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Just measured my LMI preslotted 24.9 fingerboard. Distance from nut slot to 12 fret is 12 7/16 or 12.4376. That makes the actual scale length 24.875. Is this what it should be?
Second question: how many of you shave 1/32 off nut end for compensation? A respected luthier suggests doing this.

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A higher purpose for wood.
Rich Smith
Issaquah, WA

I have LMI's scale break down at home but in therory if the scale is 24.900 using the 12 root of 2 the 12th fret should be 12.450. If your LMI fretboard is cut with the 12th at 12.438 (12.4375 rounded up to the nearest .001) then in dead the true scale of your fretboard is 24.875.

Now on the zero fret or nut compensation 1/32" (.03125) is a bit much .02" is the Max I use.

To me thats really 24.9 - here is what I think is going on. If you are measuring 12.438, then there is 12 thou missing from the true 12.450 - I figure thats half the width of the blade they use, and its cutting dead centre. Forget the nut to 12th fret - measure from some other frets to 12 and see what you get relative to a 24.9 theoretical measure.

As far as comping the nut goes, unlike Mike, I use about 1mm, which is 40 thou. Works great for me, regardless of scale length (25.4, 24.9, baritones,MSfretboards). I actually measured a factory Feiten Dean Dimebag with a locking Floyd nut that a studetn brought to replace the neck on, as the headstock had totally snapped off - it was comped forward exactly 1mm.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

I just comp the nut half the saw kerf so I finish at the edge of the slot that represents the nut, so about .0123" or so. I comp the saddle about .150" at the other end for the two scales I usually use. It seem to intonate pretty well.

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Tickle your guitar daily, and it'll tickle you back.

The actual scale length the frets are spaced to can be easily calculated by fret to fret measurement (1st to 13th, 2nd to 14th are easy ones for example), but the likely weak point is going to be accuracy in your means of measurement (I assume you're using a regular scale/rule). My guess is that it is a 24.9 scale board, compensated .012" at the nut. Either way though, application is the same. Nut to 12th x2, +compensation. You could certainly call LMI if you want to know their intentions with the spacing. I think .012" is fine, but I wouldn't go any further.

Tony, that's interesting that you found one compensated .040". I've measured out several Washburns, both US made and import with the BFTS sticker (including a US Dimebag Darrell model a few months back), and all of them that I've seen have had no nut compensation at all. Straight up conventional spacing, with the decal being the only Feitenized part of the whole instrument. They must have changed to actually implementing the BFTS, though I believe it should have been .030". For me, .040" would be far too much nut compensation.

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Eschew obfuscation, espouse elucidation.

Like the gibson scales the quoted Martin 24.9 scale is nominal, what you have is correct.

LMI normally sends out a scale set up scedule with each pre serviced fretboard that breaks down each fretposition for both nuted and zero fret set up. helpfull info to know exactly how the scale positions were arrived at.

Best I can tell the first fret is already compensated because the other frets appear to be in the correct positions. Thanks for the responses!

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A higher purpose for wood.
Rich Smith
Issaquah, WA

Be careful how you phrase things - by saying that the first fret is compensated, you would be indicating that the nut to 12th is correct for the scale length the slots are located by, but the 1st fret slot is moved toward the nut end and further away from the 2nd fret. I assume this is not what you meant? Compensated nut is very different from a compensated 1st fret.

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Eschew obfuscation, espouse elucidation.

I guess its all what works for you - I have about 100 guitars (mine and students) all with the 1mm nut comp, and they play just fine. I wouldnt think one could hear the difference in 30 to 40 thou of compensation - 10 thou is nothing - besides, its easy to put it back, simply angle back the front edge of the nut itself - but adding it on after the fact is tough.

anyone here ever do Earvana nut retrofits - we did one on one of my students 70s strats, that was really aweful in open postion - the earvana moved the G string break point forward 4mm - yes, 4mm, (the others all moved forward some as well) and I couldnt believe how well it played after that - the tuner even confirmed how close the notes were compared to the stock Fender position on that guitar.

Dont always assume that comping something means moving it towards the nut - first fret comp might just as easily be towards the 2nd fret too !!!!

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Tony, so if you can't hear the difference with 1 mm of compensation - should I bother?

_________________
A higher purpose for wood.
Rich Smith
Issaquah, WA

Math? What math?

Get yourself a something like a saddlematic and you won't look back. Intonation is perfect every time!

Dave

I don't believe Tony was saying you wouldn't notice a difference between 1mm and no nut compensation, but rather referring to .030" vs .040".

Here are some comparisons if you're interested. I calculated based on a 24.9" scale length, with some generic (based on average measurements) saddle compensation figured in. The numbers represent deviation from standard nut and fret spacing, assuming all variables within the setup (most importantly nut and saddle height) were to remain constant. These deviations are all in reference to no nut compensation, but does not imply that as perfect - only using it as a reference.

Here are deviations for a nut compensated .040"



Here they are for a .030" compensated nut.



And here it is for .012"



(numbers are rounded to 1/10¢, so please disregard slight inconsistencies in the progression)

So if you found with your setups a standard layout that your 1st fret was consistently 2¢ sharp and the 2nd and 3rd frets just under 2¢ sharper than your goal, then bringing the nut in .030" would be great. If your upper frets were not at all flat or actually tending to ring sharp however, that .030" nut compensation would be detrimental in those regions. Likewise, if there were no problems with a normal layout by the time you reached the 4th or 5th fret, then the nut compensation could be adding corrections where none were needed. This is why I prefer to compensate the first few frets only, by moving the slots rather than the nut thus leaving the rest of the board unaffected. I should note however that when the nut is cut to what I consider proper height, I find compensating as much as 2¢ in the first frets to be excessive. Fifteen thousandths for the 1st, ten for the 2nd, and five to seven for the third is plenty in my experience.

