Spade-type boring bit having chamfered corner portions

摘要

The spade-type boring bit includes an elongate shank defining a central longitudinal axis and a blade portion joined to one end of the shank. The blade portion includes a pair of generally flat side segments extending laterally from the central longitudinal axis and having a respective forward cutting edge and a respective chamfered corner portion. Each chamfered corner portion includes a chamfered edge which extends both axially rearward and laterally outward from the respective forward cutting edge so as repeatedly cut the peripheral wall of the resulting hole as the spade bit is rotatably advanced through a workpiece. The spade bit therefore produces a high-quality hole having a smooth peripheral wall and relatively clean entry and exit points. In addition, the forward cutting edges of the spade bit can be aligned with each other along a centerline which passes through the central longitudinal axis of the elongate shaft so as to increase the efficiency with which the spade bit drills. The spade bit also includes a spur joined to and extending axially from the forward end of the blade portion. The spur can include spur cutting edges separated radially, angularly and, in some instances, longitudinally or axially from the forward cutting edge of the adjacent side segment to prevent accumulation of chip swarf between the spur cutting edge and the adjacent forward cutting edge.