Action Height at First Fret

[trochilinae]

Here are a couple of informative sites to look at:

http://bryankimsey.com
Lutherie page.


and

http://thbecker.net/guitar_playing/g...p_page_01.html

[charles Tauber]

Originally Posted by NEGuy

I tried this procedure on my last string change (it certainly makes sense), and, frankly, I am dumbfounded by the results.

I used a StewMac straight-edge between the 2nd fret and the nut slot of the low E string (since there is obviously no string under tension during a string change, so I cannot use a string), and I saw no clearance between the straight-edge and the 1st fret.

And that is the source of the problem. The neck changes shape when under tension. That is also the reason why, whenever possible, to adjust the truss rod with full tension on the neck AND adjust the truss rod prior to setting the string height at the nut/first fret. The bow in the neck affects the string height at the first fret. Note: the purpose of the truss rod is not to adjust the string height at the nut/first fret. It is to adjust the bow in the neck, the amount of which has an influence on the string height at the nut/first fret.

Always adjust the string height at the nut when the neck is in its as-played geometry. The easiest way to accomplish having the neck in its as-played geometry is to do the adjustments with full (or near full) string tension on the neck. (Stewmac sells an elaborate jig/work board to hold a guitar neck in its as-played geometry while the strings are off. Sounds nice in theory. No, I don't own one and don't see one in my future.)

Greatly exaggerated, but it illustrates the change in geometry:

I might be confused, but wouldn’t you want the clearance to *decrease* as you go from the bass E string to the treble E string?

Yes, of course. Apologies for the poor communication.

Both John and Frank, of course, know of what they speak. The methods they describe work equally well: it's just a matter of preference which you prefer to employ.

[NEGuy]

Originally Posted by charles Tauber

And that is the source of the problem. The neck changes shape when under tension.

Ah, makes sense – thanks very much for the insight, Charles!

Originally Posted by charles Tauber

Both John and Frank, of course, know of what they speak. The methods they describe work equally well: it's just a matter of preference which you prefer to employ.

I'm sure theirs is a fine method, and, as accomplished luthiers (like you), I’m sure they use the method well.

I guess I was looking for a method to check *before* stringing up the guitar and bringing the neck under tension (thus the use of the straight-edge when no string under tension was available). Your method seems good for this.

I can then use their method as an "after-check."

Two quick final questions?

1.

Originally Posted by Brhibler1

I do it this same way, but add .01 to my height.

Given that Brhibler1 seems to get a successful set-up by adding .01 to the fretboard height (post #9), then, if I want to be a bit on the conservative side initially, it seems that starting at this level for the low E to possibly a shade less on the high E should be good, huh?

2.

Originally Posted by charles Tauber

In my opinion, the easier way to set the string height at the nut is to measure the height of the first fret . . .

I know there are a number of ways to measure the height of the first fret – I was just wondering how you did this in your procedure.

Thanks again for all the helpful posts.

(Some very nice instruments on your site, Charles, by the way.)
.

[charles Tauber]

Originally Posted by NEGuy

I guess I was looking for a method to check *before* stringing up the guitar and bringing the neck under tension (thus the use of the straight-edge when no string under tension was available). Your method seems good for this.

I've never set the final string height at the nut without full (or near full) tension on the neck. In theory, I suppose it would work, but I don't recommend it. One or two thousandths is the difference between perfect and buzzing at the first fret. I check my work as I go, adding or subtracting based on the results of the previous string.

Given that Brhibler1 seems to get a successful set-up by adding .01 to the fretboard height (post #9), then, if I want to be a bit on the conservative side initially, it seems that starting at this level for the low E to possibly a shade less on the high E should be good, huh?

Yes. Note it is added to the measured first fret height: the height of the crown above the fingerboard.

I know there are a number of ways to measure the height of the first fret – I was just wondering how you did this in your procedure.

