steel nuts e1548871284441

Hex Steel Nuts & Washers for Stud Bolts (ASTM A194 2/2H/4/7)

steel nuts e1548871284441

Hex Steel Nuts & Washers for Stud Bolts (ASTM A194 2/2H/4/7)

The ASTM A194 material grades specifications and dimensional charts for hexagonal steel nuts for stud bolts charts



Nuts and washers play crucial roles in the effectiveness and longevity of stud bolt connections in various applications, from general construction to high-pressure and high-temperature environments like those found in the petrochemical industry.

nuts and washers for stud bolts
nuts and washers for stud bolts

Here’s an overview of their functions and types:

Nuts for Stud Bolts

Nuts are paired with stud bolts to apply clamping force across the connected parts. They engage with the threaded ends of stud bolts, allowing for the adjustment of tension and holding components securely together. The most common types of nuts used with stud bolts include:

  • Hex Nuts: The most common type, offering a good balance of size, shape, and ease of use. They are typically used in pairs, with one nut on each end of the stud bolt.
  • Heavy Hex Nuts: Larger and thicker than standard hex nuts, providing more robust engagement with the stud bolt and distributing the load over a larger area, which is beneficial in high-pressure applications.
  • Lock Nuts: Designed to prevent loosening under vibration and torque. They can have various features for locking, including nylon inserts (nyloc nuts) or distorted threads.

Washers for Stud Bolts

Washers distribute the load of a nut or bolt head over a larger area, which can help prevent the bolt head or nut from digging into the surfaces of the connected parts. They also protect the surface of the assembled parts from damage during the tightening process. Moreover, washers can help to maintain preload and ensure the reliability of the bolted connection under thermal expansion and contraction. Common types of washers include:

  • Flat Washers: The most basic type, used to distribute the load over a broader area and to prevent damage to the surface material.
  • Spring Washers (Belleville Washers): Conical-shaped washers that provide a spring force between the head of the bolt and the substrate, helping to maintain the bolt’s tension in applications subject to vibrations.
  • Lock Washers: Intended to prevent the nut from loosening. They can have a split (helical spring washer) or toothed design to grip the nut and the mounting surface.

Application Considerations

The choice of nuts and washers for stud bolts depends on several factors, including the mechanical requirements of the connection (e.g., load-bearing capacity), environmental conditions (e.g., temperature, presence of corrosive elements), and specific application requirements (e.g., vibration resistance). Materials commonly used for nuts and washers include carbon steel, stainless steel, and alloys designed for specific environmental resistances.

In high-stress or critical applications, such as flanged connections in the oil and gas industry, the correct selection and installation of nuts, washers, and stud bolts are vital for ensuring the integrity and safety of the connection. Proper maintenance and regular inspection are also crucial to prevent failure and extend the service life of these connections.


The chart below shows the hex nuts’ width and thicknesses by diameter:

Heavy Hex Nuts Dimensions ASME B18.2.2
Heavy Hex Nuts Dimensions ASME B18.2.2
Across Flats
Across Corners
Heavy Hex Nuts Dimensions ASME B18.2.2
Heavy Hex Nuts Dimensions ASME B18.2.2
HEAVY HEX NUT DIAMETER (inches)Hex Heavy Nut Thickness



Hex nuts weight in Lbs (pounds/ 100 pieces) by diameter:

Heavy Hex Nuts DiameterFinished HexHeavy HexFinished JamHeavy Hex JamSquareHeavy Square
1-5/8″ 162 91.6  
1-7/8″ 241 134  
2-1/4″ 419 227  
2-1/2″ 564 332  
2-3/4″ 738 429  
3″ 950 545  
3-1/4″ 1194 651  
3-1/2″ 1526 851  
3-3/4″ 1812 1005  
4″ 2180 1200  

The weight of heavy hexagonal steel nuts for stud bolts in lbs / 100 units – ASME B18.2.2


Hex nuts weight in Kgs. (kg/100 pieces) by diameter:

