Concord Blades HEX500-2 Core Bit Adapter with 1-1/4-7 Thread to 1/2" Shank for Core Bits Shank Size 1/2 Inch (M) Thread Size 1-14"-7mm For use on a Hand Held Drill Converts 1-1/4"-7(M) thread for use in a normal 1/2" shank