| 摘要 |
<p>A gun drill excellent in machining performance, remarkably increased in machining speed as compared with conventional ones, providing a high deep-hole machining efficiency, remarkably prolonged in the life of the cutting edge, and particularly for a small-diameter one, reduced in the frequency of filing for re-use. A machining head (3A) having, at its tip face (3a), a coolant discharge port (30) communicating with a coolant supply passage (12) is fitted to the end (1b) of a hollow shank part (1) having, in its outer surface, a chip discharge groove (11) of a V-shaped cross section along the longitudinal direction and having, therein, the coolant supply passage (12). The cutting edge part (32) of the machining head (3A) is formed of a sintered alloy (W). Guide pads (5A, 5B) in slidable contact with the inner periphery of a cut hole are formed of a dissimilar material higher in hardness than the sintered alloy (W).</p> |
