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USS Flat Washer, Plated

Selected Grade 2 USS Flat Washer PlatedUSS Flat Washer, Plated
Grade 2 USS Flat Washer PlatedUSS Flat Washer, Plated

Low carbon USS flat washers, typically used with Grade 8 or hardened steel bolting, are used under bolt heads or nuts to increase the bearing surface area, or to offer protection so that the nut or bolt can be rotated without distortion of the bearing surface. Flat washers are also used to give tightness to a joint, to prevent leakage, and especially to distribute pressure under the head of a bolt or nut. Dimensional specifications are governed by ASME B18.21.1. USS (United States Standard) flat washers have a larger outer diameter than SAE (Society of Automotive Engineers) flat washers, and can be utilized in nearly any application. ASTM F844 covers the standard specifications for unhardened steel flat washers for general use. Available in zinc plated finish. Zinc plating sacrifices itself, corroding before the base material, offering added corrosion resistance.

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Dimensional Specifications

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USS Flat Washer dimensions
Per ASME B18.21.1-2009
Size Nominal A B C
Inside Diameter Outside Diameter Mean Section Thickness
Basic Tolerance
Plus		 Tolerance
Minus		 Basic Tolerance
Plus		 Tolerance
Minus		 Basic Max Min
#6 0.1380 0.1560 0.0080 0.0050 0.3750 0.0150 0.0050 0.0490 0.0650 0.0360
#8 0.1640 0.1880 0.0080 0.0050 0.4380 0.0150 0.0050 0.0490 0.0650 0.0360
#10 0.1900 0.2190 0.0080 0.0050 0.5000 0.0150 0.0050 0.0490 0.0650 0.0360
#12 0.2160 0.2500 0.0150 0.0050 0.5620 0.0150 0.0050 0.0650 0.0800 0.0510
1/4 0.2500 0.3120 0.0150 0.0050 0.7340 0.0150 0.0070 0.0650 0.0800 0.0510
5/16 0.3125 0.3750 0.0150 0.0050 0.8750 0.0300 0.0070 0.0830 0.1040 0.0640
3/8 0.3750 0.4380 0.0150 0.0050 1.0000 0.0300 0.0070 0.0830 0.1040 0.0640
7/16 0.4375 0.5000 0.0150 0.0050 1.2500 0.0300 0.0070 0.0830 0.1040 0.0640
1/2 0.5000 0.5620 0.0150 0.0050 1.3750 0.0300 0.0070 0.1090 0.1320 0.0860
9/16 0.5625 0.6250 0.0150 0.0050 1.4690 0.0300 0.0070 0.1090 0.1320 0.0860
5/8 0.6250 0.6880 0.0300 0.0070 1.7500 0.0300 0.0070 0.1340 0.1600 0.1080
3/4 0.7500 0.8120 0.0300 0.0070 2.0000 0.0300 0.0070 0.1480 0.1770 0.1220
7/8 0.8750 0.9380 0.0300 0.0070 2.2500 0.0300 0.0070 0.1650 0.1920 0.1360
1 1.0000 1.0625 0.0300 0.0070 2.5000 0.0300 0.0070 0.1650 0.1920 0.1360
1 1/8 1.1250 1.2500 0.0300 0.0070 2.7500 0.0300 0.0070 0.1650 0.1920 0.1360
1 1/4 1.2500 1.3750 0.0300 0.0070 3.0000 0.0300 0.0070 0.1650 0.1920 0.1360
1 3/8 1.3750 1.5000 0.0450 0.0100 3.2500 0.0450 0.1000 0.1800 0.2130 0.1530
1 1/2 1.5000 1.6250 0.0450 0.0100 3.5000 0.0450 0.0100 0.1800 0.2130 0.1530
1 5/8 1.6250 1.7500 0.0450 0.0100 3.7500 0.0450 0.0100 0.1800 0.2130 0.1530
1 3/4 1.7500 1.8750 0.0450 0.0100 4.0000 0.0450 0.0100 0.1800 0.2130 0.1530
1 7/8 1.8750 2.0000 0.0450 0.0100 4.2500 0.0450 0.0100 0.1800 0.2130 0.1530
2 2.0000 2.1250 0.0450 0.0100 4.5000 0.0450 0.0100 0.1800 0.2130 0.1530
2 1/4 2.2500 2.3750 0.0450 0.0100 4.7500 0.0450 0.0100 0.2200 0.2480 0.1930
2 1/2 2.5000 2.6250 0.0450 0.0100 5.0000 0.0450 0.0100 0.2380 0.2800 0.2100
2 3/4 2.7500 2.8750 0.0650 0.0100 5.2500 0.0650 0.0100 0.2590 0.3100 0.2280
3 3.0000 3.1250 0.0650 0.0100 5.5000 0.0650 0.0100 0.2840 0.3270 0.2490
  1. All dimensions are in inches.

Governing Standards

ASTM F844 Covers standard, unhardened steel washers for general use.
ASME B18.21.1 Covers the dimensional requirements, physical properties, and related test methods for helical spring-lock washers (#0 through 3 inches), tooth-lock washers (#2 through 1 ¼ inches), and plain washers (#0 through 3 inches).