Thickness Gauge — Lutherie Encyclopedia

Thickness GaugeType: toolA deep-throat gauge for measuring plate thickness at any point across the width of a guitar top or back.## Description A thickness gauge (also called a plate thickness gauge or lutherie caliper) has an exceptionally deep throat, typically 100mm to 300mm, allowing it to reach the center of a guitar top or back plate for thickness readings. The gauge uses a dial indicator mounted on a rigid C-frame with flat contact anvils on both jaws. Resolution is typically 0.01mm or 0.001 inches. Some models use a magnetic base with a plunger-style indicator. ## Use in Lutherie During the thicknessing process, the luthier reduces the guitar top and back plates to their target thicknesses, which directly affect the instrument's tone and structural integrity. A standard caliper cannot reach the center of a plate, but a deep-throat thickness gauge can measure anywhere on the surface. The luthier typically maps a grid of measurement points (15 to 20 points) on the plate, recording the thickness at each location to ensure even graduation. Target thicknesses vary by tonewood species, with spruce tops typically finished to 2.5mm to 3.0mm and rosewood backs to 2.0mm to 2.5mm. ## Selection Guide The LMI and Stew-Mac thickness gauges are purpose-built for lutherie and offer 200mm to 300mm throat depth. Alternatively, a standard dial indicator can be mounted on a shop-built deep-throat frame. The gauge must be rigid enough to avoid flexing, which causes false readings. Budget 40 to 120 dollars for a commercial lutherie thickness gauge. ## Tips - Calibrate the gauge by measuring a known-thickness refere…