I take a 6" ruler and lay it parallel to a string so that it sits on frets 1 and 2 and extends over frets 3, 4 ... I use either a stack of feeler gages or a pin gage and use the appropriate size/stack of gages that just fits between the surface of the fingerboard and the bottom of the ruler. The ruler positioned like this, but at the first fret - what is being measured in the photo is the string height from top of fret to bottom of string, using the vertical scale on the end of the ruler:



Others may prefer a vernier calliper for the measurement, but I find the ruler and gages to be quick and easy and is the same measuring device used to gage the nut slot depths. That means I don't need to measure with one type of device, then switch to another type of measuring device to gage the slot depths.

Keep in mind that if the frets have been dressed, the frets may be a different height towards one edge of the fingerboard versus the other.

I add about .006 to .008" - occasionally more for short-scale instruments or those that feel very loose - to the measurement, stack the appropriate gages to that thickness and then use the gages as a stop for filing, as seen below. Note that all strings are to full tension, but for the string belonging to the slot I'm filing. That string is at about 3/4 or so full tension.

(Some very nice instruments on your site, Charles, by the way.)

Thank you.

[NEGuy]

Charles,

Many thanks for sharing your considerable knowledge and experience – really, I very much appreciate your time.

I know I seem like a dolt here, but I can give you the reason why I was doing all of this while the strings were *not* under tension.

I have a custom-built guitar that is great in every way, but the action was just a bit too low. The luthier who built the guitar accommodated my distance from him and arranged a set-up with a more local luthier, but this did not go well (it happens).

I brought the guitar to another luthier who fixed everything beautifully, but one thing he did was to install a shim underneath the nut so as not to have to make a new one (picture below).

So you see my dilemma: I cannot shave the shim down while the strings are under tension.

I guess I’ll decide whether to make the slots deeper (with your expert method) or pop the nut off (as I have done the past two times) and lightly sand just a little of the shim each time between string changes until it comes down to the proper height.

If you (or anyone else) has suggestions here, they would be most welcome, and, again, thanks for the short course in luthiery.
.

[charles Tauber]

Originally Posted by NEGuy

If you (or anyone else) has suggestions here, they would be most welcome, and, again, thanks for the short course in luthiery.

Overview:

Measure what you have; subtract from that what you want to have; remove the difference from the shim.

Details:

With the strings at full tension, measure the distance from the surface of the fingerboard to the bottom of the strings adjacent to the nut. I'd use feeler gages for that. Measure the height of the first fret using the method previously described.

Subtract from the first measurement - the current height of the strings above the fingerboard at the nut - the second measurement - the height of the first fret. Remove the strings and the nut. Remove the shim. Measure the thickness of the shim at both ends. I'd use a vernier calliper for this. Remove, by whatever is your favourite method - I'd use a hand plane if the shim is thick enough to allow that - the amount you calculated. Reassembly it all and you should be "done".

This assumes that the wooden shim does not compress and change thickness under string tension. It is unlikely that it compresses enough to matter.

This also assumes that the individual string heights are already at the correct proportional heights, one to the next. If not, you'll need to adjust the height of each individually, accordingly. More than likely, the assumption is false.


Were it me, if the shim is well made, I wouldn't bother with it. I'd simply cut each existing slot to its required depth, as is. The shim is a red herring. Consider it a part of the nut.

[NEGuy]

Originally Posted by charles Tauber

Were it me, if the shim is well made, I wouldn't bother with it. I'd simply cut each existing slot to its required depth, as is. The shim is a red herring. Consider it a part of the nut.

Ah, but you are an accomplished luthier.

Seriously, I think the "red herring" of the shim has afforded me the luxury of not having to tackle the task of cutting the nut slots.

But, alas, I guess I'll get a set of needle files and give it a go. It's not as if I'm scalloping the top bracing.

Thanks again for all your time, Charles.
.

[Frank Ford]

Shimming the nut is usually a simple matter of sticking something underneath. In my experience, the choice of shim material is entirely cosmetic, if the nut is glued normally to the end of the fingerboard.

