| 摘要 |
A precision twist drill including two helical teeth separated by flutes. The diameter is equal to the minimum diameter of the hole to be drilled +0.005 mm, the heel (3) has a width of 0.1-0.2 mm, the teeth have no foreside; the end is ground according to two angles with a central radiate pit (4); the cutting edges (1, 2) of the two pits (4) are symmetrical and all the drill surfaces are polished with an accuracy of under 0.1 micron Ra. |
