Recommended action height at 12th fret survey

Construction and repair of Classical Guitar and related instruments
Robert England
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Recommended action height at 12th fret survey

Post by Robert England » Fri Apr 11, 2014 12:17 am

I have a customer who thinks that 2.8mm at the 12th fret for the 1st string and 3.6mm for the 6th string is too high for a classical guitar and needs to be lowered. This got me wondering about what the established standards really are, so I did a survey of some of my guitar making books to see what the "experts" say. Here is a little essay that resulted:

What are the established recommended standards for classical guitar action height? This is a survey of recommendations published in a few books and manuals regarding this question. Items are listed in chronological order of publication. My comments are in Square brackets []. In addition to the citations here, I reviewed several other books (e.g. Irving Sloane, A.P. Sharpe, Roger Siminoff), where I could not find a specific recommendation for action height.

1. In the book, "How to Make a Classic Guitar", by Joseph F. Wallo, c. 1962, [apparently self published], p. 27, Wallo says, "Height of the first string at the twelfth fret should be 1/8 inch [3mm] and the sixth string should be 5/32 inch [4mm].

2. In the book, "Classic Guitar Maker's Guide", second ed., by H.E. Brown, c. 1967, pub. International Guitar and Import Co., Tulsa, OK, p. 42, Brown says, "The bridge saddle is now trimmed down so that when a string is pulled tight between saddle and nut the height of the strings at the twelfth fret will be 5/32" [4mm; this appears to be the same action for all six strings.]

3. In the book, "Make Your Own Classical Guitar", by Stanley Doubtfire, c. 1981, ISBN 0-8052-3833-6, pp. 106-107, Doubtfire says, "Measure the distance between the top of the 12th fret and the under surface of the first string -- it should measure 3mm. Do the same with the 6th string -- it should measure 4mm."

4. In the book, "Guitar Making Tradition and Technology", by William R. Cumpiano and Jonathan D. Natelson, c. 1987, ISBN 0-8118-0640-5, p. 372, the authors say, "For purposes of this operation [shaping the saddle height], approximate standard twelfth fret clearances on the classical (in sixty fourths) are: 10 9.5 9 9 8.5 8 [4.0 3.8 3.6 3.6 3.4 3.2 mm]."

5. In the book, "Things About the Guitar", by Jose Ramirez III, c. 1990, ISBN 84-87969-40-2, pp. 42-43, Ramirez says, "The action universally accepted for the classical guitar is 3 mm for the first string, and 4.5 - 5.5 for the sixth, measuring the separation between the back if [sic] the 12th fret and the lower surface of the string, that is, the space existing between the two objects, with the guitar correctly tuned."

6. In the book, "Making Master Guitars", by Roy Courtnall, c. 1993, ISBN 978-0-7090-4809-1, p. 306, Courtnall says, "The sixth string must be left slightly higher than the first. The final gap should be between 3.5mm and 4.0mm. The first string is less likely to touch a fret when it vibrates, so the final gap here can be 2.5mm to 3.0mm."

7. In the online Web based instruction manual, "Online Apprentice: 2002 Project: Segovia's 1937 Hermann Hauser" [was located at www.OnlineApprentice.COM, but this is gone now and replaced by a commercial "portal" site], by David Schramm, c. 2002, in Chapter 24, the author indicates that a "low" action would be 0.100" [2.5mm] and a "normal" action would be 0.115" [2.9mm] for the first string, and a "low" action would be 0.135" [3.4mm] and a "normal" action would be 0.150" [3.8mm] for the sixth string. In a similar set of online lessons, "Online Apprentice II, Make Your Own 1976 Miguel Rodriguez Junior Style Classical Guitar, c. 2008,[now also removed from the Web, he indicates that he uses 2.8mm action at the 12th fret for the first string and 3.6mm for the sixth string for this guitar project.]

