Abstract: A rock drilling bit comprises a steel body defining a cutting face with hard material inserts press-fitted into preformed openings in the cutting face. The inserts have ends extending outwardly of the cutting face which perform the actual drilling or cutting operation. The face surface of the body is case hardened except for narrow continuous bands about each insert opening. A method particularly suited for forming the case hardened cutting face is also disclosed.

Abstract: A method of forming precision openings in hardened steel workpieces is disclosed. The method generally includes drilling nominal size openings in the workpiece while it is in a soft condition. Thereafter, sizing plugs formed from a material having a strength greater than that of the steel body during a predetermined range of temperatures are press-fitted in the openings. With the plugs in position, the body is heat treated to harden it. Subsequently, the plugs are removed and the resulting openings are found to be of an extremely uniform size without the wide variations present when hardening is performed without the sizing plugs.

Abstract: A rock drilling bit comprises a steel body defining a cutting face with hard material inserts press-fitted into preformed openings in the cutting face. The inserts have ends extending outwardly of the cutting face which perform the actual drilling or cutting operation. The face surface of the body is case hardened except for narrow continuous bands about each insert opening. A method particularly suited for forming the case hardened cutting face is also disclosed.