Patent ID: 7137461

Claim:
A masonry or rock drilling tool suitable for use with a rotary hammer comprising: a drilling head at a forward end of the tool, a forwardly extending cutting plate formed with said drilling head, first and second opposing axially extending channels formed on the circumferential periphery of said drilling head; a clamping shank at a rearward end of the tool suitable for fitment within a tool holder of a rotary hammer; an intermediate helical conveying portion extending between the drilling head and the clamping shank, at least four helically extending flutes separated by corresponding helically extending webs formed on said intermediate helical conveying portion; a central chiselling dome and a pair of cutting edges extending radially outwardly from the chiselling dome formed on said cutting plate, each cutting edge has a trailing relief face and an acute angle between the relief face and the longitudinal axis of the tool varies from a radially inner portion to a radially outer end of each cutting edge; and said first axially extending channel extends axially rearwardly from a forward facing face of the drilling head into a plurality of the at least four flutes and said second axially extending channel extends axially rearwardly from the forward facing face of the drilling head into a different plurality of the at least four flutes.