SS Coupling Nut
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SS Coupling Nut

18-8 stainless steel hex coupling nuts are made from one of the following austenitic alloys: 303, 303Se, 304, XM7, all of which are characterized as having a chromium content of 17-19% and nickel content of 8-10%. Dimensional specifications are governed by ASME B18.2.2. There are no grade markings on 18-8 stainless hex coupling nuts. Coupling nuts, also known as extension nuts, are used for joining two male threads, usually threaded rods, in a variety of applications. 300 series stainless steel fasteners are commonly used in applications that require general atmospheric corrosion resistance, such as chemical and food processing equipment. Stainless steel has a higher corrosion resistance than carbon steel.

Governing Standards18-8 Stainless Steel

ASME B18.2.2 Covers the complete general and dimensional data for the various types of inch series square and hex nuts, including machine screw nuts and coupling nuts.
ASME B1.1 UNC & UNF Class 2B Specifies the thread form, series, class, allowance, tolerance, and designation for unified screw threads.

Grade A & Grade 2 Marking
18-8 Stainless Steel requires no material marking

Dimensional Specifications18-8 Stainless Steel

Hex coupling nut dimensions
Per ASME B18.2.2-2015
Nominal Diameter UNC UNF F G
Flat to Flat Thickness
#4 0.1380 40 48 5/16 7/16
#6 0.1380 32 40 5/16 1/2
#8 0.1640 32 38 5/16 1/2
#10 0.1900 24 32 3/8 3/4
1/4 0.2500 20 28 3/8 7/8
5/16 0.3125 18 28 7/16 1
3/8 0.3750 16 24 1/2 1 1/8
7/16 0.4375 14 20 9/16 1 1/4
1/2 0.5000 13 20 5/8 1 1/4
5/8 0.6250 11 18 0.875 1 3/4
3/4 0.7500 10 16 1 2
7/8 0.8750 9 14 1 1/4 2 1/2
1 1.0000 8 12 1 3/8 2 1/2
1 1/8 1.1250 7 12 1 1/2 3
1 1/4 1.2500 7 12 1 5/8 3
1 1/2 1.5000 6 12 2 3 1/2
  1. All dimensions are in inches.
SS Coupling Nut
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Diameter Thread Pitch Width Across Flats Length Item # Availability Price Quantity UOM
1/4 20 3/8 7/8 NCOU025SS In Stock $1.03425/EA EA
5/16 18 7/16 1 NCOU031SS In Stock $1.30308/EA EA
3/8 16 1/2 1 1/8 NCOU037SS In Stock $1.39078/EA EA
1/2 13 5/8 1 1/4 NCOU050SS In Stock $2.31841/EA EA
5/8 11 7/8 1 3/4 NCOU062SS In Stock $8.47923/EA EA
3/4 10 1 2 NCOU075SS In Stock $11.61398/EA EA