GB838570A - Improvements in and relating to drill bits and drilling - Google Patents

Abstract

838,570. Boring earth &c. DRILLING & SERVICE Inc. Feb. 24, 1958 [March 8, 1957], No. 5865/58. Class 85 An earth boring drill bit comprises a hollow threaded shank 11 (Fig. 1) and an integral enlarged body portion 12 which is generally triangular in shape and has three cylindrical cutting faces 16 joined by hands 14. The three cutting faces curve inwards to form an end cutting face 20 at the centre of which is a conical recess 19. The whole of the cutting face is set with diamond abrading elements 42. A duct 22 leads from the hollow shank to the end cutting face and feeds drilling fluid to four primary passages 26, 26, 32 and 34. Each of the passages 26, 26 and 34 leads to one of the cylindrical surfaces 16 and has lateral passages 28, 30, 36 and 38 leading off it to distribute the drilling fluid over the external and internal cutting faces and lands. The fourth primary passage 32 directs additional fluid into the conical recess. The cross-sectional area of the primary passages is reduced after each lateral passage leads off by an amount approximately equal to the crosssectional area of the lateral passage. Material abraded in the conical recess is discharged through the opening 40. In a modification (Fig. 7) the drill is converted to a core bit by modifying the conical recess 19 to a parallel sided axial holepassing through the bit and lined with diamond abrading elements 72. Drilling fluid grooves 62, 64, 66 and 68 are provided.