A fillet gauge is a tool used to measure the radius of a fillet, which is a rounded corner or edge. The radius of a fillet gauge is not a fixed value; instead, fillet gauges come in sets with various radii to accommodate different fillet sizes.

Each gauge in a set has a specific radius, and the user selects the gauge that best matches the fillet being measured.

To determine the radius of a fillet gauge, you must refer to the marking on the specific gauge. These markings will typically be in either millimeters (mm) or inches (in).

For more information on fillet gauges, you can refer to the following resources:

• Substech: Fillet Weld Gauge https://www.substech.com/dokuwiki/doku.php?id=fillet_weld_gauge