One of major tasks of the reliability theory is the research of failures technical systems. Reliability of functioning of technological systems in a significant measure is defined by reliability of the cutting tool. The most adverse kind of failure is the destruction of the tool resulting in off-schedule equipment downtimes and the raised charge of a tool material. In this connection the task of forecasting and decrease of probability of the tool destruction in various conditions of operation is rather urgent

      In represented work the technique of a quantitative estimation of probability of the cutting tool destruction on parity of levels of its durability and working loading is developed and checked experimentally. This technique allows to predict the basic parameters of the tool reliability in various conditions of operation and to improve a choice of rational conditions of cutting tool operation for raising reliability of technological systems.

      The purpose of the presented work is creation of method of calculation of temperature of the cutting tool in the conditions of the unset heat exchange and also analysis on its foundation of influence of treatment terms on his thermal state.

      The input dates for formation of probabilistic models of failures are established ground of analysis of stochastic processes of a cutting tool edge deterioration and destruction.

      The main assumptions at mining probabilistic model of the tool failures in connection with achievement of marginal wearing the set of implementations of wearing on a flank surface is characterized by a normal distribution law at any moment of time. The time history of average values of wearing is described by a function which one with adequate accuracy within the limits of a zone of the natural wear can be adopted linear by constant speed of deterioration. In this case stability up to achievement of marginal wearing of a cutting blade is subject to a normal distribution law.

      The designed probabilistic models of failures allow ground of analysis of legitimacies of a random change in time of process parameters of deterioration and destruction of the cutting tool edge to create a technique of calculation of the main parameters reliability of a modular cutting tool and also to establish intercoupling of reliability parameters with processing conditions.

      TIn a case when a primary kind of the cutting tool failures is the achievement of marginal wearing the normative mean term of stability is determined on known relations introduced in the referential - normative literature. Thus the dispersion of stability is unsignificant and coefficient of its variation does not exceed 0,33.

      If there is the cutting tool failures bound with its destruction the mean term of stability in matching with normative is reduced and the coefficient of variation is increased. The created model allows to predict parameters most widespread for of the cutting tool Veibull law of distribution of parameters of non-failure operation and durability - period of stability and number of the periods of stability in various conditions of operation.

      In the present activity as the main parameter of the cutting tool reliability along with the mean term of stability the gamma - interest period of stability - time in cut is esteemed during which one the tool does not reach failure with given probability expressed in percentage. The introduced relations allow to establishing influencing parameters of processing on gamma - percentage stability of the tool with allowance for probabilities of its destruction.

      At designing of the tool and solution of a problem of selection of new design or technological version influencing properties of a wear resistance and strength on reliability parameters in the given operation conditions estimates. At exploitation of the tool and solution of a problem of selection of rational treatment schedules influencing cutting modes on parameters of reliability of the tool estimates at a given level of properties of the tool.

      Thus the designed technique with allowance for of parameters of stochastic processes of deterioration and destruction of a cutting edge tool allows to execute forecasting of the mean term of stability and its dispersion in the different operation conditions, to establish nature and parameters of a stability distribution law and also to select treatment schedules ensuring demanded reliability level.

      The experimental investigations of the cutting tool reliability are used for the substantiation of the cutting tool failure kinds and of the reliability parameter distribution law.

      On the basis of carried out theoretical and experimental researches of reliability the recommendations are developed at the choice of conditions of operation of the cutting tool ensuring any required guaranteed level of its reliability. Defining for the given conditions of manufacture the optimum level of parameters of reliability is possible to reach a peak efficiency of use of the cutting tool at the minimal expenses for its operation.