"The article presents results of the study of volume-stressed state of the supporting elements of bit by using polarization-optical method of stress analysis. In order to improve bit design one requires accurate and complete information about the stressed state of its basic elements. Authors applied the technology of "freezing" (fixation) the stress-strain state of the model of considered construction of elements of roller-cone drill bits. Polarization-optical method used for determining the stresses in the bit support is particularly effective in the study of stress concentration for the selection of the optimal shape, size and mass of structures during their design. Using this information one can increase reliability of the basic elements by reducing stress in areas of its concentration. The developed method of research on the "frozen" models gives an overall picture of the stress state of bit elements under axial load. In this case, the tangential stresses in the structure is insignificant, however, the maximum meridional stresses exceeding the yield point occur in the 1st leg in a zone of connection with the cone pin. In this zone elastic-plastic deformations occur, the value of which one can reduce, for example, by increasing the coupling radius of respective surfaces."