DRILL FOR MAKING A FLAT-BOTTOMED HOLE

摘要

The present invention is directed to a helical drill configuration that allows substantially flat bottomed holes to be machined. At the cutting end of the body member, there are at least two cutting edges (35) that are symmetrically oriented on apposing sides of the rotational axis of the drill. In an embodiment of the invention, first (36) and second (35) cutting edge portions form a continuous surface which provides strength and tool stability. The height of the second portions (35) of each of the cutting edges remains relatively consistent along the horizontal formation of a generally flat bottom hole. In the embodiment, a center point is defined by two sloped peak surfaces (45). A central straight chisel edge (41) is formed by the intersection of the two sloped peak surfaces (45). The first cutting edge section (36) extends from the chisel edge to the second cutting edge section (35). The first cutting edge section for both cutting edges is formed by symmetrically thinning the two peak surfaces (45). In the invention, stress at the center portion of the helical cutting tool is limited by the chisel edge (41) and first sections (36) of the cutting edge near the center portion having a balanced geometry. The balanced geometry of the helical drill also prevents the drill from wobbling and creating deviations in the hole being formed.