A print hammer actuating assembly for a high speed printer, wherein a one-piece magnetic block is secured to a first core structure to provide a second core unit which includes a multiplicity of integral pole pieces. The block is of elongated construction and it has a series of spaced apart projections extending transversely to its longitudinal axis to provide discrete pole pieces. A series of elongated bores extend transversely to the longitudinal axis of the block in alignment with each of the projections. A hammer actuator assembly is disposed in each bore. A bucking coil contiguously surrounds each of the projections to provide a series of selectively energizable magnetic fields for operating each hammer actuator. With such an arrangement, the single pole piece block may be readily manufactured and assembled, at reduced cost. In addition, the working distance between tips of hammers and the paper may be readily adjusted by means of a single operation, thus affording a considerable saving in field maintenance time.