U-Tools Diamond Bits Tornado Model 139T Blue – D139T-B is a MEDIUM nail drill bit manufactured by U-Tool. This bit is part of U-Tools new line of diamond nail drill bits called Tornado. Tornado Diamond Nail Drill Bits are grooved which allows for efficient, quick, accurate, and versatile use for a drill bit. The advisory speed limit for these Tornado bits are 25,000 RPM for small sized bits and 12,000 RPM for large bits. The use of alcohol is recommended while using these bits for effective disinfection and cleaning of the area that is being worked on.