method and apparatus for sharpening a tool , such as a drill bit . a tool sharpener includes a tool holder subassembly which retains and presents the tool against a grinding wheel subassembly . a sensor locates a cutting edge of the tool while the tool is retained by the tool holder . a circuit , preferably comprising a programmable processor , determines a web thickness of the tool from the located cutting edge . the cutting edge is preferably located by detecting at least first and second points at different radii along the cutting edge . a cross - feed subassembly preferably moves the sensor into position , and the tool holder subassembly preferably rotates the tool to facilitate detection of each of the at least first and second points . the tool holder subassembly thereafter presents the tool against the grinding wheel subassembly in response to the determined web thickness of the tool .