UNC Thread (USA)
The UNC thread is the American coarse thread. In terms of use and prevalence, the UNC thread is the American equivalent of the metric ISO thread M. It is used worldwide in many countries, including the USA and Canada, as well as Australia, Japan, and India. In its country of origin, the UNC thread is the standard for fastening screws and nuts.
The abbreviation UNC stands for Unified National Coarse Series and identifies the thread as a coarse thread belonging to the Unified Thread Standard (UTS) family. All UTS threads are developed by the American Society of Mechanical Engineers (ASME) under supervision by the American National Standards Institute (ANSI). The UNC thread corresponds to the ANSI/ASME standard B1.1.
The UNC thread is an inch-based thread, so all UNC measurements are made in inches. The flank angle is 60°, as with many widely used thread types, such as the metric ISO thread. The pitch for the UNC thread is, as usual for inch-based threads, given in threads per inch. However, this value can easily be converted into a pitch in mm.
The thread designation consists of several components that vary depending on the thread size. Always indicated are the number of threads per inch and the abbreviation UNC. Preceding these two values, starting from an external diameter of 1/4", is the specification of the external diameter. All thread sizes with an external diameter of less than 1/4" are numbered – in this case, the additional specification of the diameter is omitted. Depending on the size, a correct designation for the UNC thread would be either #4 - 40 UNC or 7/16" - 14 UNC.
In the thread table for the UNC thread, the external diameter and the number of threads per inch are given. In the thread table for the UNC thread below, we have also converted these values into metric equivalents. Additionally, we have listed the correct core hole diameter in mm, which you will need if you want to cut a UNC thread yourself. For taps and dies in the corresponding sizes, please simply follow the links in the table!