My 1976 Guild F-212 XL is in need of a neck reset. The guitar is not damaged in any way. The action is simply too high for the guitar to be comfortable to play. I am going to remove the neck, alter the neck geometry, and set it back in place. Additionally, as the current bridge and saddle are too short to achieve optimal string height, I will replace them. Guild guitars have taken on legendary reputation for being difficult to disassemble. Let's see if this one lives up to its name. This article is dedicated to the countless Guild acoustic guitar owners whose guitars have desperately needed a neck reset.
A common practice to check to see if a neck reset is required is to rest a straightedge across the top of the frets of your fingerboard. As the test is presented, if the straightedge just kisses the top of the bridge, as opposed to ploughing down into the soundboard, you are to conclude that no neck reset is required.
Neck Reset Straightedge Test
If you happen to have a true straightedge (not a yardstick, not a ruler), and that straightedge happens to be thin enough to sit between the strings, and it happens to be of sufficient length to fit between the nut and the front of the bridge, and you can verify that one end of the straightedge is in contact with the first fret, and the straightedge is in contact with the fret at the body joint (12th, 13th, or 14th), and the end of the straightedge closest to the bridge is either touching the soundboard or is well below the top surface of the bridge, then YES, you can be fairly confident that your guitar needs a neck reset.
HOWEVER...
...this straightedge test does not tell you the whole story, a story I attempt to explain in detail in this article. It is quite possible that your guitar can pass the straightedge test (instead of falling below the top surface of the bridge, the straightedge is at the same height), but the guitar is in desperate need of a neck reset. This is the case with the guitar in the photo, above.
Most, if not all, of the guitar owning and playing world has some awareness of the common practice of lowering saddle height to adjust the string height above the frets for playability. The ubiquitous belief is that, as the action continues to get higher over the life of the guitar, you keep lowering the saddle until you can't get it any lower. At that point you either pay a small fortune to get the neck reset OR you try to unload the guitar. Along the way you simply live with less-than-optimal volume and tone, and probably aren't even aware of it.
The general consensus is that IF the guitar can pass the straightedge test AND you "have a little saddle remaining" THEN your guitar is fine.
Your guitar is NOT fine. What other factors inform me of this guitar's need for a neck reset?
Allow me to provide you with a much simpler, yet a much more definitive test to determine if a neck reset is necessary.
To produce both maximum volume and optimum tone, it is necessary to achieve maximum and optimum height of the strings off of the soundboard in front of the bridge. Why? Torque. On any given acoustic guitar, torque applied by the strings must be sufficient to rock the bridge, to set it in motion. Insufficient torque will result in weak output.
With the strings tuned to pitch, measure the height of the strings from the soundboard, directly in front of the bridge. This measurement should be no less than 1/2″ (12.7 to 14 mm). But for some rare exceptions, if you are getting a lower number measurement, it is safe to say that your neck geometry is off, and your guitar is NOT performing optimally. Of course, you will decide whether you wish to have it corrected, or not. Such a correction may be as simple as adding a taller saddle, and resetting the neck. But it may also require a new bridge.
Two additional factors should be considered to confirm (prove beyond a shadow of a doubt) that a neck reset is needed.
Before proceeding, I am going to assume that your fingerboard is relatively flat, and you are not dealing with any bow, twist, curve, cupping, etc., and your frets are relatively leveled, crowned, dressed, etc., such that you are not dealing with anything that would warrant intervention.
If your guitar is fitted with a Zero Fret, no additional measurements are necessary. Move on to Step 2b.
If the Nut on your guitar is acting as fret 0, as is the case with most acoustic guitars, and you are familiar enough with proper setups to know that your nut slots are cut and filed perfectly, and are as low as they can go without introducing string buzz, no measurements are necessary. Move on to Step 2b.
Nut slots should be cut and filed as low as they can go without introducing string buzz. The bottom of the nut slot should be the height of fret 0, had a fret wire been installed on your guitar instead of a Nut. You can verify this using a dial indicator made for the purpose, or you can use feeler gauges, or you can even sand a pencil in half, lengthwise, lay it on the frets and have the super-sharp pencil point mark the front edge of the nut. If your slots are sitiing above that mark, they can and should be lowered.
Very often, this little detail gets overlooked. In conjunction with Action height (Step 2b), Nut slot height is the primary distinction between a guitar that "plays like butter" and one that "cuts into my fingers." In additional to comfort, it plays a critical role in establishing the plane of the string path, which is why we are running down this rabbit trail to begin with. Verify the Nut slots are perfectly cut and filed and move on to Step 2b.
Establishing the string height for player comfort is the primary role of the neck geometry, not the saddle. You may want to read that last sentence again. The saddle, together with the bridge, stand the strings off the face of the soundboard at an optimal overall string height of 1/2″. Once that optimal height is established, leave it alone. Adjust your action at the neck joint.
The height of the string path from the Nut to the Saddle above the fret wire should be as low as it can go for your style of playing. If you are familiar enough with action height to know that your guitar is already set up with perfect action for you and your playing style, you do not need to go any farther; no more measurements are required. You can move on to the Conclusion.
