Abstract: A two-surface constrainable tool has two retaining surfaces by which the two-surface constrainable tool retains itself on a spindle (10) of a machine tool. The two-surface constrainable tool comprises: a bottom grip taper shank (14) having a taper part (15) having a first retaining surface and capable of being closely fitted in a taper bore (12) formed in the spindle (10), and a flange (16) provided in one end surface (16a) thereof facing the end surface (10a) of the spindle (10) with a groove (18); and a collar (20) to be interposed between the end surface (16a) of the flange (16) and the end surface (10a) of the spindle (10), consisting of two symmetrical segments (20a, 20b) having ridges (22a, 22b) to be fitted in the groove (18) of the flange (16), and a second retaining surface to be brought into close contact with the end surface (10a) of the spindle (10). The bottom grip taper shank (14) retains itself by the first and the second retaining surface on the spindle (10).

Abstract: An end mill comprises an arbor, a tool body attached to an end of the arbor, and throw-away chips detachably attached to an end face of the tool body. Each throw-away chip has a cutting edge having a peripheral circular cutting edge section for shaping, and an end straight cutting edge section for end milling.