Diamond twist drills are used to enlarge holes. Notable usage is in enlarging holes in beads, increasing holes in pearls. Shovel shaped pointed drill bits are used to drill hard materials. Diamond drill bits are hollow. Water is used as a lubricant and coolant. This coolant flows up inside and the inner core as they are hollow. This allows the drill to cool and remove the debris. The lubricants also help inprolonging the life of the drill bits and shattering or cracking of the material being drilled. For more details please visit at our website https://goo.gl/DBgWkc.