If you are unsure about action height, measure the distance between the bottom of the strings and the top of the fret wire (NOT the fingerboard) at a point halfway between the nut and the saddle. It is typically safe to conduct your measurement at the 12th fret. You need only measure at the two outermost strings. That will include strings 1 and 4 for a Tenor guitar, or strings 1 and 6 for a 6 string guitar, etc. For a 12 string guitar, measure at string 1 and the larger diameter string of the 6th course (typically string 11). Generally acceptable heights are as follows (you may wish to be slightly lower or higher, depending on your playing style):
Overall string height measuring below 1/2″ may be corrected by installing a taller saddle, though a new bridge may also be required. If correcting the overall string height results in raising the action such that your guitar is now uncomfortable to play, your neck geometry is off.
If your overall string height is acceptable, BUT your action is too high, AND adjusting that action (such as by shortening saddle height, for example) would drop your overall string height below 1/2″, your neck geometry is off.
If your neck geometry is off, a neck reset is required to correct it. Your guitar is NOT performing optimally. You can read the balance of this article to gain some insight as to why that is. Whether or not you want to reset the neck or pay someone to reset the neck is immaterial to concluding when a neck reset is necessary to restore correct neck geometry.
My guitar, the one in the photo that inspired this article, the guitar that passed the straightedge test, has a bridge that is a mere 1/4″ tall. The saddle projects an additional 1/8″ to 5/32″ above it. Many would (wrongly) assume that "there is plenty of saddle left." Plenty of saddle to what with, exactly? Currently, when bridge and saddle height are added together, the overall string height only comes up to 13/32nds, not a minimum of the necessary 16/32nds (or 1.2″) for proper torque.
My guitar, the one in the photo that inspired this article, the guitar that passed the straightedge test, has a bridge that is a mere 1/4″ tall. The saddle projects an additional 1/8″ to 5/32″ above it. Many would (wrongly) assume that "there is plenty of saddle left." Plenty of saddle to do what with, exactly? Currently, when bridge and saddle height are added together, the overall string height only comes up to 3/8″ (13/32″ at best), not a minimum of the necessary 16/32″ (1/2″) for proper torque.
Compounding the problem, action at the 12th fret is a whopping 9/64″! If I were to shave the saddle down to try to get the action into a lower, more acceptable range, I would kill the sound of this guitar.
There is no question... I have but one choice before me, and that is to reset the neck of this guitar.
We'd like to assume that every guitar ever made had its neck set properly prior to being offered for sale. Unfortunately, that is not the case. More than one brand new guitar has needed a neck reset right off of the showroom floor to be optimized for performance. In such cases, a neck reset is necessary to correct a mistake, one made during initial construction. In most cases, however, a neck reset is needed to correct for glue failure and/or structural failure that has occurred later on in the guitar's life.
To better understand why I would ever need to deal with glue failure and/or structural failure in my acoustic guitar, let alone be faced with having to the remove the neck, adjust its geometry, and re-attach it, it really helps to learn more about how my guitar is constructed, and the forces that are working on and against it. It is also helpful to gain greater insight into what, exactly, goes into "optimizing a guitar for performance," generally referred to as a proper "setup."
Woods from various sources, dried to varying degrees of moisture content, assembled using a variety of adhesives, patterned after a variety of designs, and touched by one to some untold number of workers, man and machine included, become what we will affectionately refer to as "our (current) favorite guitar."
There are dozens of steps that must be taken to produce our current favorite guitar (roughly 30 to 80), depending on how you define a step. The end result can be measured qualitatively as the sum total of the steps, each building upon the previous step. It is a mistake to assume that a given design is already perfect and can never be improved upon. Whether you, I, or someone else is going to take on the task of correcting a given design is a separate discussion. Design considerations aside, believing that each and every step of construction is performed with accuracy, precision, love and care on each and every instrument ever made is more than a bit naïve. My point? Few guitars are perfect and things can and do go wrong. Often.
When tightened to pitch, steel guitar strings exert anywhere from 150+ lbs to 250+ lbs of pull between one end of the guitar and the other, seemingly seeking to fold the guitar in half. Considering the reality that most guitars are subjected to all kinds of temperature and humidity shifts, and depending on who built what, when and how, it is not unreasonable to expect something to change in a guitar over time. In fact, for the majority of instruments, it is unreasonable not to. When such change is sufficient, a neck reset is required to re-establish correct geometry.
If each and every component of a wooden acoustic guitar simply stayed put, precisely where it was placed when the guitar passed its initial Quality Control inspection, no guitar would ever require a neck reset. And there would be no need for truss rods. And saddles would never need to be lowered. And frets would never need replacing. But things don't always stay in place. Over time, and subjected to various environmental changes and wear, things move away from their original locations.
So what?, you may ask. So, what if everything isn't perfect, and things have moved a bit? What determines whether I need a neck reset, or not?
Playability is a highly subjective term, inspiring debates over such incendiary, highly subjective topics as:
Rather than step into the subjective morass of "How" your current favorite guitar sounds, we can (and should) focus on how to ensure it is sounding as loud as it can, and that it is being all it can be, all it was designed to be. That is something we can achieve.
The 1976 Guild F-212 XL that I am using as an example for this article sounds really good, just as you would hope for a jumbo Spruce topped, Mahogany back and sides, Guild 12 string. But it no longer comfortably playable. To attempt to do so, if I believed in such a thing, I would need to lower the saddle by 3/32″, essentially burying it in the slot. This would result in a more comfortable playing experience, but would negatively impact the volume and tone (which is already less than what it could be).
