UNF Thread size chart

UNF threads, unlike UNC threads, have a finer pitch. These types of threads are used in applications which require high tensile strength and in applications where the threaded parts are relatively thin. Some similarities can be found between UNC and UNF threads. Both UNC and UNF threads in male and female versions are parallel to each other. Also, the flank angles of both UNC and UNF threads are 60 degrees. The typical designation of a UNF thread is ½” x 20.  The standard of UNF threads is managed by the ANSI/ASME B1.1 Unified National Thread.

The UNF thread has a smaller space occupation size and better self-locking performance when compared to a UNC thread. A number of different fine thread types can be found to make a series of fine threads - MF/UNF/UNRF. these fine threads are not generally used in applications which require a large stress. Usually, fine threads are used in applications like positioning and fixing adjustments, and similar instances where high fastener strength is required. Also, fine threads are used in applications where fine adjustments are done. for instance, these threads are used in tools like micrometers and to fix lenses in various optical instruments, and battery covers of metal-shelled flashlights.

Although with its specified advantages, has its disadvantages too. As the fine thread is comparatively smaller in height and size, it can be prone to displacement and disorder very easily. Also, it should be regularly cleaned up as the burr is important during assembly. moreover, it can be difficult to remove the threads in case of any emergency, due to their small size.

UNF threads have a smaller pitch and consist of more teeth screwed in the same thread length. This feature is important as it can prevent fluid leakage, and is made use of in applications where sealing is needed. As UNF threads have a smaller cross-section size of each tooth, with a large number of teeth, they are generally replaced with UNC threads for applications that require bearing a large tensile force and impact force. However, compared to the UNF threads, UNC threads have a batter interchangeability and higher measure of strength, while also possessing greater tolerances and thereby handling manufacturing in a better way than UNF threads.

However, based on their different characteristics, both UNC and UNF threads have different uses and are applied in a wide range of applications.