Home     Mandolin Nut Fitting    Hospital    Setting Up

   When fitting a new nut to any floating bridge instrument, often done in conjunction with fitting a new bridge, there are some fixed and some preferential elements. The style and material are matters of individual choice, but remember different nut materials will give different effects, if only on the open strings. The thickness, height and string spacing of the nut are determined much more by the attributes of the instrument, though there is some latitude in how high the action will be. If the nut is badly fitted, never mind how good the instrument is, it will affect the sound. Below is an outline of the technique I use to fit nuts to both new and old instruments. I have found, often to my cost, that when you want to know how something is done, the 'expert' sometimes inadvertently assumes some knowledge...... very frustrating if you don't have it. So, for the purposes of this page, like the bridge page, I have assumed no prior knowledge whatever! If you have some, just skip those bits. I have also tried to outline a method that can be tackled by the least 'DIY-minded'. I hope I have succeeded.

     Tools: As with bridge fitting, you will need the same few basic bits to accomplish this.... file, sandpaper (80, 400), masking tape, long straight edge, small steel rule (showing mm.), craft knife, pencil, needle files (from most craft shops), a vice is useful.
    What are we trying to achieve? When we have finished, we aim to have a nut, where.... 
  • 1) the string pairs sit evenly spaced on the nut; 
  • 2) the foot of the nut itself makes good clean contact with the head/neck/fingerboard;
  • 3) the nut needs to 'stop' the string cleanly (in the case of no 0 fret);
  • and 4) the height of the strings above the 1st fret, gives us a low, easy, playing action. 
    How do I know what strings to use? See the tuning page for options for different members of the 'floating bridge' family.
1     Nut Types: on mandolins I have found 3 basic kinds of nut.

1. Simple nut; a bone block, sitting directly on the neck at the end of the fingerboard, stopping the strings. May also be made of ebony, rosewood, or mahogany, but also plastic and solid brass ones.

2. Nut and 0 fret; a bone block that holds the strings in place, but the zero fret 'stops' them. There may be a small gap between them. Again this type of nut may occasionally be wooden. Its job is primarily to keep the strings correctly spaced on the 0 fret.

3. Shallow nut; either of the above, but the shallow nut is mounted ON the fingerboard itself. A slot is cut from the end of the fingerboard, on which the shallow nut sits.

Other Variations:

4. Brass nut and 0 fret, in this case in 2 separate pieces on a Rinaldi.

5. Brass nut and combined 0 fret on Maglioni.

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Nut Fitting

  If you are adjusting a nut after fitting a new bridge, go to step 6: fine tuning

   Step 1: You must first choose a hard material for the nut and cut it to size. Bone is most often used, though there are many modern resins that are as dense. You will sometimes find nuts of ebony or rosewood on old instruments. 

   If you are replacing a nut, cut it the same size as the old one, but a little taller. For a nut where the original is missing, cut it as wide as the fingerboard at the head end, tall enough so it is proud of the fingerboard by about 2-3mm, and about 3-5mm deep, depending on the angle of the headstock. Here a bone nut is in the process of being cut to the size of the original.
   Step 2: Fit the nut foot carefully to the nut slot. Finish the nut off to about 1mm above the fret height. I generally round off the sharp edges of the top of the nut, but NOT the edge or corners that will receive the strings. Theoretically, the string height on the nut should be exactly the same height as if they were sitting on a 0 fret. I generally leave them a shade taller, to allow for fine tuning.
   Step 3: Next the string positions must be marked out. See the table below for typical spreads on the nut. String pairs need to be close enough to be able to be played together easily, but not close enough to touch when vibrating, generally not closer than 2mm. They need to be as close to the sides as is possible without fingers slipping off the edge, often as little as 1mm on the light-weight Italian instruments. 

   Bear in mind when spacing the pairs, that 3rd and 4th are wider, so will need a little larger space, and thus distance between them. Also, the centre pairs are often angled outwards, to take the strings 'out' towards the tuners.
   Step 4: The next step is to start the string slots. Holding the nut in a vice, use the narrowest, finest saw blade that you have; cut at an angle, parallel with the face of the head, being careful not to go far into the front face. Slots can be widened and deepened with a file or old string to fit later.

   If you have a 0 fret, then the slots will need to be cut below the level of the frets, and angled down at the same angle as the head. If there is no 0 fret, they will need to be cut no deeper than just above fret height, no more than 1/2 mm, and again angled down like the head.

   Always under-saw, as you can go a little deeper if necessary......  if you go too far, you cannot undo the cut.

  
   Step 5: The slots need to be fitted to the individual string sizes. I tend to use a saw and a needle file to start, and a piece of old or off-cut string (3rd and 4th) as a file to finish off. The slot needs to be wide enough to fit the string with no room for vibrations within the slot. The front edge of the slot should 'stop' the string cleanly, hence the slots angled down towards the head.

   I tend to use an old E string and an old G string to try the setup on 1st and 4th. Now is a good time to glue in the nut. You must then fit your strings and gradually tune up. Once in tune you can examine your efforts.
   Step 6: Fine tuning. You will probably need to make small adjustments once the strings are fully tuned. I try to avoid taking strings off to do this, slackening off enough to pull back a string and file/saw a slot, then tuning up again to test it. Rattles or buzzes at this stage are difficult to find, especially if you have also renewed or re-fitted the bridge. I have found a hand lens very useful for spotting those strings you thought were resting on the 0 fret. 

   In an easy action, you should only be able to slip a thick piece of paper under the string at fret one, but not a piece of thin card. At fret 12, the string should be between 1.5mm and 2mm above the fret. Higher makes the action slow and harder to play, lower can result in rattles and buzzes as the instrument moves in reaction to changes in temperature and humidity.

 I have found Stew Mac's graduated saw set extremely useful in cutting bridge and nut slots. 

Gauges are 0.008" 0.010" 0.015" 0.020" 0.025" at around 40$

 

   Typical String Setups on the Nut:
  Nut Width Edge 4th width space 3rd width space 2nd width space 1st width Edge
Mandolin: 30mm   3mm 8.5mm 2.7mm 8mm 2.5mm 8mm 2.3mm  
Puglisi mandolin: 28                  
Il Globo mandolin: 28                  
Bouzouki: (Irish) 36mm   3.5mm 5.75mm 3mm 5.5mm 2.75mm 5.25mm 2.5mm  
Mandola: (Tenor) 32mm 2-3mm 3mm 5.5mm 2.75mm 5mm 2.5mm 5mm 2.5mm 2-3mm
Mandriola: 38mm   5.5mm 5mm 5mm 5mm 4.5mm 5mm 4.5mm  
  Note that mandriola strings are in 3s, so the width is between the outermost of the 3 string course.