Topology of Spade Drills for Wood Drilling Operations, Part 1: Spade Drill Point Geometry Definition

Spade bits, widely and routinely used in the construction industry, have not received any attention in the technical literature, yet there is a pressing need to improve the performance of these bits whose basic design has not changed for decades. To facilitate such improvements, a thorough understanding of the geometric, manufacturing, and cutting mechanics aspects of these tools is necessary. In this two-part paper, the point geometry and manufacturing issues will be discussed. To fundamentally understand the spade drill bit’s behavior, a complete mathematical model of its principal topological elements will be established. In conjunction with this model, the corresponding analytical formulations of the geometry and kinematics of the appropriate manufacturing procedures will also be formulated. In unison, these models will lay the foundation for a methodology and a software package for a detailed geometric analysis of all relevant cutting angle distributions and edge profiles of the spade bit. This will facilitate, at a later point, new point developments rooted in rigorous analytical models.