Heavy Hex Nuts DiameterFinished HexHeavy HexFinished JamHeavy Hex JamSquareHeavy Square
1-7/8″0.00109.290.0060.77 0.00
2″101.58135.6063.4974.83 0.00
2-1/4″ 190.020.00102.94 0.00
2-1/2″ 255.770.00150.56 0.00
2-3/4″ 334.680.00194.55 0.00
3″ 430.830.00247.16 0.00
3-1/4″ 541.480.00295.23 0.00
3-1/2″ 692.040.00385.93 0.00
3-3/4″ 821.740.00455.77 0.00
4″ 988.630.00544.20  
The weight of heavy hexagonal steel nuts for stud bolts in kilograms / 100 units – ASME B18.2.2


Complete stud bolt assembly weight in Kgs. (kg/100 pieces) by metric size:

Heavy Hex Nuts Diameter (Metric)Bolt Weight (kg)Nut Weight (kg)Total Weight (kg)
M12 x 350.0490.0130.062
M12 x 400.0530.0130.066
M12 x 450.0580.0130.071
M12 x 500.0620.0130.075
M12 x 550.0670.0130.080
M12 x 600.0710.0130.084
M12 x 650.0720.0130.085
M12 x 700.0800.0130.093
M12 x 750.0850.0130.098
M12 x 800.0890.0130.102
M12 x 850.0940.0130.107
M12 x 900.0980.0130.111
M12 x 950.1030.0130.116
M12 x 1000.1070.0130.120
M12 x 1050.1110.0130.124
M12 x 1100.1160.0130.129
M 16X350.0870.0320.119
M 16X400.0940.0320.126
M 16X450.1020.0320.134
M 16X500.1100.0320.142
M 16X550.1180.0320.150
M 16X600.1260.0320.158
M 16X650.1320.0320.164
M 16X700.1410.0320.173
M 16X750.1480.0320.180
M 16X800.1530.0320.185
M 16X850.1610.0320.193
M 16X900.1670.0320.199
M 16X950.1770.0320.209
M 16X1000.1860.0320.218
M 16X1050.1950.0320.227
M 16X1100.2030.0320.235
M 16X1150.2110.0320.243
M 16X1200.2200.0320.252
M 16X1250.2280.0320.260
M 16X1300.2350.0320.267
M 16X1350.2430.0320.275
M 16X1400.2510.0320.283
M 16X1450.2590.0320.291
M 16X1500.2670.0320.299
M 16X1550.2700.0320.302
M 16X1600.2780.0320.310
M 16X1650.2860.0320.318
M 16X1700.2940.0320.326
M 16X1750.3020.0320.334
M 16X1800.3100.0320.342
M 16X1850.3180.0320.350
M 16X1900.3260.0320.358
M 16X1950.3340.0320.366
M 16X2000.3420.0320.374
M 20X450.1730.0610.234
M 20X500.1860.0610.247
M 20X550.1980.0610.259
M 20X600.2110.0610.272
M 20X650.2230.0610.284
M 20X700.2350.0610.296
M 20X750.2480.0610.309
M 20X800.2600.0610.321
M 20X850.2730.0610.334
M 20X900.2850.0610.346
M 20X950.2970.0610.358
M 20X1000.3100.0610.371
M 20X1050.3220.0610.383
M 20X1100.3340.0610.395
M 20X1150.3460.0610.407
M 20X1200.3590.0610.420
M 20X1250.3710.0610.432
M 20X1300.3840.0610.445
M 20X1350.3960.0610.457
M 20X1400.4080.0610.469
M 20X1450.4210.0610.482
M 20X1500.4330.0610.494
M 20X1550.4450.0610.506
M 20X1600.4580.0610.519
M 20X1650.4700.0610.531
M 20X1700.4820.0610.543
M 20X1750.4950.0610.556
M 20X1800.5060.0610.445
M 20X1850.5180.0610.457
M 20X1900.5300.0610.469
M 20X1950.5420.0610.481
M 20X2000.5540.0610.493
M 24X450.2580.1040.362
M 24X500.2760.1040.380
M 24X550.2940.1040.398
M 24X600.3120.1040.416
M 24X650.3300.1040.434
M 24X700.3480.1040.452
M 24X750.3660.1040.470
M 24X800.3840.1040.488
M 24X850.4020.1040.506
M 24X900.4200.1040.524
M 24X950.4370.1040.541
M 24X1000.4560.1040.560
M 24X1050.4710.1040.575
M 24X1100.4920.1040.596
M 24X1150.5100.1040.614
M 24X1200.5280.1040.632
M 24X1250.5460.1040.650
M 24X1300.5590.1040.663
M 24X1350.5820.1040.686
M 24X1400.5980.1040.702
M 24X1450.6180.1040.722
M 24X1500.6380.1040.742
M 24X1550.6560.1040.760
M 24X1600.6740.1040.778
M 24X1650.6880.1040.792
M 24X1700.7090.1040.813
M 24X1750.7270.1040.831
M 24X1800.7450.1040.849
M 24X1850.7620.1040.866
M 24X1900.780.1040.884
M 24X1950.7980.1040.902
M 24X2000.8160.1040.920