Left in a hot car, glues soften and guitars come apart. But you already know that, and that is not why I am bringing up automobiles in an article dedicated to a guitar neck reset. Beyond the obvious issue of heat damage, there are parallels that can be drawn between guitar and automobile ownership, and this may be helpful in gaining a different perspective regarding neck resets on acoustic guitars.
People ride in or drive automobiles that they rent, lease, or own for all sorts of reasons. For most of us a car (or truck or van) is a necessity as a means of transportation. For some, it is just a tool. For others, it is a status symbol or even a toy. Still others see it as a commodity to be bought and sold for profit. And there are those who would prefer to accumulate as many vehicles as possible, and perhaps one day charge admission to view them. Don't forget the professional drivers out there for whom an automobile is a showcase for their skill.
Regardless of the reasons for driving or owning a car, these vehicles are going to require servicing at some point. Some service items are relatively minor, while others are not. Keep a car long enough, or inherit it from someone else who kept it long enough, and certain things will have to be addressed. Consider the following (suggested) parallels:
| Automotive | Guitar |
|---|---|
| Washing | Cleaning |
| Waxing | Polishing |
| Garaging | Casing |
| Tune-ups | Setups |
| Tires | Frets and fretboard |
| Collision repair | Brace re-glues and split cleating |
| Reupholstery | Refinish |
| Transmission or Engine overhaul | Guitar neck reset |
You are welcome to map your own parallels. My purpose in doing so is the hope that you realize that whether you view the inevitability of maintenance and repair (such as a neck reset) to be a life-altering, traumatic encounter of ultimate devastation, and something to be avoided at any and all cost, or just another thing you need to take care of or deal with, is entirely your choice.
A neck reset is one of those things that, more than likely, is going to be required at some point.
To determine whether my guitar requires a neck reset right now, or not, I need to focus on an aspect of playability known as "action," the height of the strings above the frets. Action is an informative indicator regarding what is going on with my guitar.
Action - String Height Above Fretboard
Before attempting to address action and conduct a corresponding setup (which includes fret height, nut slot height, and saddle height), let alone prior to beginning any dramatic neck alterations (which can include originating metrics, target metrics, neck condition, neck joinery method, bridge height, soundboard condition, and even bracing), it is necessary to have a reference against which changes can be measured. An ideal reference is a flat fretboard (fingerboard). While it may not be possible, or even preferable (for reasons I will explain, next), to force the fingerboard into a perfectly flat surface, I need to be able to reference a flat plane across the surface of the fingerboard, before I can proceed. I say fingerboard, not neck, not even frets, as the surface of the board is my reference.
I have addressed the issue of having a deliberately wavy fingerboard versus a perfectly flat fingerboard in more detail in a section called The Hump, found in my article » Truss Rod Alternative. You may wish to pause and read this before proceeding.
A proper setup can be viewed as a remediation of the string height issue to improve playability. In addition to dialing in the correct nut slot depth, and/or raising or lowering the saddle height, it may also involve steps such as correcting neck bow and/or twist, flattening (planing) the fretboard and re-fretting with taller or shorter frets, correcting bellying, correcting bracing failure or collapse, installing the greatest strings in the world, etc.
Assuming I know what I'm doing, if my attempts to complete a proper setup on my guitar result in the strings either laying on the fretboard buzzing (action is much too low), or being so far away from the fretboard that they cannot be fretted (depressed to make contact with the metal frets) without significant effort and corresponding discomfort/pain (action is much too high), it is highly probable that my guitar requires a neck reset.
A wooden guitar neck is essentially a straight plane. I say essentially, as a given guitar neck may have just the slightest amount of forward bow in it, depending upon a player's preference for relief. Relief refers to a deliberate introduction or allowance of concavity along the surface of the fingerboard/fret plane in an attempt to mitigate string buzz, the result of the strings contacting the metal frets as they oscillate. Additionally, the fretboard extension, that part of the fretboard that extends beyond the point where the neck joins the body, may include fall-away. This is a slight, but deliberate sloping of the fretboard away from the path of the oscillating strings.
On a guitar having a perfectly flat neck, depending on the overall stiffness of the neck and the gauge of the strings, some forward bow will likely occur due to the pull of the strings. If additional bow is desired, more relief can be introduced by planing, carving or sanding material away from the fretboard, or by bending the entire neck forward using an internal mechanical device: the truss rod. When plucking or strumming the strings, a very light string attack requires little or no relief, whereas very aggressive string attack may require greater relief.
Check for Neck Bow
Many guitars, upon inspection, have necks that appear to suffer from excessive bow, often forward but sometimes backward. Excessive back (convex) bow will cause the strings to lay on the fretboard against the frets, making the guitar unplayable. On guitars whose necks have a single action truss or compression rod, it may be possible to simply loosen the tension on the rod and allow the strings to pull the neck forward enough to counteract the back bow. If the neck is equipped with a dual-action truss rod, it is usually possible to deliberately bow the neck forward. If the neck continues to curl backward, the condition of the neck will need to be addressed, first.
Excessive forward (concave) bow, a visible curling forward of the neck, will raise the action to a point where the guitar quickly becomes unplayable. Most modern guitar necks are equipped with a means of countering the pull of the strings on the neck, and an excessive forward bow may be able to be corrected by tightening the truss rod in the neck. If such corrections fail to make the guitar playable, a neck reset is probably in order.
