Patent attributes
Flutes defining inside diameter finishing edges are formed in middle portions of relief parts arranged in three linear arrays which are located between a plurality of linear arrays of protruding parts in a chamfered end section, about an axis 0, and the inside diameter finishing edges are formed along one of opposite open-end edges of each flute which is located on an upstream side of the flute as seen in a tap rotating direction A, and are offset by a predetermined angle θ in the tap rotating direction A with respect to the protruding parts in the chamfered end section. Accordingly, all of the plurality of linear arrays of protruding parts in the chamfered end section can be used to form the internal thread by plastic deformation of an inner circumferential surface of a hole to be tapped.
