The external thread size of a Schrader valve is 0.305 inches outer diameter by 32 threads per inch (TPI), and it has a thread root diameter of 0.302 inches outer diameter. The valve also has an internal thread of 0.209 inches outer diameter by 36 TPI. If no taps and dies of 0.305 inches are available, then 0.302 inch taps and dies are suitable replacements.
The Schrader valve, also known as the American valve, is a pneumatic tire valve found on most motor vehicles around the world. It is also used in refrigeration units and SCUBA diving and aircraft equipment. It is also sometimes used by plumbers when pressure-testing pipe systems.