Post by CTGull on May 19, 2017 6:21:15 GMT -5
The purpose of this guide is to remove the mystery of the guitar setup; what it is, what & how to check, and how to adjust it. Some steps are fairly simple, some require proper tools, and some can damage your guitar if done improperly. Proceed with caution, ask questions or get professional help if you are unsure what to do.
A guitar setup is adjusting the guitar to play and sound its best. Since an acoustic guitar is made of wood, variances in temperature and humidity and years of string tension can affect the setup, as can changing to lighter or heavier string gages.
Parts of the guitar: body, bridge, bridge pins, strings, fretboard, headstock, tuners. Part of the guitar that are affected with a setup: neck, truss rod, saddle, nut.
A basic setup consists of adjusting the neck relief, action and nut height.
WHAT IT IS:
The neck relief is the curvature of the neck that allows you to press the string at a fret and the string won’t buzz at the next fret. Excessive neck relief will result in high action, but the neck relief is not the only cause of high action.
The action is the distance between the strings and the 12th fret. High action makes the guitar very hard to play and will pull the strings out of tune when they are fretted.
The nut height (also known as nut action) affects how easily chords can be played in the first few frets. It will affect the string action to a small degree.
WHAT & HOW TO CHECK:
The neck relief is checked by holding the string down at the first and 14th frets (last fret before the body). Holding down the first fret takes the nut out of the equation. There should be a very slight gap at the 7th fret, .005” to .008”, about the thickness of 2 pieces of paper. Checking the low E and high E should be sufficient.
The action is measured at the 12th fret with the string held down at the first fret; again it takes the nut out of the equation. I like to see between 5/64” and 3/32” for the low E. Over 1/8” makes the guitar very hard to play. The high E string action should be 1/64” lower than the low E string, so I like to see 1/16” to 5/64”. The action for the other strings should taper from the height of the low E down to the high E.
Assuming the neck relief has been properly set, the cause of high action is typically a bad neck angle; the neck is pulled upward by string tension over time. The neck angle can be checked by laying a straight edge (I use a 25” one) on the fretboard. The end of the straight edge should be at the top of the bridge or slightly above it. If the straight edge ends below the bridge the neck angle is bad. It’s possible the neck is bowed (not related to neck relief) and the straight edge will only contact the neck at the first & last frets, throwing off the neck projection measurement. Typically that’s a guitar badly needing a neck reset.
The nut height is checked by pressing the string at the 3rd fret. There should be a very small gap at the 1st fret, checked by pressing directly on the first fret and feeling just a little movement, it should be very hard to see but you should feel and hear the string hit the fret. All strings need to be checked.
HOW TO ADJUST IT:
If the neck relief is too great (typical in guitars that haven’t been adjusted in a long time), it is adjusted by turning the nut on the truss rod. The truss rod nut is either in the head stock (covered by a plate) or inside the guitar. Typically a 4mm or 5mm Allen wrench is required. Many times the truss rod will be loose and need to be turned until resistance is felt, then checked again. The guitar must be tuned to pitch before and during a truss rod adjustment, the tension of the strings will affect the curvature of the neck. Turning clockwise will decrease the necks curvature, counterclockwise will increase it. Once some resistance is felt while adjusting, turn 1/4" of a turn, tune the guitar to pitch and check the neck relief again. If the truss rod nut won’t turn or takes an extreme amount of pressure, see a professional, over torqueing it could damage the truss rod or the neck.
The action is adjusted by changing the height of the saddle, either sanding the bottom or adding material. The neck relief must be properly set first. The amount of material to be added or removed from the saddle is double of the required change at the 12th fret, the 12th fret is halfway between the nut and the saddle. There is typically 1/8” (or less) of saddle sticking out of the bridge so the maximum adjustment would be 1/16” at the 12th fret. But you have to leave some of the saddle above the bridge so the adjustment would be less than 1/16”. Lowering the height of the saddle changes the angle between the bridge pins and the saddle, which is called the break angle. The break angle provides the force of the strings pressing on the saddle; a very shallow break angle will reduce the transmission of sound from the strings to the guitar top. The bottom of the saddle must be square to the sides otherwise the contact surface touching the bottom of the slot in the bridge is greatly reduced, reducing the efficiency of sound transmission from the strings.
Typically as a guitar gets older the tension of the strings causes the neck to bend upward (different than the curvature of the neck relief) and sometimes will cause the end of the fretboard to push into the top of the guitar. Adjusting the height of the saddle can help this, but eventually the neck angle becomes too great and a neck reset is required. A neck reset removes a triangle of material from the heel of the neck (where it contacts the guitar body) to bring it back into proper alignment. Most guitars have glued on necks, making this very difficult and expensive.
Something else that affects the action is the angle of the bridge and the area of the top behind the bridge. Over time the tension of the strings can also cause the back of the bridge to lift, typically taking the top with it. This can also cause a bulge in the top behind the bridge called a belly. If the back of the bridge is lifted, that will increase the action. There are other internal problems that can cause this also, such as a loose brace. There are ways to flatten the bridge and top but that is beyond the scope of this guide. The bridge can also come unglued from the top, resulting in a gap under the bridge. In this case, the bridge will have to be removed and properly reglued, injecting glue into the gap will not fix it.
Adjusting the nut height (or nut action) requires special files to deepen the slots. If all the slots are too high you can remove the nut (typically held in with a little glue) and sand the bottom slightly. This sounds simple but a cheap nut could break when tapped to remove it, or the guitar finish could be helping to hold the nut in place, attempting to remove the nut could chip the finish. Proceed with caution, ask questions or get professional help.
