Classical Guitar - Nut Slot Heights

[Robin, Wales]

Quick question. I have found a (free) 3/4 size classical for a friends daughter to learn on. Do I set the nut slot heights the same as for a steel strung acoustic (just a hair above fret height) or is there something else I should know?

[John Arnold]

The same. The logic behind setting the nut height is universal.
Classicals, especially cheap ones, often have high nut slots because nylon strings are inherently easier to play, and intonation doesn't suffer as much as on steel strings.

[Robin, Wales]

Thanks. The strings at the nut are high enough to hang your washing from at the moment!

[coder]

Some people may disagree, I like to dial them in to be the same heigth as the fret heigth. I view the nut slots as a zero-th fret, that is why.

The method to dial them in: You need a steel thickness gauge. Find a combination to match the heigth of the frets, and put the thickness gauge on the fingerboard next to the nut. This will prevent you from filing the nut slots too deep. File the slots until you hit the steel thickness gauge.

It helps to have a set of good nut slot files to roughly match the string diameters. If you expect to do this more than once, IMO it is worth investing in a set of Japanese UO-CHIKYU, they look like oversized nail files, and cut really fast.
Be careful of the slot angle and direction, use the strings as your guide.
Las time I bought a set years ago they were 70-80$, I think they more like $110 now, but well worth it. The string gauge they are meant for is printed on them, and there are different sets for different gauges. With a bit of creativity, you can get around this, for example you can pair 2 of them together for making a differen width slot.

The alternative is a set of small rod-like files, which cut much slower, although these are also cheaper.

It makes a surprising amount of difference in playability, and most guitars I come accross have the slots set up too high. Very common problem on new, factory made guitars.

[redir]

In theory the nut slot height should be the exact same height as the fret in front of it. IOW it's just another fret. On SS guitars I like to make the bass strings nut slot height just a bit taller for players who like to bang on the open chords. But for a classical guitar they would be fret height across.

[RogerHaggstrom]

I use a bit thicker hair on the nylon strung guitars due to the wider vibration from the soft strings. For the bass E string, I use 0.45 mm for steel strings and 0.50 for nylon strings (my feeler gauges comes in 0.05 mm steps). All heights above the 1st fret on a steel string guitar is made about 0.05 mm higher than a zero fret would give with a normal height at the 12th fret. The technical term is "a hair higher" for steel strings, for the nylon strings "two hairs higher" :-)

Actually, the string height above the 1st fret is a function of the string height at the 12th fret. With a very low height at the 12th fret, the height above the 1st fret have to be a "hair" higher not to have a back buzz. With a really high string height at the 12th fret, the height above the 1st fret can actually be a"hair" lower than the height given by a zero fret.

[Russ C]

The relief in some necks may manifest more in one region than an other. If that happens to be the first few frets the nut could even be lower than fret height as there is more angle there than needed.
I would choose to stick with fret height at least for the feel of consistency if nothing else but that situation (not probable it should be said) can be a safety margin if you’re concerned about your ability to get it just right.
My post really is splitting hairs though.

[Bob-Chicago]

Originally Posted by coder

Some people may disagree, I like to dial them in to be the same heigth as the fret heigth. I view the nut slots as a zero-th fret, that is why.

Are you serious? did you write that wrong? Did I read it wrong X times? With zero clearance over the first fret you’ll get nothing but buzz from any open strings.

[Rudy4]

This will work for you.

[John Arnold]

Originally Posted by Bob-Chicago

Are you serious? did you write that wrong? Did I read it wrong X times? With zero clearance over the first fret you’ll get nothing but buzz from any open strings.

Yes, you read it wrong. With the nut at fret height, you don't have zero clearance over the first fret. If you capo on the first fret, your new 'nut' is at fret height, and you don't have zero clearance over the second fret.
I never measure action at the first fret. Setting the nut at fret height makes it unnecessary.

[Mirosh]

"It helps to have a set of good nut slot files to roughly match the string diameters. If you expect to do this more than once, IMO it is worth investing in a set of Japanese UO-CHIKYU, they look like oversized nail files, and cut really fast."
---- Coder, above

I recently bought a set of 6 of these. The vendor was Plaza Japan. Ordering was easy. I put them on my Visa card. Net cost was $72.79. Delivery was within a week or two. My first real nut files - I am very happy with them.

[nikpearson]

The following measurement are for the space between the bottom of the string and the top of the first fret with each string fretted at the 3rd fret.

1st string - 0.05 mm
2nd string - 0.1mm
3rd string - 0.2mm
4th string - 0.1mm
5th string - 0.2mm
6th string - 0.25mm

These allow for robust playing on all strings and typical classical action of 4 mm on the 6th string and 3 mm on the 1st string, both at the 12th fret.

Of course you can have a significantly lower action at the 12th fret if you play more lightly, but for most concert players these work well; most of us don’t realise quite how much energy a good player generate, especially with their thumb.

By way of comparison, my measurements for steel-string are as follows:

Low E: 0.15 mm
A: 0.1 mm
D: 0.1 mm
G: 0.1 mm
B: 0.1 mm
High E: 0.05 mm

To arrive at these figures I use feeler gauges and nifty little device made of 0.10 mm thick sheet spring steel stiffened sandwiched between Corian or wooden scales. With about 80 mm of length the spring steel mini straightedge can be rested in the slot and on the 2nd fret. You then measure the space between the top of the 1st fret and string bottom, just as you would with the string. This allows me to quickly, but precisely, bring the the nut slot down without having to lift the string in and out repeatedly. Credit for the device should go to (former?) forum member Murmac. After purchasing one from him, I’ve made a few of my own for luthier friends.