My favorite is a sticky mailing label:

http://www.frets.com/FretsPages/Luth...m/nutshim.html

The idea is to raise the nut just enough so that the lowest string is set correctly, or thereabouts, and then file the slots for all of them appropriate height, one at a time as needed.

I guess even the smallest problem can be overthought to the point it reaches epic proportions. . .

[rick-slo]

In regards to setting string height at nut while strings under tension, allow for the lowest alternate tuning tension you use with any frequency.

[NEGuy]

Originally Posted by Frank Ford

Shimming the nut is usually a simple matter of sticking something underneath. In my experience, the choice of shim material is entirely cosmetic, if the nut is glued normally to the end of the fingerboard.

My favorite is a sticky mailing label:

http://www.frets.com/FretsPages/Luth...m/nutshim.html

The idea is to raise the nut just enough so that the lowest string is set correctly, or thereabouts, and then file the slots for all of them appropriate height, one at a time as needed.

I guess even the smallest problem can be overthought to the point it reaches epic proportions. . .

Oh, Frank, I don’t think you have a true sense of this problem – it is truly epic.

Seriously, I’m not sure if you’re referring to my handling of this issue or the former luthier.

I do think the former luthier could have done something like what you suggest in your link, and I was planning to do something like this myself if I took things down a bit too far (only I was thinking of brown striping tape to match the rosewood of the guitar rather than mailing labels to match the bone of the nut).

I actually don’t mind at all that I have encountered this problem, however. With the thread here as well as the one I initiated on UMGF, I think I now know the intricacies of 1st fret nut action from every angle.

I worked in enterprise-level IT for quite a number of years, and it seems that when an IT project went smoothly, I learned nothing. But when things went wrong – well, that’s when the real learning began.

Ditto for guitar set-ups, I think.

I would like to do all set-up type activity myself in the future, and I guess one has to start somewhere.

If anyone has any recommendation for needle files, I’d appreciate any suggestion.

I doubt that one has to pay this much for such files if one is a non-professional:

http://www.stewmac.com/Luthier_Tools...Nut_Files.html

Thanks again to all.
.

[NEGuy]

Originally Posted by rick-slo

In regards to setting string height at nut while strings under tension, allow for the lowest alternate tuning tension you use with any frequency.

I’m a EADGBE kinda’ guy.
.

[Frank Ford]

Originally Posted by NEGuy

If anyone has any recommendation for needle files, I’d appreciate any suggestion.

The classic nut file replacement for "casual" use is the set of really cheesy files sold in welding shops as "torch cleaners."

Buy-it-now on eBay for 6.99, including shipping: http://www.ebay.com/itm/Welding-Torc...item27af68a0aa

Sure, they're lousy files, but they can do the job if you're wiling to suffer just a little. . .

I've done and taught setup work for most of my life now, so, you're right - I may be looking at things from an experienced perspective. However, as a teacher of rank newbies, I never have a problem getting them going comfortably in very short order, with no measuring of anything needed.

In our shop there has never been a need to measure. It's always visual, just as I described, no matter who of us is doing the job or inspecting the instrument. High school summer interns get it the first day, and are generally able to judge nut action competently. Learning to set it quickly and easily comes a bit later, and with practice.

Beginners sometimes cut the nut action too low by accident, and sometimes are timid about approaching the lowest logical point, so they leave the action a bit high. That kind of judgment comes with practice, and it can take a little while. The worst and by far the most common serious problem beginners make is scratching the peg head surface with the end of a file. Being careful with that aspect of the process takes a while to become automatic, so I always suggest they use a bit of protection - cardboard, tape, or whatever, in that area at first.

Fingerboards are too often unevenly sanded with a bit of fall-off right where they contact the nut, so about the LAST thing I would consider is actually measuring string height at that position.

[John Arnold]

Fingerboards are too often unevenly sanded with a bit of fall-off right where they contact the nut, so about the LAST thing I would consider is actually measuring string height at that position.

