Follow along and learn how to set-up your guitar from start to finish beginning with: Adjusting The String Height, followed by: Adjusting The Truss Rod, and finishing up with: Setting The Intonation.
Your strings should be in good condition and the neck free of defects which might limit adjustments of the action such as neck warp or excessively worn and uneven fretwork.
Adjusting String Height
String height is an easy adjustments to make. Measure the height of the string over the highest pair of frets and adjust the saddle up or down as needed. Slacken the strings before making string height adjustments, this will save on wear and tear on adjustment screws and make turning them easier.
Bridges with individual string saddles typically use small hex wrenches. Fixed bridges are adjustable on the treble and bass sides of the bridge by screws or thumb wheels.
Personal preference comes into play as well as the quality of the fret work in determining how low or high to set the string height. The illustration above shows a measurement of 1/16″ (2mm) which is a medium action.
String Height and Playing Style
When considering how high to set the strings, consider the playing style in addition to the type of instrument.
- Traditional acoustic instruments, and playing styles that favor strumming, open chords and a desire for clean, loud notes work well with a medium-high string height, 2 – 3mm or more, as suites the player.
- Vintage style electrics, and those going for a combination of comfortable chording and soloing with room to “dig-in” and play heavier styles do well with a medium string height, 1.5 – 2mm.
- Players preferring a very light action and for those wanting to “shred” may favor a low action, 1 – 1.5mm.
The player and their instrument play a large part in determining a string height that is comfortable and accommodating for the player’s chosen style.
String Height Adjustment Tips: Make sure your tools are the correct size. Screwdriver tips should match screw heads to avoid slipping. Hex wrench or Allen key tools should be the correct size to avoid stripping small adjustment screws. Consult the manufacturer of your instrument if you are not sure what size tool you need. Sizes vary between imported and domestic instruments.
A guide to reading a ruler.
Part Two: Truss-Rod Adjustment
It’s important to understand the role the truss-rod plays in affecting the action. The the primary function is counteracting string pull to relieve or add bow to the neck under string tension. The ‘action’ (all the parts that anchor the strings, divide their length, and apply tension to them) work together in a balancing act that, when carefully adjusted, keep the instrument playing optimally.
Truss-Rod Lore: The function of the truss-rod has been the subject of some debate. Basic physics dictate that “a string of a given diameter and material at pitch is always at the same tension”. Some would suggest that the when the truss rod is adjusted to counteract the strings pull, which finely controls the amount of relief at the middle of the strings length, this adjustment has no other effect on playability or tone.
Another school of thought, which we at ModGuitar subscribe to, suggests that wood and strings and the other parts of the instrument being imperfect leave room for fine tuning, and while under tension are reactive. Such that subtle adjustments can make a neck feel springy or stiff, thereby affecting the ‘feel’ of the instrument.
It will be your quest to experiment (carefully!) and come to your own conclusions. Please be very careful when making truss-rod adjustments, particularly on older more fragile instruments. It’s very easy to accidentally strip the adjustment parts or your tools, and at the worst, snap off the end of a truss rod which can leave the instrument unplayable.
Measuring Relief
Before making truss-rod adjustments first measure the string relief. Relief is the amount of space between the bottom of the string and the top of the fret.
Relief is the bow in the middle of the neck under tension set to compensate for the nature of a strings vibration which expands in the middle of it’s length in an elliptical pattern when plucked. This is easily observed by simply plucking a string and looking closely at it with a strong light behind it.
Tools required for Measuring neck relief, and Truss-Rod adjustment
A capo to hold down the string at the first fret.
Feeler Gauge Set – the gauge of .010″ is a good starting point for a medium action.
Truss Rod Adjustment Tool (usually a hex or Allen key for Fender’s, and a small adjustment wrench for Gibson’s)
Truss Rod adjustment, beginning with measuring neck relief
The Procedure For Measuring Relief.
With the guitar fully stung up and tuned to pitch.
- Put the capo on at the first fret. Use the feeler gauge leaf that says .012″/.305mm (this is a medium amount of relief for an electric guitar strung with 10s). With one hand, press the string down at the highest fret – being careful not to push down too hard which can make the string deflect upward.
- Slide a feeler gauge over the 7th fret and under the string. This is a little tricky, and requires a steady hand. The idea is to just barely brush the bottom of the string while sliding the gauge as evenly as possible over the top of the fret. Practice will give you a ‘feeling’ for it.