Occasionally a neck will twist enough that one side or the other is raising the strings much higher than it should. Looking down the fretboard from one end of the guitar or the other and comparing the plane of the headstock/nut against the plane of the bridge/soundboard should help to confirm or alleviate any suspicion of twist. In some cases, the bridge has been planed or sanded into a wedge shape, either originally by design or during some re-design, intervention, repair, etc. If so, it is the plane of the soundboard alone, not the top of the bridge, that I must compare with the plane of the nut in order to determine if I am dealing with neck twist, or not.
Neck Twist Check - Nut
Neck Twist Check - Saddle
Severe twist may or may not be correctable. In lieu of straightening or replacing a twisted neck, sometimes cleverly messing with the geometry of the neck, body, bridge, and saddle is sufficient to keep a guitar playable without killing the sound. Sometimes the fingerboard can be replaced and planed to counter a twist. Sometimes.
Some necks are simply not straight to begin with; as in, they cannot even be forced into a flat condition. Such necks need to be addressed, separately, as a neck reset is not the proper solution. Before giving up on a troublesome neck, it is worth investigating whether it is the neck or the fretboard that is causing the problem. Sometimes a fretboard can be replaced more readily than an entire neck.
Removing the frets and flattening the fretboard lets me literally start from a level playing field. This is the right time to address the condition of the overall fretboard, such as its overall thickness, adjust the radius, increase or reduce fall-away, and determine the optimal fret height and fret material for the replacement frets.
If my action is really high, and I lower the height of my frets, the result is an even higher action. Sometimes, by installing taller frets and thereby reducing the distance between the tops of the frets and the bottoms of the strings, I can put off resetting the neck just a bit longer.
Once I know my neck/fretboard is straight, my next step in setting up proper action is to address the nut slots. This step pertains to fretboards whose nut acts as fret zero. The difference between a guitar that feels like a wire cheese slicer on my fingertips and a fretboard that "plays like butter" starts at the nut slots, specifically, in the distance between the top of the first fret and the bottom of the string as it rests in its respective slot in the nut. There should only be enough distance (the slots should only be close enough to the fretboard) to prevent the strings from resting on the first fret. A common test that can be conducted without using measuring tools (such as a dial indicator or feeler gauges) is to depress each string against the 3rd fret and "tap" each fretted string against the 1st fret. I am hoping to see only the slightest gap between the fretted string and the top of the 1st fret. Anything more than that is an opportunity to lower the nut slot.
Saddle height is not arbitrary, at least not if I am wanting my guitar to be all it can be. Reaching for the sandpaper to shorten the height of the saddle, in an effort to lower the action to make my guitar easier to play, is rarely the best solution if I am expecting maximum volume and optimum tone from my guitar. Assuming my neck/fretboard is flat, and assuming the strings are properly seated in nut slots that have been filed to the proper height (as low as they can go without buzzing), and assuming the saddle slot in the bridge is both cut to proper depth for that bridge and is perfectly flat across the bottom, the amount of saddle that extends above and beyond the top of the bridge should be determined by the necessary height of the strings off of the soundboard, not the fretboard.
To produce both maximum volume and optimum tone, it is necessary to achieve maximum and optimum height of the strings off of the soundboard in front of the bridge. Establishing the string height for player comfort is the primary role of the neck geometry, not the saddle.
To that end, you may see the benefits of having an easily adjustable neck, such as a bolt-on neck, where the neck joint can quickly be altered and shimmed. Action can be adjusted at the neck joint, leaving the saddle and bridge to perform at their respective peaks.
Break angle is a term that refers to the angle at which the string, emerging from the bridge (or tailpiece), "breaks" across the saddle as it continues its path to the nut. There is an additional break angle that can be identified as the string leaves the back of the nut in a trajectory to the post of the machine head (tuner), but that is a separate topic. Having sufficient break angle as the string leaves the back of the saddle is essential, but probably not for the reason you are accustomed to hearing.
On a brand new guitar having a pinned bridge, it is common to see the strings bend downward at the back of the saddle in a rather sharp angle. If we visit that same guitar 40 years later, it is common to see the strings emerge from the pin holes and lay flat across a saddle that is completely buried in its slot. Very often on guitars such as this, bridges get modified. Angled slots (ramps) are cut into the bridge at the front of the bridge pin holes, such that the string leaving the (nearly non-existent) saddle can once again bend downward behind the saddle.
A rather silly chase has ensued, arguing over an "optimal break angle to improve volume/tone", a chase that persists to this day. I fell for this one, not realizing that all I was achieving by ramping the pin slots on a dead sounding guitar was a (proper) anchoring of the string across the saddle. This was always most dramatically demonstrated when a saddle had been lowered (in an attempt to further delay a neck reset), and was almost level with the surface of the bridge, such that the string was no longer making optimal contact with the saddle, but able to bounce across the saddle as the strings were plucked. When you contrast the geometry of a string laying flat across the top surface of a bridge, barely coming into contact with the saddle, with that of a sharp downward angling of a string behind the saddle (achieved through whatever means), it should be apparent that the latter configuration will result in an improvement in volume/tone over the former.
Too sharp of an angle may result in frequently broken strings. If the saddle extends far enough out of the slot, an extremely sharp angle may physically break the saddle or, more commonly, may split out the front of the bridge.
