Abstract A masonry core drilling bit for cutting through cast concrete into preplaced utility conduit cells beneath the surface. The bit has two concentric, axially offset, end cutting faces on a unitary cutter head arranged at the end of a hollow shank for simultaneously cutting through concrete and through the metal cover of the embedded cell while, at the same time, providing an enlarged hole in the concrete to accept an insert for a utility outlet. The cutter head of the bit contains 5 to 60 volume per cent uniformly dispersed diamonds in a matrix of substantially pure iron powder, or an iron powder containing 20-80 vol. percent WC, infiltrated during fabrication with a relatively low-melting alloy. Spaced diamonds are provided along the internal and exterior cylindrical surfaces of the cutter head of the bit.
The drill bit of claim 1 wherein the bit shank and the cutter element body are provided with coextensive axial bores, and further comprising diamonds mounted in the surface of the axial bore in the cutter element body to form a cylindrical internal cutting surface.
Claim 2
Dependent Claim
42 words
The drill bit of claim 2 wherein the diamonds in the cylindrical external and internal cutting surfaces are placed in axially aligned rows equally spaced about the surfaces, and the dispersed diamonds are held in a matrix of consolidated and infiltrated powder.
Claim 3
Dependent Claim
41 words
The drill bit of claim 2 wherein the first and second flat cutting faces have substantially equal cutting areas, and wherein the second cutting face is provided with at least one radially-oriented notch across the entire width of the cutting face.
Claim 4
Dependent Claim
53 words
The drill bit of claim 3 wherein the matrix of consolidated and infiltrated powder comprises fine spherical iron powder having an average particle size between 5 and 10 Mu infiltrated with an alloy which melts below 1800*C and wherein the dispersed diamonds therein occupy 5-60 volume per cent of the cutter head body.
Claim 5
Dependent Claim
45 words
The drill bit of claim 3 wherein the surface mounted diamonds and the dispersed diamonds are each about 125 to 150th of a carat, and wherein the dispersed diamonds are uniformly distributed throughout about two-thirds of the cutter head body farthest from the bit shank.
Claim 6
Dependent Claim
38 words
The drill bit of claim 3 wherein the infiltrant alloy consists essentially of, by weight, 48 percent Cu - 42 percent Zn and 10 percent Ni, and wherein the alloy bonds cutter head body to the bit shank.
Claim 7
Dependent Claim
33 words
The drill bit of claim 3 wherein the matrix of consolidated and infiltrated powder further comprises up to 80 volume per cent angularly-shaped tungsten monocarbide powder having a particle size of -200 mesh.