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 spiral flute tap includes a body having an axial forward end and an axial rearward end. The body has a cylindrical shank portion adjacent the axial rearward end, a threaded fluted portion adjacent the axial forward end, a non-threaded fluted portion between the cylindrical shank portion and the threaded fluted portion, and a central, longitudinal axis. The spiral flute tap further includes a plurality of helical flutes formed at a helix angle, HA, with respect to the central, longitudinal axis of the tap that continuously increases in magnitude in the threaded fluted portion. In other words, the lead of the plurality of helical flutes continuously decreases in magnitude in a rearward direction for a predetermined distance. In one example, the helix angle, HA, varies at a rate of between 0.5 degrees/mm to 4.0 degrees/mm. A method of making the spiral flute tap is also disclosed.

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 spiral flute tap includes a body having an axial forward end and an axial rearward end. The body has a cylindrical shank portion adjacent the axial rearward end, a threaded fluted portion adjacent the axial forward end, a non-threaded fluted portion between the cylindrical shank portion and the threaded fluted portion, and a central, longitudinal axis. The spiral flute tap further includes a plurality of helical flutes formed at a helix angle, HA, with respect to the central, longitudinal axis of the tap that continuously increases in magnitude in the threaded fluted portion. In other words, the lead of the plurality of helical flutes continuously decreases in magnitude in a rearward direction for a predetermined distance. In one example, the helix angle, HA, varies at a rate of between 0.5 degrees/mm to 4.0 degrees/mm. A method of making the spiral flute tap is also disclosed.

The present disclosure provides a variable helical composite tap, which includes a drill bit segment and a tap segment sequentially arranged, where a helical angle of the drill bit segment is greater than a helical angle of the tap segment, and a core thickness of the tap segment is greater than a core thickness of the drill bit segment. The helical angle of the drill bit segment from a drill tip to a connection end of the tap segment with the drill bit segment increases continuously. The helical angle of the tap segment from the drill tip to a drill handle increases continuously, and preferably, the core thickness from the drill tip to the drill handle increases continuously. Compared with the prior arts, the drill bit segment of the present disclosure has a greater helical angle and a better chips removal effect is produced in the drill bit.

The compound die includes a working surface with a coarse end for forming coarse threads and a fine end for forming fine threads. The coarse end has coarse crests and coarse roots thereon angled at a coarse thread pitch angle for the screw to be formed. The fine end has fine crests and fine roots formed into a working surface thereof at an angle matching a pitch angle for the fine threads of the screw to be formed. A transition is provided between the coarse end and fine end where each of the coarse roots is aligned with one of the fine roots. A screw such as a bolt is roll formed by first being rolled between a standard die parallel with the compound die and a course end of the compound die, followed by rolling between the standard die and the fine end of the compound die.