UNEF Thread (USA)
The UNEF thread is an American fine thread with a particularly small pitch. Unlike the metric standard threads, the American series of standard threads Unified Thread Standard (UTS) not only has two subdivisions into coarse and fine threads, but even three: the coarse thread UNC, the fine thread UNF, and the extra fine thread UNEF. The acronym UNEF stands for Unified National Extra Fine. The UNEF thread is used for special purposes, such as in particularly thin-walled components. However, due to its fine pitch, it is not suitable for all applications.
Like all UTS threads, the standard for the UNEF thread was designed by the American Society of Mechanical Engineers (ASME) and is monitored by the American National Standards Institute (ANSI). It is ANSI/ASME B1.1.
The UNEF thread is an inch-based thread. This means that not only are all dimensions given in inches instead of mm, but the pitch is also defined by the number of threads per inch. However, this value can easily be converted into a mm value. The flank angle, like all UTS threads and the metric ISO thread, is 60°.
The thread designation for the UNEF thread is composed of the external diameter in inches, the pitch in threads per inch, and the acronym UNEF. Similar to the other UTS threads, thread sizes under 1/4" external diameter are designated with a fixed number. However, this condition applies to only one size in the UNEF thread. Accordingly, the correct thread designation for the smallest UNEF thread is #12 - 32 UNEF. For all other entries in the thread table, the thread designation works as described above, e.g., 1/2" - 28 UNEF.
In the thread table for the UNEF thread, information on external diameter and pitch in threads per inch can be found. In the thread table for the UNEF thread below, we have converted these values into metric equivalents for you. Also indicated is the core hole diameter in mm. This value is essential for a correct pilot hole if you want to cut a UNEF internal thread. You can easily find taps and dies for the UNEF thread in our store by following the corresponding link in the table.