Unified Thread Standard

The Unified Thread Standard is a standard for threads, which is common in the United States and Canada.

Here, the outer diameter of a screw in inches and the thread pitch in turns per inch is specified (instead of millimeters per revolution ).

For diameters less than ¼ inch of diameter is given by a function defined in the standard number from the following table. The name (in the first column of the table) is known in English as "number" ( number), so for example "number zero" ( number zero) spoken.

For all diameters from ¼ inch of the value in inches or fractions of inches is specified. Usual, the gradations

When the slope is made between the control thread UNC (unified coarse) and fine threads UNF (unified fine) and UNEF (unified extra fine ). In addition, there are special cases for the UNR and the U.S. (unified special), which is used for example in a microphone stand for use.

For example, the term 1/2-13 UNC as much as 0.5 inches outer diameter, pitch 13 turns per inch, standard thread.

All screw on western commercial aircraft (Boeing, Airbus, ... ) are implemented as UNF thread.