Using Radius Gauges for an Optimal Guitar Setup

Using Radius Gauges for an Optimal Guitar Setup

To measure the fretboard radius of your guitar, you’ll need a tool called a radius gauge. A guitar radius gauge is used to ensure the radius of your strings matches the radius of your fretboard in order to  optimize your guitar’s playability.  Before using radius gauges, we recommend that you place your guitar on a flat padded surface with good lighting (laying a large towel on a counter top or table works well for this purpose).  A rolled towel can also be placed under the neck for stability if you don’t own a neck rest.  If you are already sure of your fretboard’s radius, skip to Step 2.

Step 1 – Determine the Radius of your Fretboard.  This is one-time, trial-and-error process by placing your gauge directly on the fretboard (I prefer doing so near the 12th fret where it’s easier to get under the strings). Electric guitars tend to have a more acute radius (in the neighborhood of 7.5 to 10) while most acoustics tend to be flatter (12 and above).  Most classical guitars have a flat fretboard so gauges are unnecessary. If you own multiple guitars, you might want to jot down the radius of each for future reference.

Step 2 – Set Desired String Action.  Using a precise ruler (a String Action Gauge is ideal for this purpose), ensure that you are happy with the string height of the of your Low and High E strings.  General guidelines are shown below—but action is ultimately your own preference based on your style of play, the characteristics of your guitar including the type of strings in use. Before moving on to Step 3, play each note on the high and low strings up and down the fretboard to ensure there is no fret buzz.  If you are experiencing fret buzz within or above normal action tolerances, you may have other setup corrections which need to be addressed (e.g., checking your fretboard and ensuring its flat (adjust with truss rod as needed), smoothing frets which sit up too high, etc.).

Step 3 – Set B, G, D and A String Heights.  

Electric Guitars:  Using the gauge which best matches the radius of your guitar’s fretboard (as determined in Step 1), gently lay the gauge across the top of the strings at approximately the 12th fret.  Without applying any downward pressure, ensure the gauge is touching both the Low E and High E strings (if not, lower height of the middle strings which are preventing the gauge from sitting on the low and high strings.  Next look for any subtle gaps where your B, G, D and/or A strings are not touching the underside of the gauge and carefully increase the height of those strings until they just touch the underside of your gauge.  When properly adjusted, all of your strings should just be touching the underside of the gauge (when no downward pressure is placed on the gauge).  

Acoustic Guitars:  Using the gauge which best matches the radius of your guitar’s fretboard (as determined in Step 1), place the gauge directly on top of your saddle. If the saddle radius differs, remove the saddle and carefully sand top arc until it matches the radius of the fretboard (I prefer using 150 grit sandpaper for saddle adjustments). To achieve your desired string action, you might also need to sand the bottom of the saddle (to lower action), or place a shim across the entire underside of the saddle to uniformly raise the string height of all strings (a flat, thin piece of plastic or cardstock paper can be used for this purpose). Note: If your saddle is still too low or otherwise in poor condition, consider starting fresh with a new bone saddle and sanding it to your desired action height and radius. A bone saddle can go a long way in improving your guitar’s tone and sustain as well.