GB1194157A - Improvements in or relating to Drills. - Google Patents

Abstract

1,194,157. Drills. RADIAL LIP DRILL CORP. 10 May, 1968 [11 May, 1967; 14 Feb., 1968], No. 22425/68. Heading B3C. A drill comprises cutting lips 34, 36, Fig. 3, formed by continuous curves which merge tangentially with the periphery 42, 43 of the drill, and also with the lines 40, 41, which form the point angle of a conventional drill. To construct each of the curves 34, 36, angle α is bisected, and point D lies on this line. Radius R is drawn from point A, and equals the length AB, and this radius crosses lines 42 and 43 at points C. A line drawn between points C intersects the bisectors at points D. Radius R1, which is equal to the length CD is drawn, from each point D, tangential with lines 41, 43, and 40, 42, to thus form cutting lips 34, 36. In a modification, the cutting lips are tangential to lines 40, 41 at points remote from points B. In a further modification, the curves are ellipsoidal. The rounded outer edge 25, Fig. 6, of the lips may be removed to form flats 29. The drill may be a spade drill, Figs. 7, 8, with a carbide or steel tip, and may have cutting clearances 70. The drill 80, Fig. 15, may have first, second, and third relief 90, 92, 95, or four reliefs may be provided.