Annular cutters, also called hole saws, are hollow drill bits that cut only around the periphery of a hole. They reduce the torque and horsepower requirements for drilling because they remove less material than standard twist drill bits. Annular cutters produce accurate, burr-free holes without the need for pilot holes. Their shanks have two Weldon flats ground into the shank at a 90-degree angle, to provide grip. They are commonly used with magnetic-base drills.
Drill bits are made of durable cutter materials such as high-speed steel (HSS), carbide and cobalt. Some drill bits are uncoated or bright; others have a finish – either a surface treatment or a coating - to enhance the bit’s performance on specific material types or in certain applications.
Drill point styles vary based on application. They have different point angles and style of cutting edges. The most common conventional style has a 118-degree point angle and is a good compromise between performance and price across a wide range of materials. Each style offers specific performance characteristics in different materials and drilling applications. Tool flute types are helical (curved) or straight grooves cut or ground into the body of the drill bit to provide cutting edges, enable removal of chips (also called swarf), and to allow cutting fluid or coolant to reach the cutting edges.
Another feature to consider is the shank, the portion where the drill bit is held by a tool holder. The shank transfers the torque to the drill bit. Drill bit diameter is the measurement around the bit’s shank. Drill bit cutter sizes are described by various sizing standards such as inch (English), metric, wire gauge (80 to 1), and letter (A to Z). This reflects the size of the hole being drilled. Standards ensure that dimensions are the consistent across manufacturers.