What if, by ramping slots into the bridge pin holes, you can get that break angle seemingly just right, and your volume/tone has improved a bit, but you are now getting some buzzing as the strings are touching the front of the bridge, due to the saddle being buried in the slot? And, to add insult to injury, what if you still need to lower that saddle a bit more, as the action is not quite low enough? In even greater effort to hold off on that neck reset, you shave the bridge down to expose a little more saddle. The problem is solved, right? The buzzing is gone, the action is lowered, the neck reset is pushed out to a distant future date and you can live with the sound of the guitar. Congratulations. That may be all you need or want. But your guitar is NOT fine. It needs a neck reset.
It comes as quite the surprise to most players should they ever realize the actual mechanics of what is happening when the strings on their guitar are fretted or plucked. For the typical steel string acoustic guitar, a string is anchored at the bridge and is tightened at the machine head (tuner). Contrary to popular opinion, the steel string (operative word: "steel") is NOT stretching. Windings on the post of the machine head may be slipping or tightening, resulting in a loss of tension that requires re-tightening. But the steel string is NOT stretching. The ball end of the string may be re-adjusting its home position, even sliding up into the bridge pin hole, resulting in a loss of tension that requires re-tightening of the string. But the steel string is NOT stretching.
When fretted, it is wrongly assumed that the string is stretched as it is pushed or pulled away from its straight path as it makes contact with the fret wire. When strummed, the string will swing away from that straight path. We all know that the shortest distance between two points is a straight line, so there is a common assumption that the string must be stretching, or lengthening, in order to swing back and forth.
Imagine yourself holding the end of a large, long rope that you have tied to a tree. Stretch it taut and have a friend run and throw himself at the rope in an attempt to get you to break your grip. The rope doesn’t stretch. You move forward. As you then move back to your original position the rope is pulled straight again. Since your friend is hanging onto the rope, that momentum has them then pulling the rope in the opposite direction, which pulls you forward again. Naturally, you counter and pull the rope straight, and so on.
Since the string is not stretching or lengthening to accommodate this modified distance requirement, what is happening? When the string is plucked (pulled away from that straight line), it is the guitar that is making up for the change in distance. The guitar is moving to accommodate the string. Specifically, the bridge is taking on the primary role as it literally rocks forward and back as the string oscillates. This is occurring at extremely high speed, and the movement is very small. But it is really happening.
Torque is a description of rotational force or, better, torque is the rotational equivalent of linear force. Torque is the ability of a force to produce a rotation around an axis.
The bridge and saddle together form a single unit that both supports the strings at an optimal height and transmits the energy of the vibrating strings to the soundboard. Consider a tall violin bridge...
Violin Bridge
If the bridge on an acoustic guitar were fashioned to be tall enough to accomplish the task of supporting the strings at an optimal height without the addition of the saddle, the weight would be detrimental. There would be too great a “mass” for the strings to be able to move sufficiently. There would be a damping effect.
For that motion to occur, for the strings to oscillate, they must be able to be moved out of the straight line path formed from the nut to the saddle.
There must be sufficient torque at the intersection of string and saddle to maximize the string energy transferred via the bridge to the soundboard. Too much torque, applied by the addition of too heavy a gauge of string or by too great a height off the soundboard, risks ripping the bridge/soundboard/bridgeplate right out of the guitar! Too little torque, such as we find in guitars using too light a gauge of strings for their particular configuration of bracing/soundboard/bridge/saddle, and/or whose saddles are buried in their bridge slots, results in a weak output. For our purposes, using light or medium gauge strings, torque is determined by the height of the strings off the soundboard, as measured directly in front of the bridge.
In an acoustic guitar bridge, we see both dynamic and static torque at work. Dynamic torque references acceleration, or how quickly the bridge can be made to move. Imagine starting a bicycle race at the bottom of a hill, and the effort required to move bicycle from a resting position. In this camp we find the advocates for lightweight bridges (lighter, not shorter). The idea is to accelerate the bridge quickly into motion. Static torque refers to how an object in motion wants to stay in motion… On a level road it is downright therapeutic to pedal a bicycle once it is underway. In this camp we find the advocates for heavier bridges. We may only be talking about a matter of +/- 15 grams difference between the two camps, but it is enough difference to affect the sound.
After more than 150 years of acoustic guitar development, it has been determined that, for the typical steel string acoustic guitar, an optimal string height is at least 1/2″, or 12.7 to 14 mm. That string height is determined by the height of the bridge minus the depth of the slot plus the height of the saddle. Bridge heights of 5/16″ will require saddles that project above the bridge by 3/16″. Those same saddles would typically sit into the 5/16″ bridge by 1/2 the bridge height, or 5/32″. Extending the saddle any taller quickly moves into bridge split territory. This combination works well for extra light to light gauge strings. Lighter gauge strings mean lesser string tension at pitch, which means a lighter bridge can be set into motion much faster than a heavy one.
For light to medium gauge strings, a bridge height of 3/8″ (9.5 mm) with a saddle projecting above the bridge by another 1/8″ (3.25 to 3.5 mm) is very popular. That saddle will be setting in a slot cut 3/16″ into the bridge. Heavier gauge strings mean greater string tension at pitch, which means a little heavier bridge can still be accelerated quickly into a rocking state.
To reiterate: In order to experience maximum sonic output from a given acoustic guitar, the measured angle of the string breaking over the saddle is of much less importance than is the overall height of the string off of the soundboard. The torque applied from sufficient string height will actually rock the bridge forward and back in response to the force applied (energy transmitted) as the string oscillates. Break angle serves to lock the string down over the crest of the saddle, such that any shifting and rolling from side to side on the part of the string(s) is eliminated or minimized. Rather than being wasted, maximum energy can then be transmitted down into the bridge (and out across the soundboard).