8. In the book, "The Guitar Maker's Workshop", by Rik Middleton, c. 2004, ISBN1-86126-707-X, pp. 84-85, Middleton says, "The sixth string should have a clear space above fret twelve of 3-4mm for a student instrument and 4-5mm for a concert instrument. The first string should be 2.5-3mm and / or 3-3.5mm respectively."

9. In the book, "Classical Guitar Making", by John S. Bogdanovich, c. 2007, ISBN 978-1-4027-2060-4, p. 296, Bogdanovich says, "A typical string height for the sixth string over the twelfth fret is 0.140 to 0.145 inches [3.6mm to 3.7mm]. The height of the first string at the twelfth fret is typically 0.125 to 0.135 inches [3.2 to 3.4mm]."

10. In the book, "Making the Responsive Guitar", by Ervin Somogyi, c. 2009, ISBN 978-0-9823207-1-6, p. 150, Somogyi says, "The target action for flatpicked [steel string] guitars needs to be higher: 3/32" for the first string and 5/32" for the sixth, at the twelfth fret. ... The target action at the twelfth fret for the Spanish classical guitar is the same as for the steel string flatpicked guitar, or possibly 1 mm higher. [i.e. 2.4 - 3.4mm for the 1st string and 4.0 - 5.0mm for the 6th string].

11. In the book, "Contemporary Acoustic Guitar, Design and Build, Volume 2; Build", by Trevor Gore and Gerard Gilet, c.2011, ISBN 978-0-9871174-1-0, p. 21-11, the authors say, "For a classical guitar with a standard setup the action should be 4mm for the 6th string and 3mm for the 1st string."

12. From the classical guitar Web site DELCAMP.COM, (viewtopic.php?f=11&t=64845#topic4), "Luthier's" thread, topic "Frequently Asked Questions About Classical Guitars", by Luthier James Lister:
What is the correct action for a classical guitar?
Normally 3mm at the first string (top E) and 4mm at the sixth string (bottom E). These figures can vary up or down slightly depending on the player, but not normally by more than 0.5mm.
The action is measured at the 12th fret, from the top of the fret, to the bottom of the string.

To Summarize, here is a table of recommendations from these 12 luthier authors, for the action at the 12th fret for a classical guitar, in millimeters (mm):
First string Sixth string
Author Low Normal Hi Low Normal Hi
Wallo 3 4
Brown 4 4
Doubtfile 3 4
Cumpiano &
Natelson 3.2 4
Ramirez III 3 4.5 5.5
Courtnall 2.5 3 3.5 4
Schramm 2.5 2.9 3.4 3.8
Middleton 2.5 3 3.5 3 4 5
Bogdanovich 3.2 3.4 4 5
Somogyi 2.4 3.4 4 5
Gore & Gilet 3 4
Lister 3 4

The majority seems to recommend 3mm for the action on the first string and 4mm on the 6th string. The extremes are about a low of 2.5mm and a high of 3.4mm for the first string, and a low of 3mm and a high of 5mm for the sixth string. I general it is best to avoid the extremes unless specifically requested by the customer of a custom guitar.

Lance Litchfield

Re: Recommended action height at 12th fret survey

Post by Lance Litchfield » Fri Apr 11, 2014 12:31 am

can you confirm the measurements are all done the same way? Just want to check as I always fret the first fret when taking these measures. Cheers.

Robert England
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Re: Recommended action height at 12th fret survey

Post by Robert England » Fri Apr 11, 2014 1:01 am

Lance Litchfield wrote:can you confirm the measurements are all done the same way? Just want to check as I always fret the first fret when taking these measures. Cheers.
I have no idea how these 12 different people make their action measurements. They all seem to indicate that the correct measurement is between the top of the 12th fret and the bottom of the string, but whether they fret the string or leave it open I can't tell. But that shouldn't make a big difference at the 12th fret. (E.g. half of the displacement at the 1st fret, usually way less than 1mm, would be reflected in the 12th fret measurement.)

