04-13-2013, 12:28 PM
(04-12-2013, 10:16 PM)wrustle Wrote: A "UNJ " is a jam thread.
We make some brass fittings for an aerospace customer with a 3/8-24 UNJ external thread. Once the fitting is installed, it will not vibrate loose. The root geometry on the thread is such that it creates an interference fit with the mating thread.
Best Regards,
Russ
I probably should add that the above statement is true if in fact you are screwing a jam thread into a standard thread it will be virtually an interference fit due to the increased radius size of the root geometry.
However, if the external jam thread is installed in an internal jam thread dia. the resulting fit makes for an extremely strong thread, again due to the difference in the root geometry of the external thread. For tapping a hole to use a "jam" thread the minor diameter must be increased to accommodate the larger radius of the fastener.
Clear as mud? I thought so......
http://www.amtektool.com/NATool-Tap-EnginData6.pdf