On a guitar whose saddle has been lowered to the point where it is essentially buried in the saddle slot, the player may experience a terrifically weak output, where both volume and tone suffer markedly WHEN COMPARED to that same guitar where the neck geometry is corrected and the optimal saddle height/string height is restored. Adding a taller saddle may remedy the weak output, but without correcting the neck angle, the action height will then become untenable. This is an easy thing to prove: if you have a guitar with a nearly non-existent saddle, install a taller saddle, one that brings your string height to 1/2″ off of the soundboard (assuming this is possible without splitting out the front of your bridge. If not, you likely need a new bridge). String up the guitar and, realizing that the action is obviously now painfully high, have a listen. I believe you will hear something that is much closer to what your guitar should be sounding like. Of course, you will require a neck reset to be able to comfortably play this fine sounding instrument! The alternative is to re-install the low saddle and live with the weak output.
Shaving a bridge refers to planing, scraping, or sanding material off the top surface of an acoustic guitar bridge, typically while it is still attached to the guitar.
Why do such a thing?
If you are still with me at this point, I trust that you will have a better understanding regarding optimal overall string height. Unless a gross mistake was made during construction, and some monstrously tall bridge was installed, and planing the bridge will keep it in that 5/16 to 3/8″ height range, and the saddle height above the bridge will be in that 1/8 to 3/16″ range, such that total string height is NOT LESS than 1/2″, and string action is perfect for your style of playing... it is probably not in you or your guitar's best interest to further lower the bridge height.
The bridge of my guitar is an external brace, adding stiffness to the soundboard. In conjunction with the bridgeplate, the bridge is a fixture, providing me with a means of attaching the strings, as well as holding the saddle in place. The bridge is an acoustic coupler, transmitting the kinetic energy of the plucked and oscillating strings across the soundboard. Altering the mass of the bridge will alter the sound of the guitar, its volume and tone. I know people who would never tolerate anyone even suggesting to shave internal braces on their guitar (let alone actually reach inside the guitar and begin to remove wood), but would never think twice about shaving down the bridge.
As with the saddle, bridge size (height, width, weight, and density... or overall "mass") is not arbitrary. The bridge must be sized correctly to perform its tasks well. Too large or too small of a bridge will make for poor sound output. On center hole, X-braced guitars, the bridge is sized to rest atop the lower legs of the X. The mass of the bridge is relative to the responsiveness of the internal bracing and soundboard, as well as the tension of the strings. A heavier bridge may require a heavier gauge string to move it (a bridge "rocks" back and forth in response to the oscillation of the strings). A heavier gauge string will result in greater tension, and put greater demands on the bracing and the soundboard, which must be designed to support the extra load.
"But my guitar repair guy planed my bridge, made a new saddle, ramped the bridge pin holes, put on a new set of the world's greatest strings and now my guitar sounds better than it did before!"
I am sure it does. And it would sound even better, like it was originally designed to sound, had he FIRST established optimal string height, THEN reset the neck so that the action was perfect at that new target string height!
Bridge Lift
Bridge lift describes a visible gap between the soundboard and the back of the bridge. Such a gap may or may not require attention. Most guitar bodies have a finish applied prior to attaching the bridge. For a proper bond, the bridge needs to be glued to the raw wood surface of the soundboard, not the surface of the finish. To that end, the finish is either carefully removed or prevented from ever being applied in the area where the bridge will lay. It is quite common to leave a small border of finish around the periphery of the bridge, just enough for the bridge to rest on and provide for a clean visual intersection, as opposed to removing finish to the outside edge of the bridge, which would reveal an unsightly trace line all around the bridge. If (or as) the bridge rocks or tilts slightly forward, and depending on several other factors, including how wide that border of finish under the backside of the bridge is, a gap may or may not appear along the back edge, and that gap may or may not be stable for the life of the instrument.
Bridges should not require re-gluing. Fret wear is expected. Having a bridge come unglued should not be considered a common maintenance item.
A significant gap behind the bridge is an indication that something has gone wrong, either as a result of a slow process of failure due to poor materials or construction in the very beginning, or perhaps more sudden damage (like leaving a guitar in the hot car). The strings will likely be raised much higher off the fretboard than they should be. In the simplest of cases, where glue failure is due to insufficient glue and/or loose bracing, glue and clamping may be all that is needed to restore a guitar to playability. In some cases, such as an oily bridge that glue is refusing to bond well with, or too large of a finish border beneath the bridge, it may be better to completely remove the bridge in order to first address those issues. The above are best case scenarios. It may be that the soundboard is too thin or is in process of shearing due to severe grain run-out, or the bracing is simply insufficient to prevent the buckling that is contributing to the bridge lift. More dramatic steps may be necessary to mitigate a catastrophe.
It bears repeating that the thickness of an acoustic guitar bridge, also referred to as its height, is not (rather, should not be) an arbitrary measurement! Employing a production-minded technique certainly not unique to Guild, many guitar makers of yesteryear assembled their instruments by first attaching the necks to the body, and then selecting/making/modifying a bridge to fill the space between the soundboard and the plane of the fretboard (already established by the attached neck). With bridge height being the only criteria, it is easy to understand (years later) why the same model instrument could have such significantly audible distinctions from siblings produced on the same assembly line.
