Thread type: UNJF - Unified fine thread for aerospace acc. to DIN-ISO 3161 and ASME B1.15

The thread shown in the UNJF thread table is the American fine aerospace thread. It belongs to the J-series of American thread standards as described in ASME B1.15. The aerospace threads of the J-series, of which the thread in the UNJF thread table is only one, are based on the corresponding UN threads with slight modifications. The UNJF thread shown in the thread table is also standardized according to DIN-ISO 3161. The specifications shown in the UNJF thread table correspond to those in the UNF table.

In order to adapt the thread of the UNJF thread table to the enormous requirements in the aerospace sector, a number of changes have been made. The entire field of application not only places particularly high demands on the service life and load-bearing capacity of the threads. The materials into which threads have to be cut are also characterized by high resistance, which often goes hand in hand with difficult machinability. The UNJF thread table must take these circumstances into account. On the one hand, this is achieved through an adapted thread profile, for which the thread tips are rounded, which prevents cracking. In addition, the tolerances in the UNJF thread table are much tighter in order to ensure a wide overlap between the external and internal threads. Furthermore, the thread core is flattened in accordance with the UNJF thread table, which results in a larger radius for the external thread and therefore a higher fatigue strength.

The UNJF thread has a flank angle of 60°. The UNJF thread table shows selected thread sizes whose dimensions correspond to the UNF templates. The thread designation in the UNJF thread table is made up of the abbreviation UNJF and the outside diameter in inches. Exceptions to this rule are the first two entries in the UNJF thread table. These two sizes are designated with the fixed numbers No. 8 and No. 10 respectively. The values in the UNJF thread table are given in inches. For ease of use, you will find conversions of outside diameter and core hole diameter in mm in our UNJF thread table. The pitch is also given as a metric value in addition to the usual representation for inch threads in threads per inch.

The UNJF thread is a modification ot the unified fine thread acc. to ANSI B1.1.

Through a greater flattening of the thread core, a larger radius in the external thread is possible.
This results a lower stress concentration, which allows a higher fatigue strength.

in Inch
in mm
core hole-Ø in mmThreads per InchPitch P
in mm
UNJF No. 80,1644,1663,55360,705
UNJF No. 100,194,8264,15320,794
UNJF 1/4''1/46,3505,60280,907
UNJF 5/16''5/167,9407,00241,058
UNJF 3/8''3/89,5308,60241,058
UNJF 7/16''7/1611,11010,00201,270
UNJF 1/2''1/212,70011,50201,270
UNJF 9/16''9/1614,30012,30181,411
Cross section of a UNJF thread