These high-speed steel cutting tools are designed for use with the Sherline boring head. They have a 3/8″ (9.5mm) diameter shank. The cutting end (P/N 3061) is designed to work in a 1/4″ (6.4mm) minimum hole with a maximum depth of .600″ (15.2mm). P/N 3063 is designed to work in a 5/16″ (7.9mm) minimum hole with a maximum depth of 1.00″ (25mm). P/N 3064 is also 5/16″ minimum but has a longer 1.5″ reach. If desired, they can easily be ground down to work in a smaller hole. These tools can also be used in the round hole of the 3/8 tool post on a lathe for boring. The shank has a flat ground on one side that is for the set screw of the boring head to tighten against.