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Basics of thread

 

MORE INFORMATION?

Do you need more information about thread types or are you looking for a special solution? Please contact our Sales Engineers.

Teesing Sales Engineers

TEESING SALES ENGINEERS
Tel.   +31 70 413 07 50
Mail  sales@teesing.com

The most common types of UN (Unified National) thread are:

  • UNC – Unified National Coarse Thread, comparable with the ISO metric thread
  • UNF – Unified National Fine Thread

*Compared to standard threads (coarse thread), fine thread has a smaller pitch.

Unified threads come in three different classes:

1A (external) & 1B (internal): for applications where a liberal tolerance is required to permit easy assembly even with slightly nicked threads.
2A (external) & 2B (internal): most commonly used class for general applications.
3A (external) & 3B (internal): for applications where closeness of fit and/or accuracy of thread elements are important.

If you have any questions please contact us or check out our fittings with UNF thread. 

 

Flank angle is 60 °.
Female and male thread are both parallel.
Flank angle UNC/UNF

UNC (2A)

UNF (2A)

Nominal
diameter
Major 
diameter 
(mm)
Minor 
diameter
(mm)
TPI
1/4" x 20 UNC 6,322 4,978 20
5/16" x 18 UNC 7,907 6,401 18
3/8" x 16 UNC 9,491 7,798 16
7/16" x 14 UNC 11,076 9,144 14
1/2" x 13 UNC 12,661 10,592 13
5/8" x 11 UNC 15,834 13,386 11
3/4" x 10 UNC 19,004 16,307 10
7/8" x 9 UNC 22,176 19,177 9
1" x 8 UNC 25,349 21,971 8
2" x 4,5 UNC 50,726 44,679 4,5


Nominal 
diameter
Major 
diameter
(mm)
Minor 
diameter
(mm) 
TPI
1/4" x 28 UNF 6,325 5,360 28
5/16" x 24 UNF 7,910 6,782 24
3/8" x 24 UNF 9,497 8,382 24
7/16" x 20 UNF 11,079 9,728 20
1/2" x 20 UNF 12,667 11,328 20
5/8" x 18 UNF 15,839 14,351 18
3/4" x 16 UNF 19,012 17,323 16
7/8" x 14 UNF 22,184 20,269 14
1" x 12 UNF 25,354 23,114 12