This page starts with how to intonate an electric guitar;
even if you have an acoustic guitar, its worth reading this page first, as it will give you a good insight on intonation.
What is intonation
when an instrument is properly intonated, all the open strings and every note on the fretboard should sound at their correct pitch. If you've tuned the open strings and then one octave higher at the 12th fret, the intonation should be perfect and the instrument is in tune with itself.
Now try the intonation on all the strings on every fret. You will find the intonation sharp on the B G A D E strings, this effect is often slight rather than dramatic, but even slight intonation imbalances are noticeable enough to be annoying and demand adjustment
Why is your guitars intonation not correct
your guitar may be out of tune due to many things: your finger pressure over-bending the string, the frets being too high or inaccurately on the fret board, inaccuracies in the strings themselves, but is mainly due to the height of the string above the fret, The top E and B will be slight with the degree of inaccuracy increasing as you go across the G D A E strings.
To have perfect intonation, is the Holy Grail of the guitar maker, and is something most of us will never achieve, but we can get close, so from now i use the word near, so for near perfect intonation on all the strings on all the frets read the instructions below.
My advice is
before making any adjustments check the neck relief, see photo on the right. This is vital as it affects all further adjustments.
Using a metal ruler or straight edge, lay it over the frets from the 1st to the 12th fret and using a set of feeler gauges adjust the truss rod until you get less than 2 to 4 thousands of an inch clearance at the 7th fret, see picture
Intonating a guitar or bass can be a meticulous and time-consuming maintenance procedure, but the basic principles behind it are actually pretty simple.
When an instrument is properly intonated, all the open strings and every note on the fretboard sound at their correct pitches. If your guitar still sounds noticeably out of tune even after you’ve tuned the open strings, the intonation is off - that is, the instrument is out of tune with itself.
This effect is often slight rather than dramatic, but even slight intonation imbalances are noticeable enough to be annoying and demand adjustment.
Wonky intonation isn’t uncommon at all. Guitars are machines after all, and machines require maintenance. Your guitar is subject to environmental conditions and occurrences that more or less continually mess with its intonation, especially climate. Even under normal circumstances, periodic intonation is usually necessary, and it is in fact one of the main elements of a setup, which is perhaps the single best maintenance procedure you can have performed on your instrument.
Constant fluctuations in intonation are exactly why most guitars are designed with adjustable intonation mechanisms. Intonating a guitar puts it in tune with itself by slightly shortening or lengthening each string, which is done using the adjustable string-length mechanisms found at the bridge. The bridge saddles over which each string passes can usually be moved forward and backward; that is, closer to and farther from the nut (the saddles can also be moved up and down in order to adjust string height, or action).
If, using an accurate tuner, the string is found to be in tune both when fretting it at the 12th fret and when sounding its 12th-fret harmonic, the string is correctly intonated and you’re in good shape. The string is in tune “with itself.”
If, however, there’s a tuning discrepancy between the fretted 12th-fret note and the 12th-fret harmonic, the string is not correctly intonated and requires adjustment. In that case, the fretted 12th-fret note will sound either sharp or flat compared to the 12th-fret harmonic, and this is where two basic principles come into play.
First, if the tuner indicates that the fretted 12th-fret note is sharper than the 12th-fret harmonic, the string must be slightly lengthened until both pitches read as in tune. That is, the bridge saddle must be moved farther from the nut until both pitches are correct.
Second, if the fretted 12th-fret note is flatter than the 12th-fret harmonic, the string must be slightly shortened until both pitches ring in tune. That is, the bridge saddle must be moved toward the nut until both tunings read correctly. Actually, slightly raising the saddle will sometimes adequately shorten string length.
Although there are many different bridge designs for electric guitars and basses, most if not all include some provision for adjusting intonation relatively easily by using moveable bridge saddles. These are most often adjusted using a small screwdriver.
How to setup the intonation on a electric guitar
the Fender way
The new zero fret and nut
Why has it not been done before
Instead of having a guitar nut that requires nut files to adjust the string height. Fit a guitartec modified nut that takes a fret the same height as yours. All you need to do now is adjust the saddles until you get the action you want, job done
I have developed a new compensated nut for a Fender Telecaster:
this cures the age old intonation problems
Below a Telecaster bridge showing how the saddles now sit with a new guitartec compensated nut fitted.