Counterbores are cutting tools that have a pilot to guide them into a previously drilled hole. They are used to form a recess or pocket for a socket head capscrew. These tools are of a solid high speed steel construction. High speed steel is a common general purpose material for cutting tools and is used to cut a variety of different materials.
Used to enlarge existing holes
One piece construction including the pilot
Round shank tools are cylindrical and should be held in a good quality tool holder in order to prevent the counterbore from slipping in high torque applications
High-speed steel is a common general purpose steel for cutting tools, is compatible with a variety of materials, and tends to be lower in price
Uncoated (bright) tools have no finish or coating. They are a good choice for general purpose applications.