CRL PDT Series Metal Bond Diamond Drills use a special diamond and brass bond for maximum performance in glass. Metal bond drills offer the greatest life, 1000 to 2000 holes in 1/4" (6.4 mm) glass with proper maintenance and the use of a wet Sharpening Stone to expose fresh diamonds, of any type of diamond drill. PDT Series Diamond Drills use a special diamond and brass bond for maximum performance in glass drilling. These Italian made multi-layer drills cut faster and run cooler than any other drill on the market. They have a full 3/8" (10 mm) deep cutting surface filled with diamonds and bronze bond, which allows for long drill life, but also makes this style drill more fragile. They should always be used in true running machines on flat glass surfaces. CRL PDT Series Drills can be used in portable drill machines such as the CRL AMZ1, but are especially suited for production equipment such as double-opposed drilling machines from ADA®, Besana-Lovati® or Schiatti® to name a few. These diamond drills feature Belgian style mounting threads, also known as 1/2" (12.7 mm) gas thread, which is popular among all U.S. and European glass drilling machines.