Drill bit

A drill bit is a cutting tool used with a drill to remove material and create holes, typically with a circular cross-section. Drill bits are available in various sizes and shapes, designed to produce different types of holes in a wide range of materials. To function, drill bits are usually mounted in a drill, which provides the rotational force needed to cut into the workpiece. The drill will grasp the upper end of a bit called the shank in the chuck.

Drills come in standardized drill bit sizes. A comprehensive drill bit and tap size chart lists metric and imperial sized drills alongside the required screw tap sizes. There are also certain specialized drill bits that can create holes with a non-circular cross-section.

Drill geometry has several characteristics:

The majority of drill bits intended for consumer use are designed with straight shanks. For heavy duty drilling in industry, bits with tapered shanks are sometimes used. Other types of shank used include hex-shaped, and various proprietary quick release systems.

The diameter-to-length ratio of the drill bit is usually between 1:1 and 1:10. Much higher ratios are possible (e.g., "aircraft-length" twist bits, pressured-oil gun drill bits, etc.), but the higher the ratio, the greater the technical challenge of producing good work.

The best geometry to use depends upon the properties of the material being drilled. The following table lists geometries recommended for some commonly drilled materials.

Many different materials are used for or on drill bits, depending on the required application. Many hard materials, such as carbides, are much more brittle than steel, and are far more subject to breaking, particularly if the drill is not held at a very constant angle to the workpiece; e.g., when hand-held.

General-purpose drill bits can be used in wood, metal, plastic, and most other materials.