Thread type: UNF Unified National Fine Thread Series ANSI B1.1

American fine thread

The thread in the UNF thread table is an American thread standard and is part of the Unified Thread Standard (UTS). The UNF thread is a fine thread and, together with the associated coarse thread UNC, is the standard for screws and nuts in the USA and Canada. The UNF thread is also used in other countries such as Australia, Great Britain and Japan. In Germany, the UNF thread table is particularly relevant in the aviation sector, as many screw connections on Boeing or Airbus commercial aircraft are designed as UNF threads. The standard for the thread, which is also shown in the UNF thread table, is specified and monitored by the American National Standards Institute (ANSI). The table shown for the UNF thread is specifically the ANSI B1.1 standard.

As can be seen from the UNF thread table, the UNF thread as a fine thread has a smaller pitch than a coarse thread. This creates a better self-locking effect, which makes the UNF thread ideal for environments in which frequent vibrations and shocks occur. It has a flank angle of 60° and is an imperial thread, so all dimensions are given in inches.

In the UNF thread table you will find all the information you need to work with this thread. The thread designation is made up of the abbreviation UNF, the outside diameter in inches and the number of threads per inch. However, this only applies from a thread size of 0.250 inch outside diameter. In the UNF thread table, you can clearly see that the ten thread sizes below this value are assigned fixed numbers. These are defined in the ANSI B1.1 standard and are supplemented by the English abbreviation "No." for number.

In our table for the UNF thread, we have also included the corresponding value in mm in addition to the outer diameter in inches. In this way, you can easily read both values and do not have to convert them first. We have also supplemented the indication of threads per inch with the pitch in mm, which is common for metric threads. This makes the UNF thread table a valuable tool for you even if you prefer to work with metric values.

 Major Diameter inchMajor Diameter mmTPIPitch P in mm
UNF No. 0 - 800,0601,524800,317
UNF No. 1 - 720,0731,854720,353
UNF No. 2 - 640,0682,184640,397
UNF No. 3 - 560,0992,515560,453
UNF No. 4 - 480,1122,845480,529
UNF No. 5 - 440,1253,175440,577
UNF No. 6 - 400,1383,505400,635
UNF No. 8 - 360,1644,166360,705
UNF No. 10 - 320,1904,826320,794
UNF No. 12 - 280,2165,486280,907
UNF 1/4" - 280,2506,350280,907
UNF 5/16" - 240,3137,938241,058
UNF 3/8" - 240,3759,525241,058
UNF 7/16" - 200,43811,112201,270
UNF 1/2" - 200,50012,700201,270
UNF 9/16" - 180,56314,288181,411
UNF 5/8" - 180,62515,875181,411
UNF 3/4" - 160,75019,050161,587
UNF 7/8" - 140,87522,225141,814
UNF 1" - 121,00025,400122,117
UNF 1 1/8" - 121,12528,575122,117
UNF 1 1/4" - 121,25031,750122,117
UNF 1 3/8" - 121,37534,925122,117
UNF 1 1/2" - 121,50038,100122,117
Cross section of a UNF thread