DiamondSure brand Pro-Sintered Diamond Drill Bits are also know as Sintered Diamond Core Drill Bits or Sintered Diamond Hole Saws. These are professional quality, heavy-duty diamond drill bits designed for use on ceramic tile, porcelain tile, limestone, sandstone, marble, granite, quartz and other stone, plus bricks, masonry, concrete block, and concrete. Water must be used for lubrication. Sintered diamond drill bits have the diamonds embedded into the metal of the drill bit tip rather than merely "bonded" to the tip as with bonded diamond drill bits. As the tip wears down on a sintered diamond drill bit, new diamonds come to the surface. Sintered diamond drill bits are heavy-duty bits designed for long life. Generally, sintered bits will have a long life of 20 to 30 or more times the life of a bonded diamond drill bit, if used properly. The heavy-duty design provides long life when drilling in very hard materials such as porcelain tile, granite and hard stones. There are some disadvantages. Sintered bits are more expensive than bonded diamond bits and the thick heavy-duty tip causes them to drill more slowly than thin-wall bonded diamond drill bits. However, for highly repetitive drilling in hard mateirals, the higher cost of the Sintered Diamond Drill Bits is well worth it because of the much longer drill bit life. Sintered bits are also necessary for drilling beyond about 1/2" deep as the heavy-duty design can withstand the severe heat of deeper drilling in hard materials.