A thread forming tap including a complete thread portion and a leading portion that are provided with an external thread. A thread ridge of the external thread has, in an axial cross section, a triangular shape that is defined by a pair of flanks located on respective opposite sides in an axial direction, such that each of the flanks is inclined by a predetermined flank angle corresponding to a shape of a valley of an internal thread to be formed. A sharp crest is provided in a top portion of the thread ridge at least in the leading portion, and has, in the axial cross section, a triangular shape that is defined by a pair of side surfaces located on respective opposite sides in the axial direction, such that each of the side surfaces is inclined by an inclination angle that is larger than the flank angle.

A thread forming tap including a complete thread portion and a leading portion is to be screwed into a prepared hole provided in a workpiece so as to cause an inner circumferential surface of the prepared hole to be plastically deformed for thereby forming an internal thread corresponding to the external thread provided in the complete thread portion. A screw thread of the external thread has a leading flank and a trailing flank, which are to be positioned on a front side of the trailing flank and on a rear side of the leading flank, respectively, when the thread forming tap is screwed into the prepared hole. The screw thread is shaped such that, in the leading portion, an indentation depth into the workpiece made by the leading flank is smaller than an indentation depth into the workpiece made by the trailing flank.

A pipe-tapered-thread machining spiral tap includes a tapered thread portion that is circumferentially divided by flutes into a plurality of lands. Each of at least one of the lands has a cutting edge that extends along a corresponding one of the flutes. The flutes are made of a plurality of spiral flutes that are three, four or five spiral flutes each having a helix angle that is not smaller than 30 and smaller than 50. A flute width ratio AG/(AG+AL) is 0.3-0.5, where AG represents a central angle which is subtended by each of the flutes and which is defined at a center corresponding to the rotation axis in a cross section that is perpendicular to the rotation axis, and AL represents a central angle which is subtended by each of the lands and which is defined at the center in the cross section.

A cutting tap includes thread ridges, roots formed between the respective axially adjacent pairs of thread ridges, and a plurality of deburring thread grooves arranged at a constant pitch toward the axial front side of the cutting tap from the rearmost ones of the roots in which the deburring thread grooves are formed, and formed such that a groove bottom diameter of the deburring thread grooves gradually decreases toward the axial front side of the cutting tap. The respective deburring thread grooves have groove bottom diameter reliefs by which the groove bottom dimeter gradually decreases from the front side toward the rear side of each deburring thread groove in the rotation direction of the cutting tap, the groove bottom diameter reliefs being set to be larger than effective diameter reliefs of the thread grooves.

In one aspect, thread forming taps are described herein. In some embodiments a thread forming tap comprises a shank disposed at a first end adapted to engage a tool holder and an elongated working portion disposed at a second end. The working portion comprises at least one helical thread and a plurality of longitudinally-extending linear grooves. The longitudinally-extending linear grooves intersect the helical thread forming a plurality of lobes, wherein adjacent lobes differ from one another in relief type and/or relief rate.

A multi-sectional drilling and tapping apparatus includes a shank, a drill and a tap that are made in one piece. The shank is formed at an end while the drill is formed at another end. The drill includes a small section formed between a tip and a large section. The drill further includes helical blades extending to the shank from the tip. The tap includes helical ribs each extending from a corresponding one of the helical blades and groups of tooth-shaped blades each evenly arranged along a corresponding one of the helical ribs. The tap includes a diameter larger than that of the large section of the drill.