Countersinking, Counterboring, and Spotfacing
Countersinking, counterboring, and spotfacing operations can be carried out on drilling machines and usually follow drilling operations. This article discusses five common types of countersinking tools or countersinks, namely, machine, three-flute, single-flute, insert-type, and interchangeable countersinks. It provides a short description of the two types of spotfacing tools: back and double-end spotfacers and automatic back spotfacers. The article describes different types of counterboring tools, including interchangeable-pilot, integral-pilot, and interchangeable-cutter counterbores. It tabulates the nominal speeds and feeds for counterboring and spotfacing of carbon and low-alloy steels with high-speed steel and carbide tools.