MARTIN YALE Hollo Drill Bits These superior grade bits, standard or ordered with the exclusive Diamonizing Process, provide clean, smooth drilling. Hollow drill bits resist chipping, twisting and clogging. Chromium, vanadium and molybdenum combine to create long-lasting and depend- able tools. Seven styles are available in vertical capacities from 1" to 2/2" and 12 hole sizes from /8" to /2" diameter. The optical Finishing EquipmentDiamonizing Process impregnates the steel with tungsten carbide to make the bit 90% the hardness of diamond. The resulting bit lasts up to four times as long.