Puzzling intonation issue: first 4-5 frets note sharp

[Dave Richard]

Recently, three different guitars have come to me, the owners complaining of sharp intonation on the first 4-5 frets. All newish electrics, one Telecaster, one Gibson ES-137, one Epiphone. All three have what I consider very tall frets(.053" on the Gibson and Epiphone).

I checked the nut slot, and 12th fret intonation, and adjusted where necessary. On the Tele, I installed a NOS Earvana compensated nut(but the owner was not happy with the result). On the Epiphone, my lowering the nut slots helped slightly. The Gibson needed neither adjustment, but intonated sharp.

The Tele owner uses extra lights(with the .009" first string), the Gibson/Epi owner uses .011"sets. 

I went so far as to order a Gibson fret scale from Stewmac, to check the fret layout on the Gibson: the fret layout on the Gibson does not match any of the three 'short' scales on the scale(but then, neither does the 1951 Gibson LG2 I also have in my shop at the moment).

I am puzzled by this problem, and do not have a good answer. I have tried to research this issue online, and I'm aware this is a common complaint on several guitar forums.  Has anyone here dealt with this complaint, and found a solution?

[Greg Mirken]

Sounds like the nut to first fret distance is just too long; an issue I have encountered on Gibson guitars. If you capo at the first fret and tune it, is everything ok from there up? If so just saw a little off the fingerboard and make a new nut.

[Roger Häggström]

Yes, move the nut forward. You can test the intonation for each string with a small piece of bone or metal to move the intonation point forward and get a nice mean value to move the nut - should be around 1 mm.

There is also possible that the 4-5 first frets are misplaced. Stewmac have a fret calculator you can try, you need to know the open string length the original frets are supposed to follow.

[Nathan Laudenbach]

That sounds like the Ovation problem. One Ovation comes in for repair, and more follow.

[Dave Richard]

Hi Greg and Roger, thanks for your replies. I'll try the capo & recheck the intonation on each fret. Have both of you actually corrected this issue by trimming the fingerboard, and/or comensating the nut?

[Greg Mirken]

Yes, I have actually done this on a Gibson guitar. It was several years old, and had always had poor intonation that nobody could correct, because they had all fiddled with the saddle.
If the distance from nut to first fret is A, first to second fret is B, and second to third fret is C, then C/B=B/A. Take accurate measurements and solve for A. This is the theoretical position for the nut. See how far off it is.

[Roger Häggström]

Yes, I do nut & saddle compensation for each individual string on every old parlor guitar I restore. I have probably made close to 50 nut compensations by now. Compensating the nut gives me a chance to get "perfect intonation" on two spots on the fretboard, I chose the 3d and the 12th fret.

After measuring all the intonation points in the nut and saddle using a stobe tuner, the fretboard is cut typically 1-2 mm at the intonation point closest to the 1st fret. The other 5 individual intonation points are then milled back in the rectangular nut, I don't like the jagged appearance of a shelf nut...

Using the mean intonation point measure to cut the top of the fretboard with a straight nut will go a long way.

[Dave Richard]

Great, thanks again. I'll muse awhile on this one, see if I can ID the fix.

[Harry G Quattlebaum]

Playing technique also affects intonation, especially with tall frets and light gauge strings. If your customers play with a heavy touch, they can throw the strings out of tune, in the same way that players can make even a medium to high action set up buzz if they pick downward into the top of the guitar. Not saying that's the issue here, but it's something to consider. I'd want to carefully watch each of them play their guitar as part of  troubleshooting the problem.

[Walter W Wright]

i'm not sure that i've ever in all my years of doing this ran into a production factory-made guitar where the nut actually needed to be relocated!

(that includes the ridiculously over-compensated earvana and the whole buzz feiten thing, which i was an official installer for back when people bought into that)

it's far more likely the nut slots are just too high, maybe combined with tall frets and/or thin strings on a guitar owned by a player used to death-gripping an acoustic with big strings and little frets.

i'm using a sonic research turbo-tuner, which is a real analog strobe tuner and super-accurate, really more accurate than the guitar itself is capable of being, and (given good frets and proper setup) with the nut slots down where they belong the first few frets will intonate just fine.

[Roger Häggström]

Good call. The string height at the first fret and also the 12th fret are major player in the intonation game. So is the fretting force. I just took those for granted... But even with a perfect setup, intonation will almost always be better if the nut is moved closer to the first fret. How much to move the nut is depending on the guitar itself, the open string length and the stiffness/thickness of the strings.

Normally, a good measure for the height at the first fret is the height the same height zero fret as the rest of the frets gives. If the string height is really, really low at the 12th fret, the string height at the first fret have to be a bit higher not to have a back buzz. If the string height at the 12th fret is really, really high, the string height at the first fret can be lowered.

[Greg Mirken]

Walter, I can assure you that I have encountered, and corrected, this exact issue on a Gibson acoustic guitar, using the method I described. I was given the job after several other luthiers were unable to make the guitar intonate correctly; they probably assumed that the nut was placed correctly, so they attacked other factors. This is the only time I have encountered a misplaced nut that was certainly a manufacturing screw-up from a major manufacturer.

On a slightly related note, when I was working at Dobro in the 70s, the fret slots were cut by a giant gang-saw with blades separated by numbered brass spacers. They handed me a stack of boards to inlay and fret, and I noticed that two fret spaces, up around 10 or 11, were switched, making one fret badly out of position. I told Ron that these were not usable, and after I showed him the problem he countered with "Well, these are just for squareneck guitars anyway." I declined to work on them, but I don't know if they threw them out or found a way to use them. So don't assume whoopses can't happen!

[Dave Richard]

To clarify: the nut slots are NOT too high. 

The owner keeps .011/set on the guitar, so the strings are not too light.

And it's not a question of player technique. When I myself play the instrument, and no matter how lightly I fret the guitar, those first 4-5 frets note significantly sharp.

Another factor, which may not be relevant(but seems so to me): As mentioned, I bought a StewMac Gibson fret scale to check the fret layout. This Gibson matches none of the three 'short' scales, except: when I place the 24-9/16th scale on the fingerboard, I can line up the nut mark, and the 12th fret mark, but...all the other frets are off. From the 1st to the 8th fret, they fall 'short' of the marks(toward the nut), from 9-11 they move back toward the marks, and from 13-22 the frets move away from the ruler marks, toward the bridge. It seems to me, that if the nut, and the 12th fret, align with my StewMac fret scale, that would make it a 24-9/16th scale...except all the other frets are off. ???