Abstract: The disclosed hammer comprises a power frame, having a working chamber for the deforming medium, a die block adapted to accommodate therein a blank and an impact head with a housing having fastened therein a hollow separating bush coaxial with the housing. Received concentrically within this bush is a sleeve enclosing a plunger mounted in this sleeve for vertical reciprocation, to define a working cylinder between the top end face of the plunger and the bottom of the sleeve. An annular space is defined by the housing of the impact head and the body of the separating bush, surrounding the working cylinder and communicating with the hydraulic hammer control system. The essence of the invention consists in that the working chamber for the deforming medium, has a built-in container having a bottom made of an elastic material. The container is mounted for cooperation of its bottom with the blank accommodated in the die block.