For the carbide family of these tools, the three-flute represents the ideal "general purpose" countersink. They have enough chip clearance in the three-flute design for a variety of ferrous and non-ferrous materials, while providing enough strength with the radial relief design to attack hardened materials up to 40Rc. Solid carbide tools offer long tool life and faster cutting speeds than other substrates, but are more brittle and must be used with rigid toolholding systems. Titanium aluminum nitride coatings become self-lubricating when used at very high speeds, making them ideal for cutting without coolant ("dry machining"). 60 degree angle.