The ASTM A194 specification covers a variety of carbon, alloy, martensitic and austenitic stainless steel nuts. Hex-heavy nuts are components of boltings sets for flanges.

These nuts are intended for high-pressure or high-temperature service or both. Bars from which the nuts are made shall be hot-wrought.

According to the ASTM A194 norm, the material may be further processed by centerless grinding or by cold drawing.

Austenitic stainless steel may be solution annealed or annealed and strain-hardened. Each alloy shall conform to the chemical composition requirements prescribed.

Hardness tests, proof of load tests, and cone-proof load tests shall be made to all nuts to meet the requirements specified.

ASTM A194 stated that either inch-pound units or SI units are to be regarded separately as standard.
The values stated in each system are not exact equivalents; therefore, each system must be used independently by the other. Combining values from the two systems may result in a non-conformity with the specification of the ASTM A194 norm.
Within the text, the SI units are shown in brackets. ASTM A194  covers the size from 1/4 inch. through 4 inches. and the metric sizes between M6 and M100 nominal diameter. It also covers austenitic stainless steel nuts in the size range 1/4 inch. and M6 nominal and upper.
Unless otherwise specified, the American National Standard Heavy Hex Series (ANSI B 18.2.2) shall be used for the threading of the nuts. Heavy hex nuts > =  1 inch. nominal size shall be UNC Series Class 2B fit.
Nuts over 1 inch. nominal size shall be either UNC Series Class 2B fit or 8 UN Series Class 2B fit. High-strength ASTM A194 grade 2H nuts are the most common type of steel nuts used in combination with A193 B7 stud bolts.
The most common grades of ASTM A194 heavy hex steel nuts are:
  • ASTM A194 2H: Quenched & tempered carbon steel heavy hex nuts
  • ASTM A194 2HM: Quenched & tempered carbon steel heavy hex nuts
  • ASTM A194 4: Quenched & tempered carbon-molybdenum heavy hex nuts
  • ASTM A194 3
  • ASTM A194 6
  • ASTM A194 7: Quenched & tempered alloy steel heavy hex nuts
  • ASTM A194 7M: Quenched & tempered alloy steel heavy hex nuts
  • ASTM A194 8: Stainless AISI 304 heavy hex nuts
  • ASTM A194 8A
  • ASTM A194 8M: Stainless AISI 316 heavy hex nuts
  • ASTM A194 8MA
  • ASTM A194 8C
  • ASTM A194 8T

