Abstract: A spiral end mill which can mill a substantially sharp inside corner of a work surface and attain a stable working accuracy for a long time. The spiral end mill has a hard sintered compact insert portion, a negative relief face a first circular land provided along the outer periphery of the insert portion, and a second circular land on the negative relief face so as to be continuous with the first circular land. The widths of the two circular lands may be the same as or different from each other, and the helix angle of a back line of the second circular land is less than that of the first circular land. A method of manufacturing the spiral end mill involves machining a relief angle in the outer periphery of the insert portion while changing the helix angle between the negative relief face and the rest of the outer periphery.

Abstract: A stick of composite materials comprises a hot-pressed super-hard head member containing higher than 50 vol % of a diamond powder and/or a high pressure boron nitride powder, and a supporting member which is bonded at one of its ends with the hot-pressed super-hard head member. The stick of composite materials is characterized in that:the bonding between the head member and the supporting member is formed during the hot press process of the head member;the stick is of an elongated form, preferably of a cylindrical form of which the sectional diameter or equivalent sectional diameter is not larger than 3 mm;the length of the head member is 0.3 to 2.0 mm in the axial direction of the stick; and thatthe supporting member is more than five times longer in its axial direction than the head member.The stick of composite materials is usable as a blank for the microdrill, micropunch and the head of the dot character printer.