That is my take on it, as well.
The only time I would even consider it is when I personally have leveled the fingerboard, but the 'eyeball' method works just fine.

So you see my dilemma: I cannot shave the shim down while the strings are under tension.

I don't recall a time when checking the nut height on an unstrung guitar using a thin straightedge gave a false reading, but most of the guitars I work on are older, and have thick necks that are pretty rigid. In other words, they don't move a whole lot when going from strung to unstrung. To tell the truth, I still don't understand why some neck movement would be a problem...unless the straightedge being used to check it was way longer than necessary. After all, if neck movement gives a false nut height, it will also give a false first fret height.

The one exception to this is when the slots are vee-shaped, rather than round- or square-bottomed. In that case, the string will actually be higher than the bottom of the slot, as checked with the thin straightedge. But that is easily remedied with rounded nut slot files. IMHO, vee-shaped slots are a bad idea, since they are susceptible to string binding during tuning.

The thin straightedge I use for checking nut slot height is nothing more than the back edge of a thin razor saw blade. The kerf is about 0.012", and the body of the blade is 0.010" thick. I use the same blade to cut 'test' slots in the middle of the string slot, as a gauge for the action. My procedure for cutting nut slots is simple....saw the thin test slot until it is level with the tops of the frets. Height of this slot is checked with the back of the razor saw blade, by simply flipping it over. Once the test slot is done, I go back and widen the slot with a nut file, until the test slot disappears. Voila....the slot is done....without ever checking the height with a string.

[NEGuy]

Originally Posted by John Arnold

I don't recall a time when checking the nut height on an unstrung guitar using a thin straightedge gave a false reading, but most of the guitars I work on are older, and have thick necks that are pretty rigid. In other words, they don't move a whole lot when going from strung to unstrung. To tell the truth, I still don't understand why some neck movement would be a problem...unless the straightedge being used to check it was way longer than necessary. After all, if neck movement gives a false nut height, it will also give a false first fret height.

The one exception to this is when the slots are vee-shaped, rather than round- or square-bottomed. In that case, the string will actually be higher than the bottom of the slot, as checked with the thin straightedge. But that is easily remedied with rounded nut slot files. IMHO, vee-shaped slots are a bad idea, since they are susceptible to string binding during tuning.

The thin straightedge I use for checking nut slot height is nothing more than the back edge of a thin razor saw blade. The kerf is about 0.012", and the body of the blade is 0.010" thick. I use the same blade to cut 'test' slots in the middle of the string slot, as a gauge for the action.

I have no experience in this area at all, but I could understand how, given the lack of any tension in the neck, there could be a difference of some thousandths of an inch (i.e., Charles’ graphic above – although I realize that the depiction is greatly exaggerated).

But, again, I do not have the experience in this area that you do.

I didn't have a good straight-edge to use, and I wanted to ensure that I had something that was indeed straight and quite rigid, so I used the StewMac 18” straight-edge.

Possibly this was a bit too long?



Seriously, I realize that it was *way* too long, but the excess length seemed to be harmlessly protruding beyond the headstock.

Originally Posted by John Arnold

My procedure for cutting nut slots is simple....saw the thin test slot until it is level with the tops of the frets. Height of this slot is checked with the back of the razor saw blade, by simply flipping it over. Once the test slot is done, I go back and widen the slot with a nut file, until the test slot disappears. Voila....the slot is done....without ever checking the height with a string.

If you check this thread again, then possibly you can answer this:

Are you stating above that you cut the nut slots to precisely the distance above the fretboard as the frets?

No extra clearance?

If so, then I guess the height of the bridge gives you that little bit of clearance at the 1st fret to avoid any fret buzz?

Thanks again for the response.
.

Originally Posted by NEGuy

...Are you stating above that you cut the nut slots to precisely the distance above the fretboard as the frets?...

I'm not John, but no extra clearance is needed. Do you have extra clearance when you fret a string? No, it is at fret height by definition. There is no reason the nut can't be the same.