ASTM A194 Chemical Composition

ASTM A194 NUTSCarbonManganesePhosphorous, maxSulfur, maxSiliconChromiumNickelMolybdenumOther Elements
ASTM A194 grade 2, 2H and 2 HM0.40% min.1.00% max.0.04%0.05%0.40% max    
ASTM A194 grade 30.10% min.1.00% max.0.04%0.03%1.00%4.0-6.0% 0.20-0.30% 
ASTM A194 grade 40.40 -0.50%0.70-0.90%0.035%0.04%0.15-0.35%  0.20-0.30% 
ASTM A194 grade 60.15%1.00%0.04%0.03%1.00%11.5-13.5%   
ASTM A194 grade 6F0.15%1.25%0.06%0.06%1.00%12.0-14.0%  Selenium-0.15% min
ASTM A194 grade 7 and 7M (AISI 4140)0.37-0.49%0.65-1.10%0.04%0.04%0.15-0.035%0.75-1.20% 0.15-0.25% 
ASTM A194 grade 8 (AISI 304)0.08%2.00% max0.05%0.03%1.00% max18.0-20.0%8.0-11.0%  
ASTM A194 grade 8M (AISI 316)0.08%2.00% max0.05%0.30%1.00% max16.0-18.0%10.0-14.0%2.00-3.00% 
ASTM A194 grade 8C0.08%2.00%0.045%0.03%1.00%17.0-19.0%9.0-12.0% Columbium and Tantalum – 10x carbon content, min
ASTM A194 grade 8T0.80%2.00%0.045%0.30%1.00%17.0-19.0%9.0-12.0% Titanium-0.70%max, Nitrogen-0.10%
ASTM A194 grade 8F0.15%2.00%0.20%0.15%min1.00%17.0-19.0%8.0-10.0%  
ASTM A194 grade 8R0.06%4.0-6.0%0.045%0.03%1.00%20.5-23.5%11.5-13.5%1.50-3.00%Columbium and Tantalum-0.10-0.30%, Nirogen-0.20-0.40%, Vanadium-0.10-0.30%
ASTM A194 grade 8S0.10%7.0-9.0%0.060%0.03%3.5-4.5%16.0-18.0%8.0-9.0% Nitrogen-0.08-0.18%
ASTM A194 grade 160.36-0.47%0.45-0.70%0.035%0.40%0.15-0.35%0.80-1.15% 0.50-0.65% 

ASTM A194 Mechanical Properties

Grade Identification Marking5SpecificationMaterialNominal Size, In.Tempering Temp. °FProof Load Stress, ksiHardness RockwellSee Note
ASTM A194 Gr 2ASTM A194 Grade 2Medium Carbon Steel1/4 – 401501593521,2,3
ASTM A194 Gr 2HASTM A194 Grade 2HMedium Carbon Steel, Quenched and Tempered1/4 – 4850175C24C381,2
ASTM A194 Gr 2HMASTM A194 Grade 2HMMedium Carbon Steel, Quenched and Tempered1/4 – 411501501592371,2,3
ASTM A194 Gr 4ASTM A194 Grade 4Medium Carbon Alloy Steel, Quenched and Tempered1/4 – 41100175C24C381,2
ASTM A194 Gr 7ASTM A194 Grade 7Medium Carbon Alloy Steel, Quenched and Tempered1/4 – 41100175C24C381,2
ASTM A194 Gr 7MASTM A194 Grade 7MMedium Carbon Alloy Steel, Quenched and Tempered1/4 – 411501501592371,2,3
ASTM A194 Gr 8ASTM A194 Grade 8Stainless AISI 3041/4 – 4801263004
ASTM A194 Gr 8MASTM A194 Grade 8MStainless AISI 3161/4 – 4801263004



  • Scope: Provides specifications for carbon and alloy steel nuts.
  • Grades: Offers a range of grades including Grade A (mild carbon steel), Grade C (medium carbon, quenched and tempered), Grade DH (carbon steel, quenched and tempered), and others, suitable for general use to high-strength applications.


  • Scope: Covers the requirements for stainless steel nuts used in general engineering applications.
  • Grades: Classifies nuts based on alloy groups such as 304, 316, and 321, with conditions indicating the strength level (CW – cold worked, A – annealed).


  • Scope: This specification is for nonferrous nuts for general use, made from materials like aluminum, copper, and nickel alloys.
  • Grades: Nuts are categorized by the material and its temper, e.g., Aluminum Alloy 6061-T6.

