Radius Gauges — Lutherie Encyclopedia

Radius GaugesType: toolA set of curved templates for verifying and setting the fretboard radius during construction and fret leveling.## Description Radius gauges (also called fretboard radius gauges) are thin, rigid templates with precisely curved edges matching standard fretboard radii. A typical set includes gauges for common radii: 7.25 inches, 9.5 inches, 10 inches, 12 inches, 14 inches, 16 inches, and 20 inches. They are usually made from laser-cut steel, aluminum, or acrylic. Each gauge is labeled with its radius and held against the fretboard to check for a matching curve. ## Use in Lutherie Fretboard radius refers to the curvature across the width of the fretboard, which affects playability and string action. During construction, the luthier sands or planes the fretboard to a specific radius, checking frequently with the appropriate gauge. After fretting, the radius gauges verify that fret tops follow the same curve. During setup, they confirm the saddle radius matches the fretboard radius. They are also used when building or adjusting nut slots to ensure the string heights follow the correct curve. ## Selection Guide Purchase a set that covers the radii you commonly build. Sets of 9 to 12 gauges are available from Stew-Mac, Hosco, and various Amazon sellers. Stainless steel gauges are the most durable and precise. Notched versions (with cutouts for strings) allow checking the radius on a strung instrument. Budget 15 to 40 dollars for a complete set. ## Tips - Hold the gauge perpendicular to the fretboard and look for light gaps between the gauge and the surface. Even light gaps indicate high or l…