A NEW DIAMOND CUTTING STRUCTURE, COMMONLY CALLED A DIAMOND ENHANCED INSERT, HAS BEEN DEVELOPED FOR ROTARY PERCUSSION DRILLING. SEVERAL YEARS WERE DEVOTED TO THE DEVELOPMENT AND TESTING OF THIS ADVANCEMENT. THE RESULT IS A MULTI-LAYERED DIAMOND COATING BONDED TO A TUNGSTEN CARBIDE SUBSTRATE. THE MULTI-LAYERED COATING GREATLY IMPROVES IMPACT RESISTANCE. DIAMOND ENHANCED INSERTS HAVE SEVERAL ADVANTAGES OVER CARBIDE. THEY INCREASE BIT LIFE, PROVIDE BETTER HOLE QUALITY, REDUCE DOWN TIME, AND DECREASE DRILLING COSTS.