ASTM F3394/F3394M-23

Standard Specification for Hardened Steel Backup and Reaction Washers Inch and Metric Dimensions<rangeref></rangeref >

SCOPE
1.1 This specification covers the chemical, mechanical, and dimensional requirements for hardened steel Backup and Reaction washers for use with fasteners having nominal diameters of 1/2 in. through 3 in. and M14 through M80. These washers are intended for general-purpose mechanical and structural use with bolts, nuts, studs, DTIs, and other internally and externally threaded fasteners. These washers are suitable for use with fasteners covered in Specifications A354, A193/A193M, A194/A194M, A320/A320M, F959/F959M, A449, A563, A563M, and F3125.  
1.2 The washers are designated by style denoting the shape, by type denoting the material, and by inch or metric dimensions.  
1.2.1 The styles of washers covered are:
1.2.1.1 Reaction—Circular washers with a knurled surface on one side and a contoured outside diameter designed to couple with the installation tool.
1.2.1.2 Backup—Circular washers having a knurled surface on both sides.  
1.2.2 The types of washers covered are:  
1.2.2.1 Type 1—Medium Carbon or Medium Carbon Alloy Steel.
1.2.2.2 Type 3—Weathering steel. This specification provides for furnishing Type 3 to chemical composition or a Corrosion Index (CRI) of 6 or higher, at the supplier’s option.  
1.3 The values stated in either inch-pound units for inch fasteners and SI units for metric fasteners and are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 14-Nov-2023
• ICS: 21.060.30 - Washers, locking elements
• Technical Committee: F16 - Fasteners
• Drafting Committee: F16.06 - Steel Washers and Rivets

Relations

• Replaces: ASTM F3394/F3394M-20 - Standard Specification for Hardened Steel Backup and Reaction Washers Inch and Metric Dimensions<rangeref></rangeref >
• Effective Date: 15-Nov-2023
• Refers: ASTM A320/A320M-24 - Standard Specification for Alloy-Steel and Stainless Steel Bolting for Low-Temperature Service
• Effective Date: 01-Mar-2024
• Refers: ASTM A193/A193M-24 - Standard Specification for Alloy-Steel and Stainless Steel Bolting for High Temperature or High Pressure Service and Other Special Purpose Applications
• Effective Date: 01-Mar-2024
• Refers: ASTM F1470-24 - Standard Practice for Fastener Sampling for Specified Mechanical Properties and Performance Inspection
• Effective Date: 01-Jan-2024
• Refers: ASTM A193/A193M-23 - Standard Specification for Alloy-Steel and Stainless Steel Bolting for High Temperature or High Pressure Service and Other Special Purpose Applications
• Effective Date: 01-Mar-2023
• Refers: ASTM A320/A320M-22a - Standard Specification for Alloy-Steel and Stainless Steel Bolting for Low-Temperature Service
• Effective Date: 01-Nov-2022
• Refers: ASTM F1470-19 - Standard Practice for Fastener Sampling for Specified Mechanical Properties and Performance Inspection
• Effective Date: 01-Aug-2019

Overview

ASTM F3394/F3394M-23: Standard Specification for Hardened Steel Backup and Reaction Washers Inch and Metric Dimensions defines the chemical, mechanical, and dimensional requirements for hardened steel backup and reaction washers to be used in conjunction with threaded fasteners. This international standard supports both inch and metric units, ensuring suitability for global projects in mechanical and structural applications.

Backup and reaction washers as described in this standard are essential components for fastener assemblies, providing improved load distribution and enhanced joint integrity. The washers are compatible with a wide range of fastener sizes, specifically for nominal diameters of 1/2 in. to 3 in. and M14 to M80, and are designed for use with bolts, nuts, studs, direct tension indicators (DTIs), and other fastener types, particularly those complying with ASTM fastener specifications such as A354, A193/A193M, A194/A194M, A320/A320M, F959/F959M, A449, A563, A563M, and F3125.

