TOOL FOR CUTTING FEMALE THREAD (SCREW TAP) Russian patent published in 1997 - IPC

FIELD: metal cutting, namely tools for thread cutting. SUBSTANCE: screw tap has working part consisting of inlet and sizing portions and stem. Said working part includes cutting bits and recesses between them. Said recesses are arranged along said bits for receiving chip and supplying cutting fluid. Bits of inlet portion have relief angles more than 5 degrees and flat back surfaces. Minimum number of cutting bits is equal to 2. Width of bits is selected in range consisting 0.02-0.2 of tap outer diameter; diameter of bit core is no more than 0.35 of tap outer diameter. Length of inlet portion is equal at least to half-length of the whole working part. EFFECT: improved design. 7 cl, 3 dwg