Abstract: A cutting tap that has an elongate tap body with a fluted section at the axial forward end thereof wherein the fluted section includes a chamfered fluted section and a finishing fluted section. Each cutting thread in the chamfered fluted section has a cutting face disposed at a cutting face angle that becomes more negative the more axially rearward the cutting thread is from the axial forward end of the chamfered fluted section. Each cutting thread in the finishing fluted section has a cutting face disposed at a finishing cutting face angle that is essentially equal. The finishing cutting face angle is more negative than the cutting face angle for the cutting thread at the axial rearward termination of the chamfered fluted section.

Abstract: A coated carbide tap comprises a substrate consisting of tungsten carbide cemented with 12 to 16% by weight cobalt with additions of small amounts of transition metal carbides added to restrain grain growth, and may also contain low levels of impurities that might be picked up during processing. The substrate is coated with a layer of metal nitrides, carbides, carbonitrides, borides and/or oxides, the metal being chosen from one or more of the following: aluminum, silicon and the transition metals from Groups IVa, Va, and VIa of the Periodic Chart. The coating may comprise a monolayer and/or alternating layers optionally with varying chemical composition.