Drill rods made of hexagonal hot-rolled steel of 55C2, 3OHGSFA, 12XHZA, 30XMA, 28XGNZM, 40X2AUF and others break during perforator drilling. The rods break in the areas of shoulder, shank, cone part, as well as along the length of the main part of the hexagon. The most frequent breakages occur in the bump zone, which is obtained by hot-drilling on boring machines.