Special jaws made of air hardening tool steel (A-2) 58 - 63 Rockwell "C" with braze carbide inserts. Chuck Grips 1/8 inch shank carbide Micro frills, RTW grinds flutes to diameters down to .002 inches Drills are for circuit board drilling. Stack 3 boards drill 3 holes per second at 100.000RPM