Patent ID: 9138819
Filing Date: 2015-09-22
Classification: B23G,Y10T

Abstract:
1. A plastic deformation tapping tool comprising: inside diameter finishing edges; an external thread portion provided with a complete thread section; and a chamfered end section that is formed contiguously to said complete thread section having: wherein: at least one flute is formed so as to divide a crest of said external thread portion axially, in parallel with an axis O through said chamfered end section and said complete thread section, and only said complete thread section is formed with the inside diameter finishing edges defined by an inner wall surface of said flute functioning as a rake surface, so that the inside diameter finishing edges remove by cutting an apex of the crest of said internal thread, which crest is formed by said plastic deformation, said protruding parts in said complete thread section are provided with large-diameter protruding parts formed in parallel with the axis O to form the inside diameter finishing edges, and each of said at least one flute is formed such that one of opposite open-end edges of the flute which is on an upstream side of the flute as seen in a rotating direction A of the tapping tool is coincident with an angular position of said large-diameter protruding parts about said axis O, and portions of said large-diameter protruding parts which are remote from said flute about said axis O are removed to form said diameter finishing edges, said protruding parts in said chamfered end section constitute a plurality of linear arrays each of which consists of a plurality of protruding parts successively arranged in a direction parallel to said axis O and which are angularly spaced apart from each other about said axis O, said large-diameter protruding parts are offset in the rotating direction A of the tapping tool about said axis O with respect to said protruding parts in said chamfered end section, and each of said at least one flute is formed so as to correspond to said large-diameter protruding parts, in said relief parts which are located between said plurality of linear arrays of protruding parts in said chamfered end section, about said axis O, and said inside diameter finishing edges are formed along said one of the opposite open-end edges of each of said at least one flute, and are offset by a predetermined angle θ in said rotating direction A with respect to said protruding parts in said chamfered end section.