Design: Excellent chip removal and ideal chip flow due to spiral grooves. Easy to resharpen. The countersink is secured against twisting in the holder. Note: Flute countersinks are also available in HSS with optional TiN coating, as well as with soldered carbide cutting edges and with ISO indexable inserts type "T" upon request. Application: For countersinking screws according to DIN or for creating stepped holes or recesses outside of the standard through the appropriate combination of countersink and pin.