Key Topics

• Washer Styles and Types
  • Reaction Washers: Circular with a knurled surface on one side and a contoured outside diameter for installation tool engagement.
  • Backup Washers: Circular with a knurled surface on both sides.
  • Type 1: Medium carbon or medium carbon alloy steel.
  • Type 3: Weathering steel, supplied either to a defined chemical composition or a minimum Corrosion Resistance Index (CRI) of 6.
• Dimensional Requirements
  • Inch and metric dimensions detailed for a wide range of fastener sizes.
  • Specific tolerance limits for flatness, concentricity, and burrs.
• Mechanical Properties
  • All washers must be through-hardened with a Rockwell hardness of 38 to 45 HRC.
• Coatings and Finishes
  • Options include plain (unfinished), zinc-based coatings using thermodiffusion, mechanical deposition, zinc/aluminum corrosion protective coatings, and black oxide treatments.
  • Requirements for coating thickness, method, and marking are specified for traceability and performance.
• Traceability and Quality Assurance
  • Lot control and traceability are required throughout all manufacturing and processing operations.
  • Inspection and testing per lot assure conformance to chemical, mechanical, and coating criteria.

Applications

• Mechanical and Structural Fastening
  • Widely used in the assembly of steel structures, bridges, industrial machinery, and heavy equipment.
  • Essential for applications demanding high-strength fastening and reliable load transfer.
• Installation Procedures
  • The standard includes non-mandatory installation guidance for combined torque and angle, or turn-of-nut bolting methods, ensuring proper tensioning and long-term joint security.
• Compatibility
  • Suitable for use with other ASTM-specified fasteners, including high-strength bolts, nuts, and direct tension indicators.
• Corrosion Environments
  • Type 3 weathering steel washers provide enhanced resistance to atmospheric corrosion, ideal for outdoor or exposed structures.

Related Standards

• ASTM A193/A193M: Alloy-Steel and Stainless Steel Bolting for High Temperature or High Pressure Service.
• ASTM A194/A194M: Carbon, Alloy, and Stainless Steel Nuts for Bolts.
• ASTM A320/A320M: Alloy-Steel and Stainless Steel Bolting for Low-Temperature Service.
• ASTM F959/F959M: Compressible-Washer-Type Direct Tension Indicators.
• ASTM F1136/F1136M, A1059, B695, F3019, F2833, D769: Specifications for various protective coatings.
• ASTM A354, A449, A563, F3125: Specifications for bolts, nuts, and fastener assemblies.

Summary

ASTM F3394/F3394M-23 offers a comprehensive specification for hardened steel backup and reaction washers, ensuring mechanical strength, dimensional accuracy, reliable traceability, and diverse application suitability. By standardizing the requirements for these washers, ASTM supports secure, high-performance fastening in structural engineering and critical mechanical joints, with options to address both general and high-corrosion environments. This enhances both safety and efficiency in construction and manufacturing industries worldwide.

Keywords: hardened steel washers, ASTM F3394, backup washer, reaction washer, structural fastener washers, mechanical washers, inch metric washer dimensions, weathering steel washers, fastener coatings, ASTM standards

