6 Grobet Twist Drill Bits Great for Metalsmiths, Metal Working & Drilling. This is a new set of 6 twist drill bits Great for drilling metal, plastic, wood and stone. Long time jewelers favorite. Made in Switzerland with Swiss quality and workmanship. These have an ISO of 014. Each shank measures 3/32" (2.3 mm). Each bit is a size 3 and measures approximately 1.4 mm in diameter.