Now you won't be able to hear a discrepancy of one, two, or even three cents in notes played consecutively. Played concurrently however, it can be enough to be heard in unison or octave intervals, or if they happened to be positioned to do something such as widen a third.

In all practicality though, just build it with what you've got and you'll be fine.

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Hi David,

Right - I am saying not much difference between 30 and 40 thou of forward nut comp, vs none.

the chart is interesting stuff .. being purely theoretical, does it take into account the microtonal sharpening of a note when fretted though ( I am thinking not) ??? say in a C chord, the 5th C, 4th string E and 2nd C are fretted, the G and E strings are open .... this is the whole basis of why I comp nuts in the first place - based on an old AL article ....


Dave (livermore) ... using a saddlematic may get the 12th fret (and higher) notes to be closer in tune, but wont have much of an effect at the nut and first few frets. As a percentage of the distance between frets, the nut is too far away, and as such, making a 15 or 20 thou change at the nut will affect the 12th fret much more than the first. Besides, who sets the saddlematic in the first place ???? what if you change scale lengths ???? Its being set based on what ????

guitars are funny things .... theory will only take you so far, then reality takes over. Guitar strings dont act like theoretical strings are supposed to, so we 'compensate' for their inadequacies - sorry for the pun.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

David, I like that last sentence since my fretboard is already slotted. Given that this will be my first guitar, I'll bet nut compensation will be the least of my worries.

_________________
A higher purpose for wood.
Rich Smith
Issaquah, WA

Tony,

Yes, you're quite right that the chart doesn't take in to account any of the real world nuances of playing. It's pretty much purely academic exercise in comparing theoretical differences, without factoring in the huge variables of the human hand. Honestly, I made this spreadsheet more as an excercise to learn how to work complicated algebra and logarithms in Excel. It does put comparisons in a neat easy to view format though, just so long as you view them with all it's limitations in mind. That's why I try to emphasize that the numbers do not represent deviation from correct, but rather from an established reference, and without any of the real world subtleties taken in to consideration.

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I'm gonna get in here cuz to me this is the stuff that counts.

REALLY!!!!

I just had a long conversation on another forum regarding this very issue. I just completed my first guitar and I used the standard 24.9 scale. I cut the board using Stewmac's template with a sled. All measurements were dead on according to scale length before the frets were put in...and they were as close as you could measure using a digital dial caliper going crown to crown on the frets.

I found that even after string heights were set at the nut I still would play a G or a C or a diminished C and it would make me 'scream like a girl'. On the tuner these individual notes were 10-15 cent sharp. I, unknowingly, compensated my nut by 12 thou when I set the board up just by starting the nut at the forward most part of slot that would represent the zero fret. Not enough. I am already working on my second and will compensate the nut to somewhere in the .25 thou range to see if I can settle the first three frets down.

One question for David Collins. If you actually compensate the 1st fret and the 2nd fret, do you leave the nut in it's theoretically correct position or do you move it forward? I could very easily compensate these first two frets by switching to a slot to slot measurment during my use of the slotting template. Would be very interested to know....I don't really like screaming like a girl!..

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There is no difference between the man that thinks he can....and the man that thinks he cannot.

If you're finding notes going that sharp in the first frets, then either your nut is still way too high or perhaps some other more serious problems. To compensate 10-15¢, you would be looking at moving a nut, fret, or saddle at least .150"-.200"!.

Two rules I suggest understanding and following for compensation. First, don't overcompensate for a bad setup. Many people seem to start compensating with their nuts still too high and end up overcompensating in my opinion, treating a symptom rather than the source of the problem. Any time you move a nut or saddle of course you effect all frets, in many cases in ways you may not have wanted to.

Second rule - don't try to overcompensate for temperament. Any time you try to sweeten one interval you will inevitably sour another. Don't try to flatten the major third in the open E chord by overcompensating the G at the nut, because then you'll sour chords like the A and Bmin chords (or whenever it has to act as a minor third against the D string, or major third against the B).

And when I say compensated nut of fret I mean just that. Everything is obviously only exists measured relative to the rest of the system, so if we want to discuss compensation clearly it's best to define everything in reference to a known constant. In this case the constant is the perfect theoretical spacing or 12th root of 2, with no compensation anywhere. Any time you refer to something being compensated, it should refer to that one point and it's deviation from our uncompensated reference.

So yes, when I refer to compensating a fret, I am moving that fret and that fret alone. Everything else including the nut is not moved. This way if I happened to measure everything else on my no-nut-compensation guitar as right on from the 4th fret and up, I can add compensation only where needed. Move the first fret, and I don't have to worry about altering anything at the 5th or 20th like I would if I moved the nut and saddle.

In your case though, where you mention 10-15¢, you should be looking at the setup first and not jumping to overcorrect with compensation. A more refined nut height will alleviate the need for most nut compensation in my experience.

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Eschew obfuscation, espouse elucidation.

Thanks for the effort in the charts David ... that must have been fun !!!!

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

David....after I made that post I got my guitar out and started looking closer at the string heights in the first fret. The B and G string could go down a little more. I have kept them like this because I have a heavy attack. Scared to death to get a buzz. This is the 3rd nut I have in this guitar. Not afraid to do the 20th nut...just trying to refine the existing one until refinement no longer gets me further down the road.

So...i am going to lower those strings a little more and see what happens. I would lean towards setup being the culprit just because it's my first. One of the most frustrating things is knowing that something needs to be done in the setup area...but NOT knowing what exactly to do. Couple that with the fear of screwing up something that may be right...and....it'll put your mind in a straight jacket. I wish I were tone deaf.

Chris

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There is no difference between the man that thinks he can....and the man that thinks he cannot.