Sintered diamond bits have the diamonds embedded directly into the metal tip of the bit. As the tip wears down, new diamonds come to the surface. Sintered diamond drill bits are often designed for deep drilling in stone, tiles or masonry, Sintered diamond drills are more expensive and because they are heavy duty, they drill more slowly, but they last longer. Sintered diamond bits can last 30 to 50 times longer than a bonded diamond bit, sometimes even longer. The life of any type of diamond drill depends upon the hardness, abrasiveness and thickness of the material being drilled and the specific drilling techniques used (drill speed, pressure and lubrication).