Busch 4203 4 Groove Carbide Twist Drills on 3/32" Shanks .70mm-1.60mm - Kit of 10

The 4 groove design of these special 3/32" mounted carbide twist drills works best with softer materials, so these carbide drills are recommended for cutting coral and pearls. These drills will last the longest when used in a drill press, as like any drill, breakage will occur with excess leverage or canting. If using by free-hand, the recommended speed is 5,000 to 9000 rpm, and the use of a starting guide hole will help. For use in a press, the recommended speed is from 8,000 to 14,000 rpm. Not for use with glass, ceramics and gem stones. 4 Groove-Recommended for softer materials like Coral and Pearls-Outstanding Service Life Kit of 10 includes: B128.707  0.70mm B128.708  0.80mm B128.709  0.90mm B128.710  1.00mm B128.711  1.10mm B128.712  1.20mm B128.713  1.30mm B128.714  1.40mm B128.715  1.50mm B128.716  1.60mm