DIAMOND PRODUCTS Wet Stone Bit
These are the bits required for that large diameter and out of the ordinary hole. .125″ Thick segments, 5/8-11″ thread and a drill depth of 6″ These bits will do the trick. Available in all sizes but shown in the following Internet Order sizes only. All sizes have 5/8-11″ threads to fit a variable speed grinder with approximate 2,000 to 500 RPM speeds.