Trend CB12-316TC 3/16 drill diameter x 1/2 counterboreTCT Counterbore SetsThe CB counterbores are extensively used for recessing bolt and screw heads. Supplied with a HSS slow spiral drill bit. Fully adjustable, a hex key is supplied. TCT version is used for plywood, particle boards and plastics (abrasive). Use a drilling speeds only. Not suitable for ferrous and non-ferrous metals. When setting-up, ensure flutes of drill are aligned with flute of counterbore. For replacement Twist Drills, use slow spiral type e.g 501/532 to 501/012.Specification-D=1/2 inchD=12.7 mmD2=3/16 inchD2=4.76 mm