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The Complete Handbook of Drill & Screwdriver Bits
Professional Selection, Application, and Maintenance for Contractors, Shops, and Serious Users
by Alumigogo Books
Chapter 1: Understanding Drill & Screwdriver Bits
A drill bit is a cutting tool designed to bore holes into solid material by rotating at high speed. A screwdriver bit is a tool designed to drive or remove fasteners—typically screws or bolts—by transmitting rotational force. Both are small, replaceable, and so familiar that their design is rarely questioned. Yet the geometry, material composition, heat treatment, and fit of these tools determine whether a job is completed efficiently or turns into wasted time, broken equipment, and frustration.
Understanding how bits work is the foundation for choosing the right one, using it correctly, and recognizing when it needs replacement. This chapter explains the mechanics, design choices, and real-world consequences that distinguish a suitable bit from a poor one.
What Bits Actually Do
A drill bit removes material by cutting. As it rotates, the cutting edges—typically two flutes or lips on a twist bit—engage the surface of the workpiece and slice away small chips of material. The spiral flutes around the bit's body carry those chips away from the hole and toward the surface, preventing accumulation that would slow the cut, generate excessive heat, or jam the bit.
This sounds simple, but the success of that process depends on precise control of several variables. The angle of the cutting edge, called the lip angle or point angle, determines how aggressively the bit cuts and how much force is required. The spacing and angle of the flutes control chip evacuation and tool rigidity. The material