CorePlus Diamond Dry Core Drill Bit Set 7 Piece. The CorePlus Diamond Dry Core Drill Bit delivers a smooth drilling experience. Its 8mm diamond segments feature a high concentration of premium-grade diamond in the bond, utilising leading edge diamond/metal bonding, metallurgy, for long-lasting core life. A ribbed core body, and V-groove segments, enable the fast clearing of debris, allowing for a continuous fast cutting action, while the aerated core design enhances cooling, and extends core life. 1/2in BSP threaded compatible with standard core drilling machines and accessories. Please Note: 22mm and 28mm have a 10mm Hex Shank and do not require an arbor accessory. This 7 piece CorePlus Diamond Dry Core Drill Bit Set is supplied in a sturdy aluminium storage case. 3 x Diamond Dry Core Drill Bits: 38, 52 and 117mm. 30.1 x 30.1 x 39.5 cm. CorePlus is a UK diamond-cutting and abrasives specialist for construction professionals.