A hybrid threading tap includes a reamer portion and a thread cutting portion having a plurality of cutting teeth. The thread cutting portion is arranged with the reamer portion along the longitudinal axis. The reamer portion is configured to be advanced within a hole of a workpiece to plastically deform and expand the hole to an expanded hole and provide the expanded hole with a zone of residual compressive stress. The plurality of cutting teeth is configured to cut a threading into the expanded hole within the zone.

A method of making a cutting tap includes: providing an elongate tap body having an axial forward end, an axial rearward end and a central longitudinal axis; securing the axial rearward end of the tap body in a grinding machine; and forming in the axial forward end of the tap body a correction grind and a main flute in one continuous grinding operation. A cutting tap made by the invention is also provided.

A method of making a cutting tap includes: providing an elongate tap body having an axial forward end, an axial rearward end and a central longitudinal axis; securing the axial rearward end of the tap body in a grinding machine; and forming in the axial forward end of the tap body a correction grind and a main flute in one continuous grinding operation. A cutting tap made by the invention is also provided.

A hybrid threading tap includes a reamer portion and a thread cutting portion having a plurality of cutting teeth. The thread cutting portion is arranged with the reamer portion along the longitudinal axis. The reamer portion is configured to be advanced within a hole of a workpiece to plastically deform and expand the hole to an expanded hole and provide the expanded hole with a zone of residual compressive stress. The plurality of cutting teeth is configured to cut a threading into the expanded hole within the zone.

A thread forming tap includes a partial thread. The partial thread is provided, in the axis direction view, with a protrusion formed so as to protrude in the radial direction and a clearance section formed so as to have a smaller diameter than the protrusion, and as a result of the foregoing, if a thread forming tap rotates in a state where the inner circumferential surface of a pilot hole and the partial thread come into contact, the protrusion of the partial thread can be caused to engage with the inner circumferential surface of the pilot hole. Due to this configuration, rubbing in a state where the partial thread is pressed against the inner circumferential surface of the pilot hole can be suppressed, and as a result, chipping of the partial thread can be prevented.

A thread forming tap includes a partial thread. The partial thread is provided, in the axis direction view, with a protrusion formed so as to protrude in the radial direction and a clearance section formed so as to have a smaller diameter than the protrusion, and as a result of the foregoing, if a thread forming tap rotates in a state where the inner circumferential surface of a pilot hole and the partial thread come into contact, the protrusion of the partial thread can be caused to engage with the inner circumferential surface of the pilot hole. Due to this configuration, rubbing in a state where the partial thread is pressed against the inner circumferential surface of the pilot hole can be suppressed, and as a result, chipping of the partial thread can be prevented.

A cutting tool body includes a first member and a second member, both having a substantially cylindrical shape, and arranged such that a tool body central axis coincides with a central axis of each of the first and the second members. The first member has a tool characteristic of a first magnitude and the second member has the tool characteristic of a second magnitude, different from the first magnitude. The cutting tool body includes a transition member arranged between the first and second members and connected at a first end to the first member and at a second end to the second member. The tool characteristic in the transition member is of the first magnitude at the first end and of the second magnitude at the second end. The transition member has a transition region between the first and the second ends in which the tool characteristic transforms from the first magnitude to the second magnitude.

A cutting tool body includes a first member and a second member, both having a substantially cylindrical shape, and arranged such that a tool body central axis coincides with a central axis of each of the first and the second members. The first member has a tool characteristic of a first magnitude and the second member has the tool characteristic of a second magnitude, different from the first magnitude. The cutting tool body includes a transition member arranged between the first and second members and connected at a first end to the first member and at a second end to the second member. The tool characteristic in the transition member is of the first magnitude at the first end and of the second magnitude at the second end. The transition member has a transition region between the first and the second ends in which the tool characteristic transforms from the first magnitude to the second magnitude.

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.

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.