A method of manufacturing drilling crowns for cylindrical diamond drilling tool bits affords a waste-free fabrication of the drilling crowns impregnated with diamond particles. In a first step an annular axially extending middle or intermediate zone impregnated with diamond particles is joined at each of its opposite end by sintering to a different annular metal end zone. In a second step the intermediate zone is laser cut to form two similar drilling crowns with circumferentially spaced teeth. The teeth form diamond segments providing economical fabrication and a high quality connection with the end zones.

Disclosed is an improved implement comprising a cemented carbide supported composite abrasive compact which is brazed to a cemented carbide substrate with a brazing filler metal having a liquidus substantially above 700.degree. C. The composite compact preferably is a composite polycrystalline diamond compact. The brazing filler metal is a brazing alloy having a liquidus not substantially above 1,004.degree. C. and which has the following composition, by weight: Au: 18-39.5% Ni: 3.5-14.5% Pd: 2.5-10.5% Mn: 7.5-9.0% Cu: Balance.

A cutting member for rotary drill bits consists of a carrier member with a supporting face which consists of two component supporting faces adjoining one another in wedge-shape forming a front edge, and applied to each of the two component supporting faces is a supporting member together with a cutting layer which occupies the whole area. The cutting member which is wedge-shaped in its contours develops high drilling performances particularly in comparatively soft ground formations and is considerably cheaper than known wedge-shaped cutting members and renders possible an extensive variability in the formation of the supporting members together with the cutting layers and their arrangement on the carrier member.

A method of forming a PDC drilling bit including the steps of imposing a side drilling direction on the bit, determining a total bit side force acting on the bit, computing a walk angle between the total side force and the side drilling direction, and modifying a configuration of cutters on the profile of the bit so as to change the walk angle to a desired angle. The step of determining a total side force includes the steps of determining a normal side force of the bit, computing a total cutter friction force, and combining the normal side force and the total cutter friction force so as to produce a total side force. The total cutter friction force is obtained by summing single cutter forces perpendicular to a direction of cut of the bit. The step of imposing a side drilling direction includes measuring a normal side force applied to the bit. The modification of the bit can be carried out by increasing or reducing the aggressiveness of the cutters facing outwardly on an outer surface of the bit or by replacing cutters on the bit with low friction pads.

The invention relates to abrasive tools such as a cutting tool for a mining machine. Located in a socket 18 of the tool is a cutting insert comprising an elongate pin 22 having a bottom conical end 24 located in the recess and a top control portion 26 to which is bonded a composite abrasive compact. The composite abrasive compact having an abrasive compact layer 34 bonded to a cemented carbide substrate 36. The socket 18 complements the shape of the elongate pin 22 and, in particular, the bottom conical end 24. This arrangement minimizes the occurrence of stress raisers.