At present a significant problem at the production of high-precision machinery and devices is the ensuring of stability of quality specified parameters and increase of working productivity. The simultaneous achievement of these values may be obtained only at the expense of the destination of optimum modes and methods of manufacturing operations control for that there were necessary adequate mathematical models. The existing engineering processes are formed on determined procedures without taking into account a stochastic nature of a process and the interference of chemical and mechanical phenomena in the area of working. In the paper the mechanism of allowance removal at finishing with abrasive pastes having in their composition as fillers the surface-active matters as a factor defining the effectiveness of a finishing procedure is investigated. A process mathematical model is developed allowing the computation of material removal at any time at different algorithms of modes changes including parameters of a contact area, a current state of a surface layer in a blank. A model formed taking into account the process of passivation, machine cutting, takes into account a stochastic character of a process and allows estimating differentially the impact of separate factors upon material removal.