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unjf thread taps? 2
- Thread starter DUKEOACES
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To the best of my knowledge, there is no difference between a UNJF tap and a UNF tap. The UNJF internal thread has a larger minor diameter than the UNF, but the controlled root radius applies only to external threads.
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DukeoAces...
I worked many MIL acft and their weapons pylons... this is a very strange and potentially damaging action, in humble opinion.
Drill and tap a pylon for what purpose???
This is potentially a risky high fatigue issue, since tapped threads are notoriously poor in tension-fatigue. I would be LESS agitated if I knew a thread-insert or stud was being installed and that it was for a low-stress/fatigue application...
Be extremely careful regarding base material type [aluminum is prone to chipping, CRES is prone to gummy/galling action and titanium is exceptionally hard], the tapping process [flood lubricant, tap quality/sharpness, depth of penetration, etc] and post-tap NDI [visual, measured-thread profile and eddy current or penetrant] for cracks, chips, irregular thread shape, etc.
Also strongly recommend You have an option if tapping operation is defective...
Regards, Wil Taylor
I worked many MIL acft and their weapons pylons... this is a very strange and potentially damaging action, in humble opinion.
Drill and tap a pylon for what purpose???
This is potentially a risky high fatigue issue, since tapped threads are notoriously poor in tension-fatigue. I would be LESS agitated if I knew a thread-insert or stud was being installed and that it was for a low-stress/fatigue application...
Be extremely careful regarding base material type [aluminum is prone to chipping, CRES is prone to gummy/galling action and titanium is exceptionally hard], the tapping process [flood lubricant, tap quality/sharpness, depth of penetration, etc] and post-tap NDI [visual, measured-thread profile and eddy current or penetrant] for cracks, chips, irregular thread shape, etc.
Also strongly recommend You have an option if tapping operation is defective...
Regards, Wil Taylor
DUKEOACES,
As mrainey noted, the UNJF (MIL-S-8879) threadform has a controlled root radius on the external threads, but the internal threads are very similar to a standard UNF thread except for the minor diameter tolerance. The 1.000-12 UNJF-3B thread is commonly used for MS type hydraulic ports, so the tap should be readily available. If not, having a custom tap made is very common.
While you didn't specify the thread class, MIL-S-8879 only has listings for a class 3 thread for your 1.000-12 size. Besides MIL-S-8879, FED-STD-H28 also gives some data on your particular thread.
UNJF class 3 threads also must meet tolerances for runout and pitch errors. So producing consistent quality 1.000-12 UNJF-3B threads with a tap might not be so easy. If you require more accurate threads, you might also consider milling them.
Good luck.
Terry
As mrainey noted, the UNJF (MIL-S-8879) threadform has a controlled root radius on the external threads, but the internal threads are very similar to a standard UNF thread except for the minor diameter tolerance. The 1.000-12 UNJF-3B thread is commonly used for MS type hydraulic ports, so the tap should be readily available. If not, having a custom tap made is very common.
While you didn't specify the thread class, MIL-S-8879 only has listings for a class 3 thread for your 1.000-12 size. Besides MIL-S-8879, FED-STD-H28 also gives some data on your particular thread.
UNJF class 3 threads also must meet tolerances for runout and pitch errors. So producing consistent quality 1.000-12 UNJF-3B threads with a tap might not be so easy. If you require more accurate threads, you might also consider milling them.
Good luck.
Terry
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