US Patent 11890687 Milling tool and workpiece machining method

A milling tool is configured from a shank part and a head with a cutting edge that is provided on the leading end of the shank part. The head comprises an expanding diameter section, the diameter of which expands gradually from the base end that contacts the shank part in the direction of the leading end, and a decreasing diameter section, the diameter of which gradually decreases from the maximum diameter section in the direction of the leading end. At least one cutting edge is provided on each of the expanding diameter section and the decreasing diameter section.