But how the measurement is made is a very interesting question. For the guitar at issue, I get 3 very different sets of measurements depending on what device I use for the measuring: Using a quality steel ruler propped on the 12 fret and sighting under the strings with a flashlight, I get about 2.9mm(1st)/3.9mm(6th). (This may be the way my customer is doing it.) Using an inexpensive electronic "Action Finder" I get 3.08mm(1st)/3.80mm(6th). Using the StewMac "String Action Gauge" I get 2.8mm(1st)/3.6mm(6th). The StewMac gauge is how I have been measuring action height at the 12th fret for a long time. This probably explains the difference in measurements between me and my customer, but I don't know which method to trust. Intuitively, the StewMac gauge seems the most reliable. I think I will make myself a custom set of "feeler gauges" with the appropriate thicknesses for measuring action height.

Robert

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Jae Lee
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Re: Recommended action height at 12th fret survey

Post by Jae Lee » Fri Apr 11, 2014 1:14 am

The customer who think 2.8 / 3.6mm action high must be a classical guitar beginner who used to play acoustic guitar. If my guitars have such a low action without buzzing, I couldn't be happier.

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Re: Recommended action height at 12th fret survey

Post by Imbler » Fri Apr 11, 2014 2:08 am

Doesn't mean it is right, but I use 2.5 at high E and 3.5 at low E. No buzzing, and easy to play. From what I read, action heights are lowering compared to the past. I don't know if it is due to tastes or to more precise setups today. I use a milled extrusion with sandpaper to level the frets as do many today. Did they in the past? I doubt it,
Mike

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James Lister
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Re: Recommended action height at 12th fret survey

Post by James Lister » Fri Apr 11, 2014 8:52 am

Thanks for doing the survey, Robert. Not too many surprises there, although Bogdanovich's 3.6/3.7 and 3.2/3.4 seems a bit off for a modern publication.

I should point out that the figures I gave in the FAQ post were more of a consensus based on what the luthiers on this forum have quoted, rather than my own figures. For my own guitar, I actually have the action set at 2.8mm/4.2mm, and for non-commissioned guitars, or where the customer just asks for a "standard" classical setup, I aim for slightly under 3mm treble, and slightly over 4mm bass.

Obviously the "best" action will be different depending on the player, the guitar, the tension of the strings, fret levelling and relief, so there are quite a few variables, but I think generally a difference between the bass and treble of at least 1mm is advisable. With a 1mm difference, you will always be able to get the bass strings buzzing more easily than the treble strings (all else being equal in terms of string tensions, fret levelling, relief etc.)

James
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Re: Recommended action height at 12th fret survey

Post by petermc61 » Fri Apr 11, 2014 10:23 am

James Lister wrote: With a 1mm difference, you will always be able to get the bass strings buzzing more easily than the treble strings (all else being equal in terms of string tensions, fret levelling, relief etc.)
Hi James

So why is this a design goal? Intuitively I would have thought all strings buzzing when pushed about equally hard would have been a more desirable objective.

Peter

Lance Litchfield

Re: Recommended action height at 12th fret survey

Post by Lance Litchfield » Fri Apr 11, 2014 10:48 am

Robert England wrote:
Lance Litchfield wrote:can you confirm the measurements are all done the same way? Just want to check as I always fret the first fret when taking these measures. Cheers.
I have no idea how these 12 different people make their action measurements. They all seem to indicate that the correct measurement is between the top of the 12th fret and the bottom of the string, but whether they fret the string or leave it open I can't tell. But that shouldn't make a big difference at the 12th fret. (E.g. half of the displacement at the 1st fret, usually way less than 1mm, would be reflected in the 12th fret measurement.)

