The special sawtooth design of CRL Amazing Glazing Plated Diamond Drills reduces the contact area, allowing better grinding action and increased coolant penetration. They are perfect for use in portable tripod and cup style machines. Our most durable drill has been machined from solid steel. Use with DTC80 Diamond Tool Coolant and submerge in a retaining ring for best results. Although plated, these drills may be sharpened one time with a CRL Sharpening Stone after they are totally worn out to expose some of the remaining diamonds. This will extend their work life for a period of time.