The dynamic instability and related problems when turning high chromium cast iron (HCCI) with two polycrystalline cubic boron nitride (PCBN) tools in wide range of cutting speeds and feed rates were studied in the article. The tool wear mechanisms and specifics for both tools as a main criterion of appearance of process instability were investigated. In spite of the chatter-like surface of machined workpieces it was shown the dynamic stability of process by two method ‘0-1 test’ and determination of maximum Lyapunov exponent. Taking into account the strong periodicity of process with several clear harmonics it was concluded that such process is related to self-resonant phenomena.