Rock cutting tool

An apparatus for cutting away a rock face of a relatively hard rock of known compressive strength, such as for drilling large diameter subterranean holes or for removing rock at the earth's surface, comprising:

• a cutting head rotated about an axis and mounted for movement relative to a rock face, the cutting head being formed of a plurality of drilling members, at least one of the drilling members having an external surface, the drilling member having an axis of rotation coincident with the conical axis thereof;
• means for mounting each of said drilling members for rotation about its said axis of rotation;
• a plurality of spaced apart indentors secured to said drilling member external surface, each indentor having an end point, the indentors being adaptable to penetrate into the rock face upon the application of working force a distance P, and wherein said indentor end points are spaced a distance of not greater than 7 P apart;
• and
• wherein the apparatus includes means of applying to it a force moving the apparatus in a preselected direction of drilling, and wherein the apparatus is configured to attain a rock face configuration wherein the slope of the rock face relative to the direction of drilling is between 30.degree. and 60.degree..