In metal-cutting operations, hole machining constitutes a significant proportion of the work, and a wide variety of hole-making tools are employed. Generally, hole-making tools fall into two major categories: The first comprises tools used to create holes from solid material-such as twist drills, spade drills, center drills, and deep-hole drills; the second consists of tools used to further process existing holes-such as core drills, reamers, countersinks, and boring tools.
As the most commonly used tool in hole machining, the drill bit is widely utilized throughout the mechanical manufacturing industry. Its application is particularly extensive and critical in the machining of holes in components such as tube sheets for cooling systems and power generation equipment, as well as in steam generators. A drill bit features cutting edges located at its tip and flutes along its body designed to evacuate chips. During the cutting process, the cutting speed of the drill bit is highest at the outer periphery; it decreases progressively toward the center, reaching zero at the drill bit's axis of rotation.
