, it is light, durable, and can withstand extensive mechanical shocks. Proper slotting and installation ensure desired degree of resonance, attack, and sustain. Due to this, it is used on many high-end instruments. The bone is usually derived from the beef thigh. The bone must be looked for inconsistencies like a softer spot before working.  Some manufacturers bleach the bone to make it look whiter, at the cost of softening it. This affects the very characteristics for which the material is preferred in the first place in addition to impacting tone and life expectancy.
3. Metal: Brass and steel nuts are commonly used where durability and appearance is an important considerations. Metal nuts have large life spans with minimal maintenance. They look very nice when properly polished. The sound performance is reasonable. However, a lot of effort is required in cutting and slotting them
4. Plastic: Budget instruments are frequently fitted with molded plastics. They neither sound well nor are able to hold up as well. Hollow molded pieces are even worse as they are not suitable for transmitting sound and eventually collapse also under the string tension.
5. Ceramics / Epoxy resin-based: Next up the ladder are synthetic materials made from ceramics and epoxy resin, which are harder and composite with better sound quality and serviceability. Common materials in this category are offered under brand names such as Corian, Micarta, and Tusq.  Corian is widely used by Gibson. 
6. Graphite, PTFE, and lubricating nuts:  Some synthetic materials are impregnated with lubricating materials like graphite, Teflon, or PTFE to form different types of lubricating nuts. They offer tuning stability and a variety of tremolo effects. 
7. Ebony: It provides a good appearance and sound but softens quickly compared to other materials.

How High Should The Nut Be On An Acoustic Guitar?

Ideal String height above the fretboard, also known as action is 0.007″ to 0.009″, when measured between the string and the first fret, with the string pressed down at the fourth fret. In fact, this distance is so small, that it can be barely seen, but has a big impact on the overall playability and how your guitar sounds.

Normally, the first string of the guitar has a diameter in the range of 0.010″ to 0.013″ for extra light to medium gauge strings. If the first string of a known gauge is able to pass under any string, the string has high action. You can then measure actual string height with the help of a feeler gauge.

Telling low string height is much easier. Press each string at the fourth fret and pluck it between the nut and the fourth fret. If you get some tone in the sound, the nut is not too low. If all you get is a heavy buzz or dead thuds on plucking, you need to raise the height.

Advantages & Disadvantages Of High-Action

Higher action eliminates the buzz and results in more sustain on the notes. This is due to the absence of any obstruction in the path of the vibrating string.

However, it is difficult, painful, and tiring to press strings with high action on the strings. With tired hands, you may get what is known as beginner buzzing, which is a direct result of an inability to press the strings on the frets of your guitar firmly. The problem is further compounded if you are a beginner and use a thicker set of strings.

High action also leads to intonation issues, which means that the guitar will sound out of tune in some areas of the fretboard, particularly at the lower frets. Even the open chords may not sound right in such cases.

Advantages & Disadvantages Of Low-Action

As against the high-action, strings with low-action are easier to press and kind on your fretting hand, more so if you are a beginner, till you have developed adequate finger strength.

But, lower action leads to buzzing noise with every note or chord you play. This is caused by contact with the vibrating strings with different frets. There may be no sound produced at all in the extreme case, something called fretting out. Lower action may also reduce the sustain due to interaction with other frets.

Once you have acquired a fair level of expertise in playing, it is desirable to have your guitar nuts and frets adjusted by a pro.