Hardware

Nuts

The recommended nut specification for A307 is ASTM A563 Grade A. This is a low-strength steel nut that can be made in either hex or heavy hex patterns. For A307 grades A and C the recommended nut pattern is finished hex up through 1-1/2” in diameter. Above 1-1/2” diameter the nuts should be a heavy hex pattern. For A307 Grade B, all nuts are to be heavy hex pattern no matter the diameter. 

Nuts Washers
A307 Grades A & C* A307 Grade B
1/4 – 1-1/2 1-5/8 – 4 1/4 – 4
A563A Hex A563A Heavy Hex A563A Heavy Hex F844

Mechanical Properties

Grade Style Size, in. Proof Load, ksi Hardness, HBN
Plain Galvanized
A Hex 1/4 – 1-1/2 90 68 116 – 302
Heavy Hex 1/4 – 4 100 75 116 – 302

Chemical Properties

Element Grade A
Carbon 0.55% max
Manganese, min
Phosphorus, max 0.12%
Sulfur, max 0.15%*
* Sulfur content of 0.23% max is acceptable with the purchasers approval

Dimensions

Click table to show drawingHeavy Hex Nut
Nominal Size F C H Part Numbers
Width Across Flats Width Across Corners Thickness Domestic Import
Basic Max Min Max Min Basic Max Min Plain Galvanized Plain Galvanized
12 34 0.750 0.736 0.866 0.840 716 0.448 0.427 16270 16271 11701 11702
58 1516 0.938 0.922 1.083 1.051 3564 0.559 0.535 16272 16273 11703 11704
34 118 1.125 1.088 1.299 1.240 4164 0.665 0.617 16274 16275 11705 11706
78 1516 1.312 1.269 1.516 1.447 34 0.776 0.724 16276 16277 11707 11708
1 112 1.500 1.450 1.732 1.653 5564 0.887 0.831 16278 16279 11709 11710
118 11116 1.688 1.631 1.949 1.859 3132 0.999 0.939 16280 16281 11711 11712
114 178 1.875 1.812 2.165 2.066 1116 1.094 1.030 16282 16283 11713 11714
138 2116 2.062 1.994 2.382 2.273 11164 1.206 1.138 11715 11716
112 214 2.250 2.175 2.598 2.480 1932 1.317 1.245 16286 16287 11717 11718

Dimensions per ASME B18.2.2 1987 (1999)

Washers

The recommended washer for A307 bolts is an ASTM F844 USS pattern cut washer.  This is an unhardened washer, typically with a larger outside diameter than a structural washer, and is used for general purposes.  These washers do not have any mechanical or chemical requirements.  Dimensions are typically supplied per ASME B18.21.1.