The present invention is an improvement in the cutting tooth used in a rotating drilling bit wherein the cutting tooth incorporates a synthetic triangularly shaped prismatic diamond element. The polycrystalline diamond element is substantially exposed above the bit face of the bit and is supported and retained on the bit face by disposition within a tooth of matrix material integrally formed with the bit face. The tooth is particularly characterized by having a trailing support in the shape of a tapered teardrop with a leading face on the trailing support that is at least in part adjacent and contiguous to the trailing face of the diamond cutting element and is congruous at the plane of contact with the diamond cutting element and tapers thereafter to a point on the bit face to minimize the amount of matrix material in the tooth which must to be removed by wearing before a useful cutting surface of the polycrystalline diamond element can be exposed.

An earth boring bit utilizing thermally stable polycrystalline diamond material having a row of closely spaced sharp cutting elements, following by a row of widely spaced, blunt or rounded cutting elements, each cutting element extending from a supporting matrix a predetermined amount to allow the sharp cutting elements to form small relief kerfs in a geological formation, after which the blunt or rounded cutting elements dislodge material between the kerfs. Additionally, cylindrical cutting elements are positioned near the gage or outermost portion of the matrix to enhance gage bore cutting.

Teeth disposed on the bit face of a rotating bit are, angularly oriented on the sloping surface of the bit face such that a vertical loading force which is applied to each tooth vectorially sums with a wedging force exerted by the rock formation on each tooth to create a resultant force applied to the diamond cutting element included within the tooth. The angular orientation of the tooth is chosen such that the resultant force is applied to the diamond cutting element in a direction which minimizes shear stress on the element. For example, in the case where the diamond cutting element is an equilateral triangular prismatic element tangentially set on the bit face with one apical edge defined by two adjacent triangular sides outermost on the tooth, the orientation or inclination of the tooth with respect to the vertical loading force and wedge force is such that the resulting force lies near or on the bisector of the dihedral angle formed by the apical edge. Similarly, the diamond cutting element is rearwardly raked in the longitudinal direction, generally parallel to the tangential motion during normal drilling as defined by the rotation of the bit, such that the vectorial sum of the vertical loading force in a reactive cutting force applies a resultant force on the diamond cutting element in a direction which minimizes shear stress, namely, in the example in a direction approximately perpendicular to one of the end faces of the triangular prismatic diamond cutting element.

Tool for drilling bore holes and earth formations in which a bit body matrix, including tungsten carbide, has a plurality of carriers secured thereto, to each of which a cutting element is secured by soldering, after the body matrix has been produced, to avoid subjecting the diamond material embodied in the cutting element to the high temperatures required to produce the matrix body, which would have deleterious effects on the diamond. Each carrier has great rigidity and is provided with a plane surface confronted by the plane back surface of the cutting element to provide a desired narrow solder gap between the cutting element and carrier of uniform width, into which the solder is deposited to adhere the cutting element and carrier together, with the load being transmitted directly from the cutter element to the rigid carrier.

To allow the bit to drill in formations that behave plastically, while also protecting the bit against overloading when entering a relatively soft formation, ridge-shaped elements are provided having the ridges within the rotation alloy symmetric surface defined by the scraping edges of the scraping means (natural or artificial diamonds). The flanks of the elements are positioned at an acute angle to the said surface.