At present not only the final finish machining of plain steels can be performed with high-speed machining, but also hardened steels may be machined directly. However, the processing technology research has been laggard. For instance, few investigations are reported about the suitable cutter and processing experience in the high-speed-milling of hardened steel. This paper introduces the preliminary experimental investigation on the failure mechanism of uncoated carbides in high-speed-machining, the process adaptability of coated carbide in the high-speed-machining of hardened steels, and the effects of end milling cutter geometry and cutting regimes on tool life and machining quality.