A guitar setup is adjusting the guitar to play and sound its best. Since an acoustic guitar is made of wood, variances in temperature and humidity and years of string tension can affect the setup, as can changing to lighter or heavier string gages.
Parts of the guitar: body, bridge, bridge pins, strings, fretboard, headstock, tuners. Part of the guitar that are affected with a setup: neck, truss rod, saddle, nut.
A basic setup consists of adjusting the neck relief, action and nut height.
WHAT IT IS:
The neck relief is the curvature of the neck that allows you to press the string at a fret and the string won’t buzz at the next fret. Excessive neck relief will result in high action, but the neck relief is not the only cause of high action.
The action is the distance between the strings and the 12th fret. High action makes the guitar very hard to play and will pull the strings out of tune when they are fretted.
The nut height (also known as nut action) affects how easily chords can be played in the first few frets. It will affect the string action to a small degree.
WHAT & HOW TO CHECK:
The neck relief is checked by holding the string down at the first and 14th frets (last fret before the body). Holding down the first fret takes the nut out of the equation. There should be a very slight gap at the 7th fret, .005” to .008”, about the thickness of 2 pieces of paper. Checking the low E and high E should be sufficient.
The action is measured at the 12th fret with the string held down at the first fret; again it takes the nut out of the equation. I like to see between 5/64” and 3/32” for the low E. Over 1/8” makes the guitar very hard to play. The high E string action should be 1/64” lower than the low E string, so I like to see 1/16” to 5/64”. The action for the other strings should taper from the height of the low E down to the high E.
Assuming the neck relief has been properly set, the cause of high action is typically a bad neck angle; the neck is pulled upward by string tension over time. The neck angle can be checked by laying a straight edge (I use a 25” one) on the fretboard. The end of the straight edge should be at the top of the bridge or slightly above it. If the straight edge ends below the bridge the neck angle is bad. It’s possible the neck is bowed (not related to neck relief) and the straight edge will only contact the neck at the first & last frets, throwing off the neck projection measurement. Typically that’s a guitar badly needing a neck reset.
The nut height is checked by pressing the string at the 3rd fret. There should be a very small gap at the 1st fret, checked by pressing directly on the first fret and feeling just a little movement, it should be very hard to see but you should feel and hear the string hit the fret. All strings need to be checked.
HOW TO ADJUST IT:
If the neck relief is too great (typical in guitars that haven’t been adjusted in a long time), it is adjusted by turning the nut on the truss rod. The truss rod nut is either in the head stock (covered by a plate) or inside the guitar. Typically a 4mm or 5mm Allen wrench is required. Many times the truss rod will be loose and need to be turned until resistance is felt, then checked again. The guitar must be tuned to pitch before and during a truss rod adjustment, the tension of the strings will affect the curvature of the neck. Turning clockwise will decrease the necks curvature, counterclockwise will increase it. Once some resistance is felt while adjusting, turn 1/4" of a turn, tune the guitar to pitch and check the neck relief again. If the truss rod nut won’t turn or takes an extreme amount of pressure, see a professional, over torqueing it could damage the truss rod or the neck.
The action is adjusted by changing the height of the saddle, either sanding the bottom or adding material. The neck relief must be properly set first. The amount of material to be added or removed from the saddle is double of the required change at the 12th fret, the 12th fret is halfway between the nut and the saddle. There is typically 1/8” (or less) of saddle sticking out of the bridge so the maximum adjustment would be 1/16” at the 12th fret. But you have to leave some of the saddle above the bridge so the adjustment would be less than 1/16”. Lowering the height of the saddle changes the angle between the bridge pins and the saddle, which is called the break angle. The break angle provides the force of the strings pressing on the saddle; a very shallow break angle will reduce the transmission of sound from the strings to the guitar top. The bottom of the saddle must be square to the sides otherwise the contact surface touching the bottom of the slot in the bridge is greatly reduced, reducing the efficiency of sound transmission from the strings.
Typically as a guitar gets older the tension of the strings causes the neck to bend upward (different than the curvature of the neck relief) and sometimes will cause the end of the fretboard to push into the top of the guitar. Adjusting the height of the saddle can help this, but eventually the neck angle becomes too great and a neck reset is required. A neck reset removes a triangle of material from the heel of the neck (where it contacts the guitar body) to bring it back into proper alignment. Most guitars have glued on necks, making this very difficult and expensive.
Something else that affects the action is the angle of the bridge and the area of the top behind the bridge. Over time the tension of the strings can also cause the back of the bridge to lift, typically taking the top with it. This can also cause a bulge in the top behind the bridge called a belly. If the back of the bridge is lifted, that will increase the action. There are other internal problems that can cause this also, such as a loose brace. There are ways to flatten the bridge and top but that is beyond the scope of this guide. The bridge can also come unglued from the top, resulting in a gap under the bridge. In this case, the bridge will have to be removed and properly reglued, injecting glue into the gap will not fix it.
Adjusting the nut height (or nut action) requires special files to deepen the slots. If all the slots are too high you can remove the nut (typically held in with a little glue) and sand the bottom slightly. This sounds simple but a cheap nut could break when tapped to remove it, or the guitar finish could be helping to hold the nut in place, attempting to remove the nut could chip the finish. Proceed with caution, ask questions or get professional help.
