| 摘要 |
1,144,035. Twist drills. LOCKHEED AIRCRAFT CORP. 1 May, 1967 [2 May, 1966], No. 20130/67. Heading B3C. A twist drill comprises cutting lips each of which has a primary section 5, Figs. 1 and 5, and a secondary section 6. The chisel edged angle of section 5 lies between 115 and 125 degrees, and that of section 6 between 125 and 135 degrees, and the positive rake angles of sections 5 and 6 lie between 12 and 16 degrees, and 4 and 6 degrees respectively. The width of the chisel edge is approximately 10% of the drill diameter, and the width of the facets at the margin of the rake angles is 10 to 15% of the drill diameter. |
