Core Drill Shaft Adapter 1 1/4"-7 Female To Male 5/8”-11 Adapter For Core Drill Bits - 3 PackCore Drill Shaft Adapter 1 1 4" 7 Female Thread to 5 8 11 Male Adapter For Core Drill Motors 3 Pack Shaft Adapter Attachment for Diamond Core Drilling 1 1 4" 7 Female Thread to 5 8" 11 Male Thread for Use with Diamond Core Bit that have a 5 8" 11 Female Thread. Core Drill Bit Adapter Reducer For Wet or Dry Drilling Common Use: Core Bits under 2" Diameter & Dry Drilling Core Bits Quality Steel Heat Treatment For Thread Durability & Strength 5 8" 11(M)