In this paper are presented the results of electrical discharge diamond grinding with with difference polarities for processing various materials and calculates geometric parameters of erosion holes. The purpose of the study is to determine the volume of holes during electrical discharge diamond grinding using the mathematical method of planning experiments. The experimental plans is a combination of statistical theory and mathematical model, which is very useful in the modelling and analysing the technical problems. As a result of experimental studies, a mathematical model of the volume of holes from electrical modes of the process of electrical discharge diamond grinding was built. The mathematical formula of geometric parameters of holes obtained can be used to determine the volume of holes for different electrical quantities of discharge diamond grinding. It is found that the most significant factors that affect the geometric parameters of holes are the voltage of the igniting pulse and the pulse duration. The dependence of electrical parameters on the hybrid grinding process is investigated. There is a certain volume of holes, at which the discharge acts most efficiently, and the process performance is the most optimal. During the operation of the pulse generator, it is preferable to maintain a certain value of geometric parameters of holes, which results in an unhindered release of metal, since the effect of electrical erosion increases.