Abstract This paper considers the mechanisms of contact interaction of diamond-bearing composite materials (diamond cutting wheel segments) when cutting steel and concrete using scanning electron microscopy. It is established that an increase in the cutting ability of a diamond cutting wheel with an increase in the concentration of diamond grits in the diamond-bearing composite material of the segments is associated not only with an increase in the number of diamond grits on the segment surface, but also with a change in the mechanism of contact interaction of the diamond-bearing composition with the workpiece. It is established that an increase in grit size, even with a small change in concentration (from 17.5 to 25 rel. %) in the segment, changes the cutting ability of the tool. Diamond grits reduce the contribution of frictional interaction of the bond with the workpiece, and their higher concentration in the segment leads to a decrease in impact loads on the grit. When cutting a steel pipe, an increase in the concentration of diamond grits reduces the frictional component of the contact interaction of the diamond-bearing composite material with steel, reducing the thermal effect of frictional interaction, and an increase in their size helps to increase the strength of their fixation by the bond, leveling the influence of the thermal effect of frictional interaction of the bond with steel and the increase in its temperature in the frictional contact zone.