UNS Thread (USA)
The UNS thread is an American thread type with special pitch. It includes special combinations of pitch and diameter that are not covered by any other thread type. The UNS thread is designed for special cases, and it is recommended to revert to standard thread types such as UNC, UNF, or UNEF where possible. Where a special case requires a pitch-diameter combination that cannot be found in the listed thread tables, the UNS thread can be used. Besides the USA and Canada, it is also used in Australia, Great Britain, and New Zealand.
The UNS thread, like the UNC, UNF, and UNEF threads, belongs to the Unified National Thread Series (UTS). It was designed by the American Society of Mechanical Engineers (ASME) and is overseen by the American National Standards Institute (ANSI). The corresponding standard is ANSI/ASME B1.1.
The UNS thread is an inch-based thread with a flank angle of 60°. The thread designation follows the same principles as the other UTS threads. For threads with an external diameter under 1/4", a fixed numerical value is assigned. Since this is linked to the external diameter, but the same external diameter is repeated in the UNS thread, the situation arises that several thread sizes are designated with the same number. The number of threads per inch also specified in the thread designation serves as a distinguishing feature, e.g., 10 – 36 UNS. For threads from 1/4" onwards, the external diameter is specified instead of the numbering, also followed by the pitch and the acronym UNS, e.g., 1/4" – 40 UNS.
In the thread table for the UNS thread, the external diameter and the pitch in threads per inch are listed. In the table below, we have additionally stated the external diameter as a decimal number and converted it into a metric value. The pitch has also been converted into mm. Additionally, the core hole diameter is listed in the UNS table, which you will need to cut a UNS thread yourself.