Threadmilling tool

A threading apparatus comprising:

• a thread cutting insert having a mount portion with an axis and only two arms that project in opposite directions from said mount portion, each arm having an outer border and a pair of opposite sides extending largely radially away from said axis, said outer border having a plurality of thread cutting teeth spaced parallel to said axis to cut a plurality of thread turns at the same time;
• said mount portion having six substantially flat locating surfaces, including two primary locating surfaces that extend parallel to each other and four secondary locating surfaces that each extends at least about 90.degree. to one of said primary locating surfaces, with each secondary locating surface extending parallel to another locating surface;
• an elongated insert holder having an axis of rotation, said holder having first and second positioning surfaces for respectively engaging a primary and secondary locating surface of said insert while one of said arms projects largely radially from said holder axis, said holder having a recess extending along said holder axis and one of said insert arms lies in said recess but out of contact with the walls of said recess.

A threading apparatus comprising:

• an insert which has a cross-section forming a mount portion with a plurality of straight insert locating sides lying on the sides of an imaginary hexagon that has an axis, except that two opposite sides of said hexagon are longer than the other four shorter sides, said cross section having a radially outwardly extending arm at each of two corners of said imaginary hexagon, each arm extending from the imaginary intersection of a pair of said shorter sides of the hexagon, with each arm having an outer border and a pair of opposite sides that extend in a largely radially outward direction from the axis of said hexagon, and with each arm forming a cutting edge at the intersection of the outer border and each of the sides of the arm;
• each of said cutting edges forming at least one thread-cutting tooth;
• a tooth holder for holding said insert, said tool holder having walls forming, in cross-section, a pair of straight holder positioning sides that abut a pair of said insert locating sides, and said tool holder having a clamp that presses a pair of said insert locating sides firmly against said pair of said holder positioning sides, whereby to accurately locate said insert.