The bridge of an acoustic guitar is a multi-functional component. The bridge is (typically) responsible for pinning the strings in place. The bridge supports the saddle. The bridge, the only exterior brace on the soundboard, in conjunction with the bridgeplate, forms a unit that is responsible for transmitting kinetic energy generated by the plucked string(s) onto and across the soundboard, which is sandwiched between the two. It is crucial for the mass of a given bridge (taking into account the mass of the bridgeplate beneath it) to be sufficient to drive the top, to set the soundboard in motion. It is quite easy to rob the sonic life out of a guitar by adding or modifying a bridge that is improperly sized. Too small or too light a bridge will produce a very weak output. Likewise, too large/too heavy of a bridge can either act to dampen transmitted energy or completely overdrive the top.
Assuming the goal is to achieve the maximum sonic potential of a given soundboard, a crucial factor in determining the optimum size/mass of its bridge/bridgeplate is the overall stiffness of that soundboard after bracing. Overall soundboard stiffness will be determined by the material(s) used in the construction of the soundboard, as well as by the pattern, dimensions, and stiffness of the bracing.
The bridge must first be matched to the soundboard on which it will reside, and then the neck geometry can be determined. Not vice-versa.
If, in order to stave off the apparently inevitable neck reset and to keep the instrument playable, overall string height has been lowered by reducing the bridge’s height (by planing or "shaving"), it is quite possible that the bridge is now undersized. This typically translates into a quieter, lackluster sounding guitar. Efforts to improve the tone and/or volume, such as increasing the string gauge (moving from lights to mediums, or from mediums to heavy gauge), replacing plastic bridge pins with bone, or replacing bone bridge pins with brass or titanium, will be short-lived solutions. The fix is in - to restore such a guitar it will now be necessary to remove both the neck and the bridge, pair a new bridge (and possibly bridgeplate) with the soundboard, and reset the neck.
Bellying describes a condition where the lower bout section of the soundboard, the part directly behind the bridge, is pulled markedly upward by the tension of the strings. This is typically the result of the bridge rocking slightly forward, and can be due to several factors:
Bridge lift may accompany bellying, though not always. Is bellying ever acceptable? More than one luthier thinks so, with the maxim, "No belly, no tone" being echoed by both pros and novices, alike. If so, how much bellying is “too much?” Slight to modest bellying is simply the result of the pull of the strings on the bridge and the related structural integrity of a given guitar that resists the tendency of that string pull to fold the instrument in half. So long as everything stays in place, all is well and may remain so for the life of the instrument.
However, if the belly increases, it is quite possible that something is (or several "somethings" are) wrong. The string action will have been raised, as either the bridge is now tilting forward like a surfer catching a wave, or the entire soundboard is lifting. Resetting a neck on such an instrument may be a short-lived solution, as that belly may not be done lifting. Prior to assuming a neck reset is immediately necessary, it may be prudent to first address the belly bulge. Where bellying is the result of components having shifted away from their original positions, it is possible to "flatten" that belly using heat with a series of cauls. Sometimes bracing can be (or should be) re-glued and this is sufficient to deflate a bulging belly. Where bellying is the result of insufficient bracing and/or a soundboard does not have sufficient stiffness to stay flat, more drastic measures may be called for. Only after addressing bellying should you proceed with a neck reset.
In my experience, the primary culprit behind the need for Guild neck resets is the shifting of the neck block, the worst case scenario resulting in the shearing of the soundboard along the fingerboard extension on one or both sides. The soundboard does NOT have to split along the fingerboard extension for the neck block to have shifted, though it is probably only a matter of time...
You can read all about this topic in my article » Neck Block Shift and Soundboard Shear.
Thankfully, there is no evidence of splitting in this particular soundboard, yet, nor has the neck block provided me with any indication of failure.
Guild Dovetail Joint
Guild acoustic guitars, particularly older models, are somewhat legendary among repair shops, the consensus being that neck resets are more difficult to perform on a Guild than on other guitars. The Guild brand is among those who did not switch to bolt-on mortise and tenon necks, choosing to retain the more traditional glued-on compound dovetail joint. To reset a neck, it is first necessary to remove it. Guild necks were first attached to the body, and then the finish was applied. This complicates the removal process and adds the need for touch-up efforts once the neck is re-applied.
I stumbled across a great quote from Ireland's Gerry Hayes of Haze Guitars (https://hazeguitars.com), that perfectly expresses the common sentiment regarding the topic of Guild neck resets:
"Neck resets, therefore, range from relatively-easy (Taylor NT necks), to a-bit-more-hassle (bolt-on necked guitars) to break-out-the-steamer-and-the-tea (Martins), to break-out-the-steamer-and-the-whiskey (Gibsons), to oh-god-not-a-bloody-Guild (Guilds)."
The Finish - To remove the neck, the lacquer “seal” must first be broken. After the neck is reset, that lacquer must then be touched up. This can be complicated by a tinted finish, though it isn't a particular nightmare in and of itself. If, by extreme contrast, you have ever reset a Taylor neck (bolt-on, no lacquer touch-up necessary), you would understand the extra work involved on a Guild neck, along with the additional equipment and skills requirement.
The Glue - If you have reset enough Martin necks you may have run across that occasional instrument where it seems as though you could simply pull the neck off after exhaling a warm sigh across the heel. If you were to then encounter any one of the several Guild necks where any and all open space in the neck joint has been thoroughly flooded with glue, you would likely conclude that Guild neck resets can be more difficult to remove.