ASTM A563M (Metric)

  • Scope: The metric companion to ASTM A563, covering carbon and alloy steel nuts in metric sizes.
  • Grades: Similar to ASTM A563 but tailored for metric dimensions and strength classes.


  • Scope: The metric version of ASTM F594, specifies stainless steel nuts in metric sizes for general engineering use.
  • Grades: Classified by alloy group and condition, similar to ASTM F594 but in metric measurements.


In Europe, the specifications for hexagonal nuts used with flanges are defined by several standards, ensuring compatibility and performance across various applications, particularly in the industrial, construction, and energy sectors. Here are some of the key European specifications:

1. EN ISO 4032

  • Scope: This standard specifies the characteristics of hexagonal nuts, style 1, with threads from M1.6 up to and including M64, of product grade A for threads ≤ M16 and product grade B for threads > M16.
  • Applications: These nuts are generally used for all types of flanged connections.

2. EN ISO 4033

  • Scope: Similar to EN ISO 4032 but specifies the characteristics of hexagonal high nuts.
  • Applications: Used where longer thread engagement is necessary or for aesthetic reasons in various assemblies, including flanged connections.

3. EN ISO 4034

  • Scope: Specifies the characteristics of hexagonal nuts, style 1, with threads from M5 up to and including M39, of product grade C.
  • Applications: Suitable for less critical applications where a coarse tolerance is acceptable.

4. EN ISO 4035

  • Scope: This standard covers hexagon thin nuts (chamfered) with metric fine-pitch thread, product grades A and B.
  • Applications: Used in applications where space constraints require a thinner nut, including some flange connections.

5. EN ISO 4036

  • Scope: Specifies hexagon thin nuts (unchamfered) with metric fine-pitch thread, product grades A and B.
  • Applications: Similar to EN ISO 4035, for applications needing a thin nut without a chamfer, such as certain flanged joints.

6. EN 1092-1:

While primarily focused on flanges and their joints, EN 1092-1 indirectly sets requirements for bolts and nuts used in flanged connections by specifying flange types, dimensions, and materials suitable for various pressure and temperature conditions.

Common ISO Grades for Nuts

In Europe, steel nuts and other fasteners are commonly classified according to ISO standards, which provide a uniform framework for specifications across international borders. The material grades for steel nuts under the ISO standards are designated to match specific mechanical properties, corrosion resistance, and intended use environments. Here are some common European material grades for steel nuts according to ISO:

ISO 898-2 for Carbon Steel and Alloy Steel Nuts

  • Class 6: A low-strength grade used for light-duty applications where high tensile strength is not required.
  • Class 8: A medium strength grade, widely used for general engineering applications.
  • Class 10: A high-strength grade suitable for applications requiring good tensile strength and hardness.
  • Class 12: Similar to Class 10 but with higher tensile strength and hardness for more demanding applications.

ISO 3506-2 for Stainless Steel Nuts

A1, A2, A4 Stainless Steel:

  • A2 (AISI 304 equivalent): The most commonly used stainless steel grade for nuts, offering good corrosion resistance in standard environments. Suitable for both indoor and outdoor applications.
  • A4 (AISI 316 equivalent): Offers enhanced corrosion resistance compared to A2, making it ideal for marine and chemical exposure environments due to the addition of molybdenum.

Tensile/Yield Strength Classification (8.8/10.9 Nuts)

The ISO 898 grading system for mechanical properties of hex nuts for flanges is a two-number system where:

  • The first number multiplied by 100 gives the approximate minimum ultimate tensile strength in megapascals (MPa).
  • The second number (when multiplied by the first number) gives the ratio of the yield strength to the tensile strength.

8.8 Grade Steel Nuts:

  • Tensile Strength: The “8” in 8.8 indicates that the tensile strength is 800 MPa.
  • Yield Strength: The “.8” indicates that the yield strength is 0.8 times the tensile strength, which calculates to approximately 640 MPa (0.8 x 800 MPa).
  • Material and Coating: These are made from medium carbon steel or alloy steel and can be heat-treated. They may be coated with zinc or other protective coatings to enhance corrosion resistance.
  • Applications: Grade 8.8 nuts are commonly used in automotive applications, construction, and manufacturing, where moderate levels of strength and toughness are required.

