Correct Nut Slot Height
So you've been woodshedding for weeks, trying to cop your favorite Grisman lines, and all you have to show for it is a sore left hand. Not surprising if your mandolin is setup poorly, and most that I see are.
With double course high-tension strings, a proper mandolin setup is critical to the accuracy and enjoyment of playing. A setup is a very personal thing, but no matter how you like your action, there are several important points to consider when setting up a mando: string gauge, neck relief, bridge radius, action height, intonation and string height at the nut. We’ll go through each, and have a look at how they are interrelated.
The truss rod, the nut slot depths, the bridge saddle radius, the fret tops condition and the playing style all have a role to play in the final string height achievable without fret buzz. Truss rod setting was covered previously, if you need to refer back. Final nut height has a huge impact in the overall dynamics and perceived tension of the guitar. I researched and read a lot of info on the web and TGP about recommended nut height as compared to the height of the frets and most info recommends it should be just over that height. Say about.006.010 some suggested almost fret height. The ideal nut slot height, in terms of playability, is subjective — much like string action height at the bridge. Some players like the slots to be cut up a little higher (like slide players), and some players want them cut down as low as possible so the guitar plays very easy with no fight.
Keep in mind that this is not a step-by-step lesson in how to do your own setup, but should serve as an overview to help you learn how the different adjustments can make your mando play great.
Choosing Strings
The easiest way to affect the playability of your mandolin is with your strings. String gauge will have a huge effect on the feel and playability of your mandolin, with lighter gauge strings being easier to fret than heavier gauge strings. The measured difference between the lightest and heaviest string sets seems small, but on a double course instrument with high string tension, it makes a big difference. Strings are cheap, so experiment until you find what you like.
Neck Relief
After you have selected your string gauge, neck relief will be the first thing to check. Relief is the amount of forward curvature in the neck along the string path. Relief is needed to make space for the oscillation of the string, which is greatest at its mid-point. A mandolin needs very little relief.
One to two thousandths (.001) of an inch, measured at the sixth fret, with the string fretted at the first and twelfth, works well for most players. This is about the thickness of a piece of paper, so not much at all. Too much relief and the action can be high, yet buzzy, mid neck. Too little relief and there can be fret buzz in the lower positions.
Bridge Adjustments
Once you have your relief dialed in, you can move on to the adjustments at the bridge. The bridge takes care of three main things:
- string radius
- action height
- intonation
String Radius
Most mandolins have a flat fingerboard across the fret as opposed to most guitars, which have an arch to the fret. For even playability across the fretboard, the radius of the strings at the bridge should match the radius of the frets.
With this in mind, if you rest a straight edge across the strings, just in front of the bridge, all eight strings should touch the straightedge, with no high or low strings. This is adjusted by filing the string slots to even out the strings.
Action Height
All set? Good. Now for the action height. If you were wondering what the little wheels under your bridge top do, this is it. The top of your bridge sits on those wheels, which move up or down when you turn them, raising or lowering the action. I measure action, which is the height of the strings off of the frets, at the twelfth fret, with the string fretted at the first fret. You can use a Stew-Mac string action gauge, feeler gauges or a little ruler to measure the string height.
For most of my customers, I have found that fifty thousandths (0.05) of an inch on the bass strings, and forty thousandths (0.04) on the treble strings is good. This height will allow a clean tone with comfortable playability. If the action feels too stiff, lower the bridge. If you have string buzz, raise it.
Correct Nut Slot Height Calculator
Intonation
Last bridge adjustment: intonation. Intonation is the adjustment that allows the fretted notes to play in tune with the open string. Check this by tuning your open string, then fret at the 12th fret and see if the fretted octave is in tune. If the fretted note is not in tune with the open string, you adjust it by:
- moving the bridge towards the neck if the fretted note is flat
- moving the bridge away from the neck if the fretted note is sharp
Every note may not be perfect, but with a compensated bridge top, they should be very close.
String Height At Nut
The Nut
There’s one step left, checking string height at the nut, and it has an enormous impact on how the mandolin plays in the first position. If the strings are too high at the nut, it’s really tough to fret, and the intonation in the first position can be sharp. If the strings are too low, they will buzz when played open.
String height is adjusted by filing the nut slots until the strings are at the proper height. I check string height by measuring the distance between the top of the first fret and the bottom of the string using a feeler gauge. I shoot for twelve thousandths (0.012) of an inch clearance under the G and D, and ten thousandths (0.010) under the A and E.
You’re all done. Broken down into steps, a mandolin setup is not that complicated and, done properly, will dramatically increase your enjoyment of the instrument. One thing to remember, if your fretwork is bad, you need to have that addressed in order to get the best playability out of your instrument. A poorly setup mandolin is brutal to play, but one that’s setup correctly is a joy. Now go try that Grisman tune again. Bet you nail it this time.