- If there is no contact between the feeler gauge and the string, or the relief is lower move up or down in the feeler gauge range until you’ve pinpointed how much relief is present. There are fancier ways of measuring and adjusting relief, but this one is simple and as accurate as you need.
- Once you’ve established how much relief your instrument has, you can then adjust the truss-rod to dial in the amount that correct amount. Make all truss rod adjustments with well fitting tools and in small increments (1/4 turns). If you find that you have forward bow (no relief) or back bow (to much of relief) your neck may be warped or the truss rod already broken.
- A feeler gauge of .012″/.305mm represents a medium amount of relief. Speed players, preferring a light and low action might prefer .008″/.203mm, or even a flat neck. Players using heavier strings, acoustic guitars, to facilitate a strumming style of playing might want .014″/.356mm to.016″/.406mm.
- You may need to make small adjustments, let the instrument rest, then make further fine adjustments.
Most set-neck guitars use a threaded nut for truss-rod adjustment which is located under a plastic cover at the head stock end of the guitar. Bolt on necks usually have a hex nut that is adjusted thru a small opening at the head-stock or neck heel (heel end adjustments may require removal of the neck for adjustment). Make sure you have the correct size tool for the job.
Some Luthiers prefer to slacken the strings to make truss-rod adjustments, particularly on vintage instruments. Unless you need to make major adjustments, you can carefully adjust the truss rod under full tension for most newer guitars.
Making Truss Rod Adjustments
- The truss-rod for most instruments tightens (flattens the neck against string tension) by turning clock-wise. Bow is created by loosening the truss-rod counter-clockwise.
- Hold the neck firmly or on a workbench. You can also set the guitar standing up on the floor, held steady with your legs. Carefully turn the rod a 1/4 turn at a time. The motion should be firm and fluid – You may feel some resistance if the parts have settled over time. If you find it hard to turn, or it seems to offer a lot of resistance, or does not seem to effect the amount of relief -STOP-, there may be something wrong with the truss rod. Never force the truss rod, it should turn easily. if the truss rod is not easily turned or adjustments seem to have no effect the instrument will need to be taken to a luthier for repair.
- Make small adjustments, pausing to let the insturment rest, check the tuning, and take measurement of the relief.
You’ll find that as you adjust the truss-rod the relief changes in a measurable manner. You will be able to set it to your exact amount using the feeler gauges. Sometimes a guitar won’t seem to have enough range of adjustment or one of the other problems outlined above. That’s when it’s time to take it in and let a pro see what they can do for you.
Truss Rod Tips And Conclusions:
It’s a good idea to recheck your truss-rod adjustments after a day or two. Don’t be tempted to spray WD40, or other lubricants or oils into or around the truss rod. These chemicals can weaken the wood and/or degrade the finish and glue seams holding the neck together. If the truss rod nut is removable, a tiny amount of lithium grease or Vaseline can be applied to the thread of the nut.
Seasonal weather changes may require minor adjustment Spring and Fall for optimum playability.
Truss rod adjustment is easy to do yourself, but it does take some awareness and a careful hand. Like many guitar repair and modification tasks, experience is the best teacher. If you’re leery about making these adjustments, take it to a pro and ask them to show you how they make the adjustment.
Setting the Intonation
Intonation is adjustment of the string length at the bridge for different string gauges so that the notes played are as “in tune” as possible. With the string height set, and the relief set (truss-rod adjustment), the instrument is ready for Intonation adjustments. It’s important to set the intonation last because the string height and truss-rod adjustments both, minutely, effect the string length and thus the intonation.
Intonation De mystified
The guitar is an imperfect instrument. The mathematical calculations that define where the frets are placed is perfect on paper, but on the actual guitar other factors come into play.
Different string gauges are needed, along with intonation adjustments, to have the strings play relatively in tune with each other. The guitar is never really in perfect tune, rather it is balanced to sound as good as possible for chords and playing with other instruments.
Buzz Feiten has developed a method to compensate the strings length to provide a hybrid intonation setting. Other companies have developed compensated nuts, and even spanned fretting systems with the intention of solving the intonation problem. This article focuses on setting the intonation on a standard guitar that does not have any special enhancements.
Measuring and Setting The Intonation
For this tutorial we are using a standard sets of strings (either nine or ten gauge) tuned to EADGBE standard. The image below is a good starting point for setting your intonation – but there is a little secret trick that we have found that makes it work better.
Notice the stair-step pattern the saddles are in. The Fender style bridge (on the left) has more adjustment travel forward and back than the Gibson bridge’s saddles (on the right). The Gibson style bridge is installed at a slight angle (indicated by the arrows).