10.9 Grade Steel Nuts:

  • Tensile Strength: The “10” in 10.9 indicates that the tensile strength is 1000 MPa.
  • Yield Strength: The “.9” indicates that the yield strength is 0.9 times the tensile strength, which calculates to approximately 900 MPa (0.9 x 1000 MPa).
  • Material and Coating: These are typically made from alloy steel and undergo a heat treatment process to achieve higher strength levels. Like the 8.8 grade, 10.9 nuts can also receive coatings for corrosion resistance.
  • Applications: Grade 10.9 nuts are used in applications requiring high strength and durability, such as in heavy machinery, and structural applications, and where high loading is expected.

Key Considerations for Selection:

Application Requirements: Consider the mechanical loads, environmental conditions, and whether the application requires specific properties like corrosion resistance or prevailing torque.

Corrosion Resistance: Choose between A2 or A4 stainless steel grades based on the environmental exposure, with A4 being preferred for harsher conditions such as marine environments.

Mechanical Properties: Select the class (for carbon and alloy steel nuts) based on the required strength and application stress levels.

**DISCLAIMER: Accuracy and Reliability of Content**

The information provided in this blog post is intended for general informational purposes only and should not be construed as professional advice. While we strive to provide accurate and up-to-date information, we make no representations or warranties of any kind, express or implied, about the completeness, accuracy, reliability, suitability, or availability of the content contained herein. Any reliance you place on the information presented in this blog post is strictly at your own risk. We disclaim any liability for any loss or damage, including without limitation, indirect or consequential loss or damage, or any loss or damage whatsoever arising from reliance on information contained in this blog post. We encourage readers to verify the accuracy and relevance of any information presented here with other sources and seek professional advice or guidance where appropriate. Links to third-party websites or resources provided in this blog post are for convenience only and do not imply endorsement or approval of the content, products, services, or opinions expressed on those websites. We have no control over the nature, content, and availability of those sites and assume no responsibility for their accuracy, legality, or decency. We reserve the right to modify, update, or remove any content in this blog post at any time without prior notice. By accessing and using this blog post, you acknowledge and agree to these terms and conditions. If you do not agree with these terms, please refrain from accessing or using the information provided herein.

About the Author

Picture of Projectmaterials Team

Projectmaterials Team is an online resource dedicated to providing in-depth information, analysis, and educational content related to the fields of project materials management, engineering, and procurement, particularly within the oil & gas, construction, shipbuilding, energy, and renewable energy sectors. It aims to serve professionals and enthusiasts in these industries by offering valuable insights into materials, equipment, and techniques used in various projects, focusing on the selection, application, and maintenance of these resources. Key features of the blog include: * Educational Articles: Comprehensive posts that cover topics ranging from the technical aspects of piping products (pipes, valves, fittings, flanges, gaskets, bolts, instrumentation) to structural steel and process equipment (including oil extraction systems, drilling rigs, wellheads, pumps, compressors, and separation systems). * Industry Insights: Updates on the latest trends, technologies, and regulatory changes affecting the industries covered. * Guides and How-Tos: Practical advice on selecting the right materials and equipment for specific applications, as well as tips on installation, maintenance, and troubleshooting. * Safety and Standards: Information on safety equipment for production sites, risk mitigation procedures, and an overview of relevant industry standards and regulatory frameworks. The website is designed to support the professional development of engineers, procurement specialists, project managers, and other stakeholders involved in project plant businesses, by disseminating critical know-how and best practices. Whether readers are new to the field or seasoned professionals, offers resources to enhance their understanding and performance in managing project materials effectively.

Should you wish to reach out to the author of this article, we invite you to contact us via email

3 Responses

  1. is there any codes (ASME, ASTM, etc.) recommend pairing of bolt and nut type (i.e B7 bolt & 2H nut)

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.