| 摘要 |
A metal cutting drill (10) with replaceable cutting inserts and a length to diameter ratio of four to one or more. Two cutting inserts (30, 31) are positioned in exactly opposed diametric positions, and engage the workpiece in a susbtantially identical manner to precisely balance the radial forces resulting from drill axially advancing through a workpiece. Though the use of dual cutting inserts (30, 31), the drill cuts the full circumference of a bore with each one-half revolution and therefore achieves a faster axial feed rate. By virtue of the inserts being triangular, the curved corners (37) on the cutting edges (45) of the two inserts (30, 31) may be positioned relatively close together and yet sufficient space is left between the inserts to enable the drill shank between the inserts to be relatively thick and strong even at increased length to diameter ratios. Through the provision of a length to diameter ratio greater than four to one, the bores which the drill is able to produce are substantially deeper at any given diameter than those achievable by prior art indexable drills. <IMAGE> |