The ModGuitar Intonation Trick
To get a head-start on getting the intonation set, and to double check the intonation as it is currently set, use a ruler to precisely measure the length of string between the center of the 12th fret and the point where the string passes over the bridge saddle.
The 4th string tends to be the most balanced between gauge and tension, which results in the bridge saddle being intonated at exactly half the scale length.
For other scale lengths divide the total scale length by 2 and use this as your anchor point of the 4th string bridge saddle.
Check this measurement on the instrument, manufacturers occasionally alter the exact placement of frets and use slight variations on standard scale lengths. What we are measuring is the exact middle point of our scale length.
Intonation Trick, step-by-step
- First, using a precision ruler, measure and set the bridge saddle for the 4th (D) string. This will be our anchor point for positioning the other saddles.
- For 25.5″ scale length guitars set the 4th string bridge saddle at 12.75″/32.35cm.
- For 24.75″ scale length guitars set the 4th string bridge saddle at 12.375″/31.45cm.
- Once the 4th string bridge position is set, match the placement of the rest of the saddles to the above illustration. Each saddle will be offset roughly 1/16th of an inch, with the third unwound G string set back further.
This is a quick trick to get the bridge saddles close to the correct intonated position. Fine tuning will still be advisable for the best sound.
Fine Tuning Intonation Using An Electronic Tuner.
Fine tuning the intonation is done by comparing the twelfth fret note, with the open string note. We use the twelfth fret harmonic as a tuning reference because the harmonic is unaffected by fretting, and is the pitch of exactly the mid point of the guitar’s scale length.
- The open note and the twelfth fret harmonic are relative to each other. The twelfth fret harmonic is an octave above the open string pitch.
- The fretted notes are compensated by adjusting the bridge saddle so that the fretted notes match as closely as possible the open string pitch (or the 12th fret harmonic).
- Finger pressure, variance in scale length, fret size, and string gauge effect intonation.
Now that we’ve explained a little of the theory behind the method let’s take a look at how fine intonation adjustments are made.
If you’ve used our Intonation trick above, now you are ready for fine tuning the intonation.
For Fine Tuning Intonation:
- Play the 12th fret harmonic, adjust the tuning until this pitch reads true.
- Play the note at the 12th fret. Observe the tuning. Is the string exactly in tune, sharp, or flat?
- Adjust the string saddle to compensate for the difference between the 12th fret harmonic note, and the open string note in small increments.
- Re-tune the string using the 12th fret harmonic – then compare again to the note at the 12th fret, continue adjustments until the pith matches.
- This technique is then repeated for all the strings to complete the intonation fine tuning. Note that the saddles should not require more than 1/8″ or so forward or backward travel to fine tune the string from the ‘land marked’ measured position. Strings that are dented, grimy, or just very old may not play true and be very hard to make accurate intonation adjustments.
When setting the intonation on electric guitars using the bridge pick-up position tends to work better with electronic tuners.
If the string played at the 12th fret is observed to be flat compared to the 12th fret harmonic then we know that the string length is too long, and the string saddle needs to be adjusted forward.
If the 12th fret note is shown to be sharp relative to the 12th fret harmonic, that indicates that the string’s actual length is too short, so the string saddle is adjusted back.
The above illustration shows the 12th fret harmonic matching the 12 fret pitch. This string is correctly intonated.
Common Intonation Problems and Solutions
Question: A string can’t seem to get set correctly no matter how far I turn the intonation screws. It just won’t go sharp or flat the way it needs to. What is wrong? Answer: You can set the intonation so far off that it cannot be adjusted properly, though it will seem to be close. This is because the range of adjustment of the bridge saddles is very fine. A common problem is to have the saddle set too far forward or back to begin with. Solution: Use our ‘land marking’ trick (as described in this article) to get your saddles back within the proper range relative to your guitar’s scale length – then fine tune.
Question: Changing string gauge (from 9s to 10s, etc), do I need to adjust intonation?
Answer: A change of string gauge up or down one gauge may require fine intonation adjustment. A good rule of thumb is that the heavier the gauge of string the more the bridge saddle will need to be adjusted back.
Setting up the guitar is a process in several steps, each of them necessary to create a balanced state for optimal playability. By following the methods described in this article, you can effectively adjust and maintain the playability of guitars and bass instruments. With practice, these adjustments will become second nature, and are valuable skills in assessing new and used instruments for purchase or sale, as well as keeping your own instruments ready to play at their best.