What is the difference between NS & NF3 stand for threads

D

Dean Frederickson

I hope this will help you.

Unified class 1A/1B series. Class 1 fine thread series (NF-1) is approximately equivalent dimensionally to Unified class 2A/2B series. Standard Unified series threads should be considered prior to approval of replacement by non-standard threads.
b. American National class 2 coarse thread series (NC-2), 8 thread series (9N-2), 12 thread series (12N-2), 16 thread series (16N-2), and extra fine series (NEF-2) are most nearly equivalent to Unified series UNC-2A/2B, 8UN-2A/2B, 12UN-2A/2B, 16UN-2A/2B and UNEF-2A/2B, respectively. Class 2 fine thread series (NF-2) is approximately equivalent dimensionally to Unified class 3A/3B series, but the use of class 2A/2B series should be considered prior to approval of replacement by class 3A/3B.
c. American National class 3 series NC-3, NF-3, NEF-3, 8N-3, 12N-3 and 16N-3 are most nearly equivalent to Unified class 3 series UNC-3A/3B, UNF-3A/3B, UNEF-3A/3B, 8UN-3A/3B, 12UN-3A/3B, and 16UN-3A/3B, respectively.
d. There is no Unified thread class equivalent to the old American National class 4 which required selective fit of parts due to the possibility of interference.



c. American National class 3 series NC-3, NF-3, NEF-3, 8N-3, 12N-3 and 16N-3 are most nearly equivalent to Unified class 3 series UNC-3A/3B, UNF-3A/3B, UNEF-3A/3B, 8UN-3A/3B, 12UN-3A/3B, and 16UN-3A/3B, respectively.
 
M

msec0990

This is fairly late, but actually the "F" and the "S" are not similar at all. The "F" refers to fine threads (example: 1/4 - 28 UNF is considered a "fine" thread) as opposed to "C" for coarse (example: 1/4 - 20 UNC is a "coarse" thread.)

The "S" stands for "special" and I believe is only used for what are considered non-standard thread designations. For example, I found a 1/4 - 36 UNS-2B in a gage drawer. In all cases, the second number is TPI, or threads per inch.

I'm not sure that "UNSF" is a correct designation, simply because the two mean something different as noted above.

This is my interpretation. I'm not an expert, but I took a good seminar once. :lol:
 
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