| 摘要 |
1,201,585. Core drills. BROWN BOVERI & CO. Ltd. 10 Jan., 1969 [12 Jan., 1968], No 1646/69. Heading B3C. A core drill comprises a hollow shaft 3, Figs. 1, 2, indexable hard metal or high-speed steel cutter blades 35-38, secured in recesses 15-18 by clamps 20, 25, and guides 9 which co-operate with a guide bush 5. The latter has a sharp ridge or milling teeth on its under side 6, so that when rotated it digs into and is anchored to the workpiece 7. Lubricant under pressure is supplied to the cutters through shaft 3, an annular passage 13, and thence to oil return passages 27-30. Each cutter blade has three cutting edges 40, Fig. 3, which are radially stepped over the area to be drilled. In a modification, oil under pressure passes through a central passage, Fig. 6, and also through two further passages 52, 53 at a higher pressure, the oil in the latter passages passing through ducts 55 to arcuate pockets 57 in the drill head. |
