Drill for rock

Claim 1

A drill for boring rock in a boring direction comprising a boring head body arranged on one end of a drill shank and having a central axis and at least two wings radially extending in different radial directions and having surfaces pointing in said boring direction, an axial centering projection having an end which projects in said boring direction in front of said wings, said wings and said centering projection constituting carriers of cutter bodies having cutting edges, said cutter bodies being arranged eccentrically on radial outer ends of said surfaces of said wings, and on the end of said centering projection, respectively, said centering cutter body on said centering projection projecting radially from said central axis and having a centering point on said central axis pointing in said boring direction, said eccentrically arranged cutter bodies having radial inner ends disposed from said centering cutter body at radial distances such that parts of said surfaces of said wings located radially between said inner ends and said centering cutter body form breaker surfaces serving during drilling to break annular surfaces, unworked by said cutter bodies, of rock to be bored, said boring head having channel type surfaces positioned between said wings, said centering projection having an outer surface defining centering projection jacket lines, each of said channel type surfaces having at least one bottom jacket line extending longitudinally to the longitudinal axis of said boring head body and directly joining one of said centering projection jacket lines, and said bottom jacket line forming at least at its joining end an obtuse angle with respect to said one centering projection jacket line.