Abstract: A method of thermally treating a preform element, of the kind having a facing table of polycrystalline diamond bonded to a substrate of cemented tungsten carbide, comprises the steps of:

Abstract: A cutting element for a rotary drag-type drill bit comprises a body of polycrystalline diamond incorporating a binder-catalyst selected from iron group elements, such as iron, cobalt and nickel, or alloys thereof. The body of polycrystalline diamond is unsupported by an integral substrate. The cutting element may be mounted directly on the body of the drill bit, or may be brazed to a substrate of a different, less hard material which is in turn mounted on the drill bit.

Abstract: A cutting element for a rotary drill bit includes at least one insert of polycrystalline diamond of a kind incorporating a carbonate as a sintering binder-catalyst. The insert is mounted by being at least partly surrounded by a support body of conventional polycrystalline diamond of a kind incorporating a sintering binder-catalyst selected from cobalt and other iron group elements or alloys thereof. The insert and support body may be integrally bonded to a substrate during manufacture. Either the insert or support body may be pre-sintered or sintered during formation of the cutting element.

Abstract: A preform cutting element, for a rotary drag-type drill bit, includes a facing table of polycrystalline diamond having a front face, a peripheral surface, and a rear surface bonded to the front surface of a tungsten carbide substrate. The facing table has at least one peripheral locking portion projecting rearwardly from the rear surface of the facing table into the substrate, the inner surface of the locking portion and the adjacent part of the substrate having interengaging formations whereby part of the substrate overlies at least one part of the locking portion. With this arrangement, forces acting on the facing table tending to lift it from the front surface of the substrate are resisted by the portion of the substrate which overlies the part of the locking portion.

Abstract: Formation engaging elements are moveably mounted onto a drill bit. Such elements may be used to protect other rigidly mounted formation engaging elements from impacts that occur during use of the drill bit, or they may be used to alter the aggressiveness of the drill bit when used in directional drilling operations.

Abstract: A preform element comprises a substrate having an outer peripheral surface and at least one end surface. At least a portion of the peripheral surface of the substrate has bonded thereto an inner surface of a peripherally extending facing layer of superhard material, such as polycrystalline diamond. The portion of the peripheral surface of the substrate and the inner surface of the peripheral facing layer are provided with inter-engaging formations, such as ribs and grooves, whereby the peripheral facing layer is keyed to the substrate.

Abstract: A preform element includes a facing table of superhard material, such as polycrystalline diamond, having a front face, a peripheral surface, and a rear surface bonded to the front surface of a substrate which is less hard than the superhard material. The front surface of the substrate is formed around its periphery with an annular rebate having an inner edge, a number of spaced recesses adjacent the inner edge of the rebate, and projections of superhard material integrally formed on the rear surface of the facing table extend into the rebate and recesses.

Abstract: A preform cutting element for a rotary drag-type drill bit comprises a front facing table of superhard material having a front surface, a peripheral surface, a rear surface bonded to a substrate of less hard material, and a cutting edge formed by at least part of the junction between the front surface and the peripheral surface. The front surface of the facing table is formed with a chip-breaking formation which is located adjacent the cutting edge and is shaped to deflect transversely of the front surface of the facing table cuttings which, in use, are removed by the cutting edge from the formation being drilled. The chip-breaking formation may comprise a peripheral groove or rebate, or an upstanding ridge or insert.

Abstract: A method of thermally treating a preform element, of the kind having a facing table of polycrystalline diamond bonded to a substrate of cemented tungsten carbide, is disclosed. The steps of the method are: (a) heating the element to a soaking temperature of about 600.degree. C., (b) maintaining the temperature of the element at that temperature for two to three hours, and (c) cooling the element to ambient temperature. These steps are preferably then followed by a flash heating cycle. These steps are: (d) heating the element to a temperature in the range of 750-850.degree. C., (e) maintaining the temperature of the element at that temperature for about four seconds, and (f) cooling the element to ambient temperature. This thermal treatment relieves residual stresses in the element in order to reduce the risk of cracking or delamination of the element in use.

Abstract: A preform cutting element for a drag-type rotary drill bit includes a facing table of polycrystalline diamond bonded to a less hard substrate, such as cemented tungsten carbide. The element is formed by first forming a solid substrate, and then applying an electron beam, laser, or other intense heating source to adjacent areas of the front surface of the substrate to melt the surface and form an array of holes or holes therein. A layer of polycrystalline diamond particles is applied to the substrate so that such particles fill the holes or holes, and the diamond layer and substrate are then subjected to pressure and temperature in a high pressure, high temperature press to bond the superhard layer to the substrate. The engagement of parts of the diamond table in the holes or holes in the substrate provides a mechanical interlock to improve the strength of the bond between the table and substrate.