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2HM Heavy Hex Nut
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2HM Heavy Hex Nut

2HM Heavy Hex Nut

ASTM A194 Grade 2HM heavy hex nuts are quenched and tempered alloy steel nuts and are 100% hardness tested. ASTM A194 covers carbon steel, alloy steel, and stainless steel nuts for bolts in high pressure or high temperature service. They are usually paired with A193 Grade B7M fasteners in applications where hydrogen sulfide gas exposure may lead to hydrogen embrittlement problems. Dimensional specifications are governed by ASME B18.2.2. Heavy hex nuts provide increased bearing surface area over finished nuts such as J995 Grade 5 nuts.

Governing StandardsGrade 2HM

ASTM A194 This specification covers a variety of carbon, alloy, and martensitic stainless steel nuts in the size range 1⁄4 through 4 in. and metric M6 through M100 nominal. It also covers austenitic stainless steel nuts in the size range 1⁄4 in. and M6 nominal and above. These nuts are intended for high-pressure or high temperature service, or both. Grade substitutions without the purchaser’s permission are not allowed.
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 2HM Head Marking
Grade 2HM Material Marking

Mechanical PropertiesGrade 2HM

Carbon Steel, Quenched & Tempered, 100% Hardness Tested Per ASTM A194/A194M-16
Proof Load Stress (psi) min Hardness Hardness Tempering Temperature
Min psi Brinell Rockwell (B Scale) Min
150,000 159 to 235 84 to 99 1150F
150,000 159 to 235 84 to 99 1150F

Chemical PropertiesGrade 2HM

Per ASTM A194/A194M-16
Grade Material Carbon Manganese Phosphorus Sulfur (1) Silicon
% by weight % by weight % by weight % by weight % by weight
2HM Carbon Steel 0.40 min 1.00 max 0.040 max 0.050 max 0.04 max
  1. 1. Because of the degree to which sulfur segregates, product analysis for sulfur over 0.060 % max is not technologically appropriate.

Dimensional SpecificationsGrade 2HM

Heavy hex nut dimensions
Per ASME B18.2.2-2015
Nominal Diameter UNC UN8 F G H
Width Across Flats Width Across Corners Thickness
Basic Max Min Max Min Basic Max Min
1/4 0.250 20   1/2 0.500 0.488 0.577 0.556 15/64 0.250 0.218
5/16 0.313 18   9/16 0.562 0.546 0.650 0.220 19/64 0.314 0.280
3/8 0.375 16   11/16 0.688 0.669 0.794 0.763 23/64 0.377 0.341
7/16 0.438 14   3/4 0.750 0.728 0.866 0.830 27/64 0.441 0.403
1/2 0.500 13   7/8 0.875 0.850 1.010 0.990 31/64 0.504 0.464
9/16 0.563 12   15/16 0.938 0.909 1.083 1.037 35/64 0.568 0.526
5/8 0.625 11   1 1/16 1.062 1.031 1.227 1.175 39/64 0.631 0.587
3/4 0.750 10   1 1/4 0.250 1.212 1.443 1.382 47/64 0.758 0.710
7/8 0.875 9   1 7/16 1.438 1.394 1.660 1.589 55/64 0.885 0.833
1 1.000 8   1 5/8 1.625 1.575 1.876 1.796 63/64 1.012 0.956
1 1/8 1.125 7 8 1 13/16 1.812 1.756 2.093 2.002 1 7/64 1.139 1.079
1 1/4 1.250 7 8 2 2.000 1.380 2.309 2.209 1 7/32 1.251 1.187
1 3/8 1.375 6 8 2 3/16 2.188 2.119 2.526 2.416 1 11/32 1.378 1.310
1 1/2 1.500 6 8 2 3/8 2.375 2.300 2.742 2.622 1 15/32 1.505 1.433
1 5/8 1.625 5 1/2 8 2 9/16 2.562 2.481 2.959 2.828 1 19/32 1.632 1.556
1 3/4 1.750 5 8 2 3/4 2.750 2.662 3.175 3.035 1 23/32 1.759 1.679
1 7/8 1.875 5 8 2 15/16 2.938 2.844 3.392 3.242 1 27/32 1.886 1.802
2 2.000 4 1/2 8 3 1/8 3.125 3.025 3.608 3.449 1 31/32 2.013 1.925
2 1/4 2.250 4 1/2 8 3 1/2 3.500 3.388 4.041 3.862 2 13/64 2.251 2.155
2 1/2 2.500 4 8 3 7/8 3.875 3.750 4.474 4.275 2 29/64 2.505 2.401
2 3/4 2.750 4 8 4 1/4 4.250 4.112 4.907 4.688 2 45/64 2.759 2.647
3 3.000 4 8 4 5/8 4.625 4.475 5.340 5.102 2 61/64 3.013 2.893
3 1/4 3.250 4 8 5 5.000 4.838 5.774 5.515 3 3/16 3.252 3.124
3 1/2 3.500 4 8 5 3/8 5.375 5.200 6.207 5.928 3 7/16 3.506 3.370
3 3/4 3.750 4 8 5 3/4 5.750 5.562 5.562 6.341 3 11/16 3.670 3.616
4 4.000 4 8 6 1/8 6.125 5.925 5.925 6.755 3 15/16 4.014 3.862
  1. All dimensions are in inches.
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Thread Pitch

2HM Heavy Hex Nut
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Diameter Thread Pitch Width Across Flats Height of Nut Item # Availability Price Quantity UOM
1/2 13 7/8 0.4844 N2HM0500000-I In Stock $0.35311/EA EA
5/8 11 1 1/16 0.6094 N2HM0620000-I In Stock $1.1414/EA EA
3/4 10 1 1/4 0.7344 N2HM0750000-I In Stock $0.70539/EA EA
7/8 9 1 7/16 0.8594 N2HM0870000-I In Stock $2.10639/EA EA
1 8 1 5/8 0.9844 N2HM1000000-I In Stock $1.27095/EA EA