Abstract: A method of producing a nitrided cut tap that includes a nitrogen diffusion layer. The method includes (a) a nitriding step for forming the nitrogen diffusion layer in which nitrogen atoms contained in an atmospheric gas are diffused from a surface of a base material of the cut tap under heat, such that the nitrogen diffusion layer has a thickness ranging from 10 ?m to 30 ?m; and (b) a honing step for rounding a cutting edge portion by colliding abrasive particles against a local part of the cutting edge portion of the base material of the cut tap that has been subjected to the nitriding step, such that a difference between a thickness of the nitrogen diffusion layer in the cutting edge portion and a thickness of the nitrogen diffusion layer in flank and rake surfaces sandwiching the cutting edge portion, is not larger than 5 ?m.

Abstract: Provided is a rolling die that increases the durability of a nitrided molded surface. The rolling die (1) includes a tool base material that is made of steel and has a molded surface (2) on which a plurality of working teeth (10) is formed. The tool base material includes a nitride layer (15) in which nitrogen is diffused. The nitride layer (15) is disposed to reach a position that is 20 to 70 ?m in depth from the molded surface (2). The molded surface (2) has a surface hardness of at least 1100 HV. The rate of depth change from the depth (D1) of the nitride layer (15) at crests (11) of the working teeth (10) to the depth (D2) of the nitride layer (15) at roots (13) of the working teeth (10) is not higher than 30%.