摘要 |
A drill two spiral cutting edges(10) has center symmetrical edge courses from drill center and with greater curvature in central drill section. The drill comprises a pair of cutting edges extending from the center of rotation of the drills symmetrically w.r.t. the center and curved outwardly away from the direction of rotation of the drill. There is a greater curvature in the center portion than in the outer periphery portion of the drill when seen in a bottom view. The cutting edge is formed, close to its starting end, with a rake face having a rake angle close to zero to enable the starting end portion of the edge to cut a workpiece with greater ease.
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