- Titanium Nitride coated for superior performance - Manufactured to exacting specification from long lasting tool steel - For cutting internal threads of nuts and holes - Includes recommended drill size - Taps and Dies are sized with two numbers. The first number signifies the screw or bolt diameter. - NC (USS) National Coarse General Purpose threading used on appliances and machines. - Thread types are: NC (USS) National Coarse General Purpose threading used on appliances and machines NF (SAE) National Fine Used for automotive parts requiring extreme pressures NPT National Pipe Taper For threading of pipes both eternal and external. - WARNING: Always wear eye protection