The 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. Specifications: • Dia Metric: 9.5 • Dia Imperial: 3/8 • Dia2 Metric: 4.76 • Dia2 Imperial: 3/16 • Overall Length Metric: 85 • Type or Grade: TCT