What’s The Difference Between UNF and UNJF

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    What’s UNF Thread?

    UNF thread is an American Unified National Fine thread, which is part of the Unified Thread Standard (UTS) used in the United States and Canada. The UTS defines a standardized system of threads (screw threads) for fasteners, such as bolts and nuts. The “UNF” designation stands for “Unified National Fine,” where “fine” indicates the thread has a smaller pitch compared to the Unified National Coarse (UNC) thread, which is the other main thread type in the UTS.

    UNF has 60° thread angle. We can see many of UNF threads on JIC, ORB and ORFS hydraulic fittings and adapters.

    What’s UNJF Thread?

    UNJF is an American fine aerospace thread. It belongs to the J-series of American thread standards as described in ASME B1.15. 

    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.

    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.

    The Difference Between UNF and UNJF?

     An internal UNJ thread will assemble to a standard UN external thread but the reverse is not the same due to the interference at the minor diameter. The UNJ external threads have a larger root radius than a standard thread pitch. This ultimately improves the tensile stress area of the fastener, making the threads stronger. Many aerospace applications use these types of threads because of the increased strength.

    Hydraxio is manufacturing and supplying stainless steel hydraulic fitting and adapters for wholesalers, distributors and brand manufacturers of hoses and fittings. Please contact us for more details.

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