WIDIA - Полный каталог инструмента - 2017
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Technical Information
Inch Screw Thread with UNJ Prole
A thread system is available for aerospace and other applications where high fatigue strength is
required. The UNJ thread form is defined by ASME B1.15 and is similar to Military Specification
MIL-S-8879. Screw thread assemblies consist of external and internal threads. In order to
minimise the stress on the external UNJ thread, a controlled root radius is required that
is equal to 0.15011P to 0.18042P, where P is the thread pitch. Internal UNJ threads are
not required to have a radius at either the major or minor diameters.
Nut:
UNx/UNJx
Screw:
UNx
UNJx
UNx:
R0.14434P-0.125P
Because external UNJ threads must be produced with a defined
root radius, standard UN tooling may not be used. However, internal
UNF threads may be produced with ground thread UN taps sized to
produce the proper class of fit. The tap does not need to be marked
with a letter J. Attention must be paid to the tap drill since the minor
diameter has to be specified so as to provide clearance with the root
radius on the external thread.
For UNJ thread specifications, the reader is referred to ASME B1.15.
Please note this standard includes Class 3 and Class 2 UNJ screw
threads. However, only Class 3 UNJ threads meet the requirements
of Military Specification MIL-S-8879. For Unified Inch (UN) thread
specifications, refer to ASME B1.1.
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