Unified Thread Standard

from Wikipedia, the free encyclopedia
Three screws # 6 - 32 UNC with different screw heads . These screws with an outer diameter of 0.1380 inches (3.5052 mm), pitch 32 revolutions per inch, standard thread are used in computer cases , for example
Standard profile of UTS and ISO threads

The Unified Thread Standard is a standard for threads that is used in the United States and Canada .

The outer diameter of a screw is specified in inches and the thread pitch in revolutions per inch (instead of millimeters per revolution). The flank angle is 60 ° - just like with the metric ISO thread .

For diameters under 1 ⁄ 4 inches, the diameter is designated by a number defined in the standard from the following table. The designation (in the first column of the table) is spoken in English as "number", for example "number zero".

diameter
inch mm
# 0 0.0600 1.5240
#1 0.0730 1.8542
# 2 0.0860 2.1844
# 3 0.0990 2.5146
# 4 0.1120 2.8448
# 5 0.1250 3.1750
# 6 0.1380 3.5052
#8th 0.1640 4.1656
# 10 0.1900 4.8260
# 12 0.2160 5.4864

For all diameters from 1 ⁄ 4 inches, the value is given in inches or fractions of inches. The following gradations are common:

diameter
in inches
(fraction) 		in inches
(decimal) 		in mm
1 ⁄ 4 0.2500 06.3500
5 ⁄ 16 0.3125 07.9375
3 ⁄ 8 0.3750 09.5250
7 ⁄ 16 0.4375 11.1125
1 ⁄ 2 0.5000 12.7000
9 ⁄ 16 0.5625 14.2875
5 ⁄ 8 0.6250 15.8750
3 ⁄ 4 0.7500 19.0500
7 ⁄ 8 0.8750 22.2250
1 1.0000 25.4000

A distinction is made between the standard thread UNC (unified coarse) and the fine threads UNF (unified fine) and UNEF (unified extra fine). There is also the UNR and the UNS (unified special) for special cases. B. is used in microphone stands .

For example, the designation 1 ⁄ 2 -13 UNC means as much as outside diameter 0.5 inch, pitch 13 revolutions per inch, standard thread.

Many of the screw connections on western commercial aircraft (Boeing, Airbus, ...) are implemented as UNF threads.

Tolerance classes

As with metric threads, a distinction is also made here in order to meet different needs. Classes 1 (clearance fit) through 3 (H fit) to 5 (oversize fit) each with an appended "A" (external thread) or "B" (internal thread) specify a thread in this regard. For example 1 ⁄ 2 -13 UNC -3B.

literature

  • Standard ANSI / ASME B1.1-2003, Unified Inch Screw Threads (UN and UNR Thread Form)

Individual evidence

  1. ↑ Unified Coarse Thread at gewinde-normen.de
  2. ↑ Unified Fine Thread at gewinde-normen.de
  3. ↑ Unified Extra Fine Thread at gewinde-normen.de
  4. ↑ UNR thread ASME B1.1-2003 at gewinde-normen.de
  5. ↑ Unified Special Thread at gewinde-normen.de