A hole opener bit is a cutting tool for a general drill or drilling machine to cut circular holes. The basic principle of the drill bit
is that the edge rotation cuts workpiece and that debris is removed by the drilling groove.
Common bits are the twist bit, the flat bit, the center bit, the deep-hole bit and the casing bit. Although never do reamers and countersinks drill on solid materials, they are traditionally classified as the drill bits.
A hole opener bit
has a cutter rod with a tip, which is provided with two cutting blades on a principle plane. On a common second plane, the blades have a short central cutting edge, which forms a point-shaped center incut edge for the workpiece thereby aligning the drill bit.
Extending from the tip to the end, two chip removal grooves are arranged on the cutter rod, of which any cross section along lays the grooves diametrically opposite to each other on the pipe plane. The pipe plane extends 90° with the common edge plane formed by the two edges on both sides of the pipe, where the cutter bar reaches the maximum rigidity. The orientation of the second plane of the central cutting edge is approximately 90° with the principal rigid direction of the edge plane or the bottom of the cutter rod.