UNIFIED THREADS OF SPECIAL DIAMETERS,
PITCHES AND LENGTH OF ENGAGEMENT
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FED-STD-H28/3(31 MAR 1978) - Thread data are calculated for certain special combinations of diameter and pitch, with pitch diameter tolerances based on a thread engagement length of 9 x Pitch. The pitch diameter limits are applicable for a length of engagement of 5 to 15 times the pitch. (The length of thread on mating parts, however, may exceed the length of engagement by a large amount) These threads are designated by UNS and UNRS. These are included in the Unified Standard Series.
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| EXTERNAL |
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MAJOR Ø |
MAJOR Ø |
PITCH Ø |
PITCH Ø |
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| CLASS |
ALLOWANCE |
TOL |
MAX |
MIN |
MAX |
MIN |
TOL |
MINOR Ø |
| 1A |
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| 2A |
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| 3A |
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| INTERNAL |
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MINOR Ø |
MINOR Ø |
PITCH Ø |
PITCH Ø |
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| CLASS |
ALLOWANCE |
TOL |
MIN |
MAX |
MIN |
MAX |
TOL |
MAJOR Ø |
| 1B |
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| 2B |
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| 3B |
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