Rock bit roller cutter and method therefor

Claim 2

In the manufacture of rock bit roller cutters to be mounted on friction journals, wherein a cutter comprises a roller body having pural peripherally distributed holes, and hard metal inserts press-fitted into said holes in outwardly projecting relation, the steps of forming the roller body of a maraging steel comprising a nickel-cobalt alloy, forming said body holes therein, then age-hardening the roller body to a hardness of not less than 50 R c under conditions maintaining dimensions of the formed holes and thereafter press-fitting hard metal inserts into said roller body holes.

Claim 3

The method according to claim 1 in which said insert-receiving holes are formed to their final dimension in the roller body prior to hardening.

Claim 4

The method according to claim 1 including also press-fitting said inserts in the holes therefor prior to hardening the roller body so that the body is hardened with the inserts in place therein.

Claim 5

The method according to claim 1 including also providing a bearing surface on said roller body comprising aluminum bronze heat treated to have a continuous phase of a first and relatively lower degree of hardness between 25 and 30 R c and a particulate discontinuance phase of a second and relatively higher degree of hardness between 40 and 45 R c , the lower degree of hardness being less and the higher degree of hardness being greater than that of a friction journal upon which the roller body is to be mounted.

Claim 6

The method according to claim 1 including effecting hardening of the roller body by heating at 950° F for about 3 hours and cooling without quenching.

Claim 7

In a rock bit structure, a rock bit roller cutter body having a peripherally distributed series of hard metal inserts press-fitted into holes therein in outwardly projecting relation, said roller body comprising an age-hardened nickel-cobalt alloy selected from the group consisting of the alloy which consists essentially in percent by weight of ______________________________________ Ni 17 to 19% Co 7 to 8.5% Mo 4.6 to 5.2% Ti 0.3 to 0.5% Al 0.05 to 0.15% C 0.03% Fe the balance to 100%, ______________________________________ and the alloy which consists essentially in percent by weight of ______________________________________ Ni 17 to 19% Co 7 to 8.5% Mo 4.6 to 5.2% Ti 0.3 to 0.5% Al 0.05 to 0.15% C 0.03% Fe the balance to 100% ______________________________________

Claim 8

In a rock bit structure, a rock bit roller cutter body having a peripherally distributed series of hard metal inserts press-fitted into holes therein in outwardly projecting relation, said roller body comprising an age-hardened nickel-cobalt alloy selected from the group consisting of the alloy which consists essentially in percent by weight of ______________________________________ Ni 17 to 19% Co 7 to 8.5% Mo 4.6 to 5.2% Ti 0.3 to 0.5% Al 0.05 to 0.15% C 0.03% Fe the balance to 100%, ______________________________________ and the alloy which consists essentially in percent by weight of ______________________________________ Ni 17 to 19% Co 7 to 8.5% Mo 4.6 to 5.2% Ti 0.3 to 0.5% Al 0.05 to 0.15% C 0.03% Fe the balance to 100% ______________________________________