The BARCOR CHAMFER GAGE is a precision instrument designed specifically to measure the top (major) diameter of a chamfer, countersink, center drill, or tapered hole. Merely press the spring loaded, conically ground, precision 3-blade Gaging Plunger into the chamfer or countersink and instantly read the dial in .001" or .01mm/.02mm diameter increments. The CHAMFER GAGE is a direct reading gage. No Setting, Master (Standard) or look-up chart is required. To "Zero" the gage or check the setting, press the base of the gage against any flat ground surface and adjust the dial to read the "Set To" number stamped on the back.