Some Guild necks are more difficult to remove than others, although few, if any of the ones I have encountered from the 1970s and up through 2010 have ever been as easy to remove as the bulk of Martin necks I have removed from the same period. Unfortunately, I cannot provide anyone with an authoritative list of which Guild guitars are more difficult than others, as it remains a mystery even to me until after I have started on a removal.
At issue is the amount of glue applied in the neck joint, and the surfaces to which the glue has been applied. All that should be required of a properly fitted compound dovetail joint is a brush (or fingertip) stroke of glue along the two sides of the tail. The purpose of the adhesive is merely to prevent the tenon from sliding upward in the mortise, the reverse direction from which it was “set.” The one and only possible reason I can think of for applying copious amounts of glue to a dovetail joint, other than ignorance (not knowing any better), is to compensate for a sloppy fit. So, rather than take the time necessary to correct the actual problem, the loose fit, someone just adds more glue to hold the neck in place.
You may have heard someone speaking about neck angle and/or neck geometry and wondered what they were referring to. In addition to the shape, width, thickness, and overall weight of a given acoustic guitar neck, the angle of incidence at which that neck joins the guitar body is a critical factor in both realizing the sonic potential of the guitar and determining its playability.
On an aircraft, such as the high-wing Cessna in the drawing below, the Angle of Incidence between the chord of the wing (imagine a straight line drawn through the center of the leading and trailing edges, shown by the red line) and the longitudinal axis of the body (shown by the green line) can be clearly seen.
Cessna wing Angle of Incidence
When applied to the guitar, there are two angles of incidence that can be considered. The first is the plane (as in planar, not aircraft) of the neck and/or neck/headstock in relation to the plane of the body. The second is the string path in relation to the body and neck.
Consider the side profile of a Fender Stratocaster. The longitudinal axis of the body is shown by the green line. The red line shows the string path. Notice how the neck, body, and headstock are all in parallel with the longitudinal axis of the body. The "chord" formed by the string path in relation to the longitudinal axis of the neck/body unit demonstrates a very shallow angle of incidence.
Fender Stratocaster
Contrast the Fender Stratocaster with the Gibson Les Paul. Again, the longitudinal axis of the body is shown in by the green line, and the red line follows the string path. Note how the neck deviates from the longitudinal axis of the body, and the headstock deviates from the longitudinal axis of the neck. Compared with the Strat, the "chord" formed by the string path in relation to the longitudinal axis of the neck/body unit demonstrates a sharper angle of incidence.
Gibson Les Paul
As you can see, the angle of incidence of the typical acoustic guitar neck, as well as the angle of incidence of the typical acoustic guitar string path sits comfortably in between the Les Paul and the Strat. The angle of incidence of both the neck and the string path of an acoustic favors that of the Strat, where the angle of incidence of the headstock of an acoustic is more akin to that of the Les Paul.
Acoustic Guitar
The angle at which the neck joins the body is not arbitrary; it is intrinsic to the design of that guitar. Failing to target the optimal neck angle, an under-set or over-set neck will negatively affect playability, at the very least, and actually affect the overall tonal quality of the instrument.
What, exactly needs to be corrected in order to improve playability?
The most common approach to resetting the neck, and that endorsed by guitar techs and repair shops throughout the Earth, is to entirely ignore Overall string height, instead using the height of the existing bridge as the reference against which measurements will be taken and calculations will be made. Among the instruments on which this approach is taken, most will require a negative reset. This means that material will need to be removed from the heel in order to drop the headstock and raise the plane of the tops of the frets above the soundboard. There is such a thing as a positive reset, where material must be added to the heel to prevent the strings from laying on the frets, but that is atypical.
A straightedge is laid across the tops of the frets. An assumption is made that the top surface of the (existing) bridge should be on the same plane of the tops of the frets. When the plane of the tops of the frets falls below the surface of the bridge, the measured difference between the two is multiplied by the length of the neck heel, and the resulting product is then divided by 1/2 the scale length. This determines the maximum amount of material that will be removed from the heel cap, that number being gradually reduced to 0.00 where the heel meets the bottom of the fingerboard. A "wedge" will have been removed (shaved, planed, chiseled, sanded) from the heel that lets the neck tilt farther back and away from where it was before beginning the neck reset.
Basic Neck Reset Calculation
When I am resetting a neck, to determine how to address the neck heel I ignore the existing bridge and make my calculations against my target overall string height. If I can achieve that height using the existing bridge (and typically fashioning a new, taller saddle), great. If not, I make a new bridge.
While this approach is not dissimilar to setting a neck on a brand new guitar, there are additional factors to consider when resetting a neck on an already built guitar, factors that will affect the measurements used to determine how much material to remove from the neck heel. These factors include bellying behind the bridge, sinking in front of the bridge, and shift/collapse at the neck block. It is advisable to take measurements with the guitar strung to pitch and compare those results with measurements taken after the strings are removed. For the soundboard measurements, you can use a dial indicator that references the rims. You can also lay a straightedge across the top and note the deviation from a flat plane.
Soundboard Dial Indicator
More coming, soon...
Bolt-on or glue-on? How to apply heat.
Break the seal. Bolt-on or glue-on? Steam? Heat Stick?
Mortise and Tenon, Dovetails and compound angles
Materials, Optimal size
Proper fitting, glue choices
Touch-up, drop fill