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Mandolin Doctor
Setting Up Part 1
The Nut
One of the most mentioned issues in my post is the set-up….. or ‘how to achieve an easy playing action’. Given that there can be a variety of string choices, and you have a level fingerboard, work on setting up an instrument, falls into two main areas; the nut and the bridge. The set-up should place the strings not quite parallel to the fingerboard, at the optimum playing height. Too high, and it is impossible to play quickly, and hard work besides; too low, and you will have rattles and buzzes. In general I aim at 1.5mm between fret top and string bottom at fret 12.
Mandolins either have a nut or a nut-and-zero fret…. (the latter uncommon on US instruments, but not on European ones). The purpose of the nut is to stop the strings cleanly, keep the strings spaced, allow the strings to slide, and maintain optimum height above the frets. Where a zero fret is present, this should do the first and last for you. Where you have only a nut, you must set up the nut to do everything. I will assume we are making a new nut, so I cover everything.
Step 1: Choose a hard material for the nut and cut it to size. Bone is most often used.
If you are replacing a nut, cut it the same size as the old one, but a little taller. 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.
Step 2: Fit the nut foot carefully to the nut slot. They can be quite finely tuned by being rubbed on a piece of flat sandpaper. Finish the nut off to about 1mm above the fret height. 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 string positions must be marked out. 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. Exact spacing depends on the width of the neck at the nut.
Step 4: The next step is to start the string slots. Holding the nut in a vice, using 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, slots will need to be cut below the level of the frets, and angled down. If there is no 0 fret, cut no deeper than 1/2 mm above fret height.
Step 5: The slots need to be fitted to the individual string sizes. I tend to use purpose made saws, but a needle file and pieces of old or off-cut strings works too. The slot needs to be wide enough to fit the string with no room for vibrations within the slot, loose enough to allow it to slide smoothly. The front edge of the slot should 'stop' the string cleanly, hence the slots angled down towards the head. Use 4 old strings to try a test set up. If you are happy with size, fit and general string height, you can glue it in.
Step 6: Fine tuning. You will probably need to make small adjustments once the bridge is fitted, strings are on and fully tuned. I will tackle fine tuning in part 3, once the bridge is in place. I tend to do both together, as one affects the other.
NB. I have purposely avoided mentioning truss rods, as it would complicate the issue too much at this point.
Next time…..
Setting Up Part 1: the bridge
Tip by Dave Hynds, November 2007