But how the measurement is made is a very interesting question. For the guitar at issue, I get 3 very different sets of measurements depending on what device I use for the measuring: Using a quality steel ruler propped on the 12 fret and sighting under the strings with a flashlight, I get about 2.9mm(1st)/3.9mm(6th). (This may be the way my customer is doing it.) Using an inexpensive electronic "Action Finder" I get 3.08mm(1st)/3.80mm(6th). Using the StewMac "String Action Gauge" I get 2.8mm(1st)/3.6mm(6th). The StewMac gauge is how I have been measuring action height at the 12th fret for a long time. This probably explains the difference in measurements between me and my customer, but I don't know which method to trust. Intuitively, the StewMac gauge seems the most reliable. I think I will make myself a custom set of "feeler gauges" with the appropriate thicknesses for measuring action height.

Robert
Thanks Robert....the 0.5mm can be an issue when skirting with buzz tolerance I find however. For keeping things consistent and to check for any changes in action height with weather or damage etc, it's handy to know. Thanks for the collation of information.

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James Lister
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Re: Recommended action height at 12th fret survey

Post by James Lister » Fri Apr 11, 2014 2:51 pm

petermc61 wrote:
James Lister wrote: With a 1mm difference, you will always be able to get the bass strings buzzing more easily than the treble strings (all else being equal in terms of string tensions, fret levelling, relief etc.)
Hi James

So why is this a design goal? Intuitively I would have thought all strings buzzing when pushed about equally hard would have been a more desirable objective.

Peter
Good question. I would point out that as described above, I do aim for slightly more than a 1mm difference (typically about 1.2mm), but even then I think the basses will probably buzz first. My estimate would be that you'd need to go to above 4.5mm on the bass side to get a balance (buzz-wise) with a 2.8mm treble, and not many players are willing to cope with that high an action these days.

James
James Lister, luthier, Sheffield UK

Robert England
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Re: Recommended action height at 12th fret survey

Post by Robert England » Fri Apr 11, 2014 4:58 pm

I have double checked the figures in the Bogdanovich book.
Robert

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Brian McCombs
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Re: Recommended action height at 12th fret survey

Post by Brian McCombs » Fri Apr 11, 2014 6:06 pm

Great post Robert, very thorough. That info should be put into the FAQ.

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Re: Recommended action height at 12th fret survey

Post by Robert England » Fri Apr 11, 2014 6:42 pm

A follow-up; I purchased a Veritas Tapered Gauge, from Lee Valley, and re-measured the 12th fret action on the guitar I have been discussing. The results are 3.6mm for the 6th string and 2.8mm for the first string. These values are the same as those I got with the StewMac Action Height Gauge, and very different from the values obtained by the "ruler with squinty eyeballs" method. Interesting. How many people use the ruler-eyeball method and take the results as gospel?
Robert

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Re: Recommended action height at 12th fret survey

Post by simonm » Fri Apr 11, 2014 7:32 pm

Robert England wrote:... How many people use the ruler-eyeball method and take the results as gospel?
Robert
Moi for one. :lol:
Will have to invest in one of those gizmos.

Great idea. Thanks for doing the ground work. Some of the books are completely new to me - never even heard of them. Useful all round.

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Re: Recommended action height at 12th fret survey

Post by petermc61 » Fri Apr 11, 2014 9:10 pm

I measure the action heights accurately rather than eyeballing. The simplest and most accurate method is to start with two little bits of aluminium bar. Each bit of bar is 25mm wide and probably about 50-60mm long and I lay it under the string to be measured across several frets.

One bit of bar is 3mm thick which is used under the sixth string. The other is 2.5mm thick which I use under the first string. Both have been checked for thickness with a micrometer. I then use a set of feeler gauges to measure the gap and the bottom of the string and the top of the bar. An accuracy of say 0.05mm is easily achievable.

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Re: Recommended action height at 12th fret survey

Post by Steve Ganz » Sat Apr 12, 2014 5:31 pm

For an individual builder or repairer, it probably does not matter too much how the gap is measured, as long as it gives consistent results for that individual.
I use a calibrated wedge under the string. I can easily make one from headstock taper cut-offs in a few minutes. I regularly misplace them, but they all give consistent results for me.

3 and 4 mm is a good default. But I have players who want wildly different actions ...

Ramirez guitars are notable for the high action described.
Steve

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