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F3394/F3394M − 23
Standard Specification for
Hardened Steel Backup and Reaction Washers Inch and
1,2
Metric Dimensions
This standard is issued under the fixed designation F3394/F3394M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope shall be used independently of the other. Combining values
from the two systems may result in non-conformance with the
1.1 This specification covers the chemical, mechanical, and
standard.
dimensional requirements for hardened steel Backup and
1.4 This standard does not purport to address all of the
Reaction washers for use with fasteners having nominal
safety concerns, if any, associated with its use. It is the
diameters of ⁄2 in. through 3 in. and M14 through M80. These
responsibility of the user of this standard to establish appro-
washers are intended for general-purpose mechanical and
priate safety, health, and environmental practices and deter-
structural use with bolts, nuts, studs, DTIs, and other internally
mine the applicability of regulatory limitations prior to use.
and externally threaded fasteners. These washers are suitable
1.5 This international standard was developed in accor-
for use with fasteners covered in Specifications A354, A193/
dance with internationally recognized principles on standard-
A193M, A194/A194M, A320/A320M, F959/F959M, A449,
ization established in the Decision on Principles for the
A563, A563M, and F3125.
Development of International Standards, Guides and Recom-
1.2 The washers are designated by style denoting the shape,
mendations issued by the World Trade Organization Technical
by type denoting the material, and by inch or metric dimen-
Barriers to Trade (TBT) Committee.
sions.
1.2.1 The styles of washers covered are:
2. Referenced Documents
1.2.1.1 Reaction—Circular washers with a knurled surface
2.1 ASTM Standards:
on one side and a contoured outside diameter designed to
A193/A193M Specification for Alloy-Steel and Stainless
couple with the installation tool.
Steel Bolting for High Temperature or High Pressure
1.2.1.2 Backup—Circular washers having a knurled surface
Service and Other Special Purpose Applications
on both sides.
A194/A194M Specification for Carbon Steel, Alloy Steel,
1.2.2 The types of washers covered are:
and Stainless Steel Nuts for Bolts for High Pressure or
1.2.2.1 Type 1—Medium Carbon or Medium Carbon Alloy
High Temperature Service, or Both
Steel.
A320/A320M Specification for Alloy-Steel and Stainless
1.2.2.2 Type 3—Weathering steel. This specification pro-
Steel Bolting for Low-Temperature Service
vides for furnishing Type 3 to chemical composition or a
A354 Specification for Quenched and Tempered Alloy Steel
Corrosion Index (CRI) of 6 or higher, at the supplier’s option.
Bolts, Studs, and Other Externally Threaded Fasteners
A449 Specification for Hex Cap Screws, Bolts and Studs,
1.3 The values stated in either inch-pound units for inch
Steel, Heat Treated, 120/105/90 ksi Minimum Tensile
fasteners and SI units for metric fasteners and are to be
Strength, General Use
regarded separately as standard. The values stated in each
A563 Specification for Carbon and Alloy Steel Nuts
system may not be exact equivalents; therefore, each system
A563M Specification for Carbon and Alloy Steel Nuts (Met-
ric) (Withdrawn 2021)
A588/A588M Specification for High-Strength Low-Alloy
This specification is under the jurisdiction of ASTM Committee F16 on
Structural Steel, up to 50 ksi [345 MPa] Minimum Yield
Fasteners and is the direct responsibility of Subcommittee F16.06 on Steel Washers
Point, with Atmospheric Corrosion Resistance
and Rivets.
Current edition approved Nov. 15, 2023. Published November 2023. Originally
approved in 2020. Last previous edition approved in 2020 as F3394/F3394M – 20.
DOI: 10.1520/F3394-23. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Backup and Reaction washers of the type covered by this standard have a patent contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
application pending. Interested parties are invited to submit information regarding Standards volume information, refer to the standard’s Document Summary page on
the identification of an alternative(s) to these patent-pending items to the ASTM the ASTM website.
International Headquarters. Your comments will receive careful consideration at a The last approved version of this historical standard is referenced on
meeting of the responsible technical committee, which you may attend www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3394/F3394M − 23
A751 Test Methods and Practices for Chemical Analysis of 5. Materials and Manufacture
Steel Products
5.1 Steel used in the manufacture of Reaction and Backup
A1059 Specification for Zinc Alloy Thermo-Diffusion Coat-
washers shall be produced by the open-hearth, basic-oxygen, or
ings (TDC) on Steel Fasteners, Hardware, and Other
electric-furnace process.
Products
5.2 Backup and Reaction Washers shall be through-
B695 Specification for Coatings of Zinc Mechanically De-
hardened by heating to a temperature above the upper trans-
posited on Iron and Steel
formation temperature, quenching in a liquid medium, and
D769 Specification for Black Synthetic Iron Oxide
tempering by reheating to not less than 800 °F ⁄427 °C. Alloy
F606/F606M Test Methods for Determining the Mechanical
steel washers shall be quenched in oil.
Properties of Externally and Internally Threaded
Fasteners, Washers, Direct Tension Indicators, and Rivets
5.3 Protective Coatings:
F959/F959M Specification for Compressible-Washer-Type
5.3.1 Unless otherwise specified, washers shall be fur-
Direct Tension Indicators for Use with Structural
nished “plain” with the “as-fabricated” surface finish without
Fasteners, Inch and Metric Series
protective coatings.
F1136/F1136M Specification for Zinc/Aluminum Corrosion
5.3.2 When zinc-coated washers are required, the purchaser
Protective Coatings for Fasteners
shall specify the zinc coating process, for example,
F1470 Practice for Fastener Sampling for Specified Me-
thermodiffusion, mechanically deposited, Zinc/Aluminum Cor-
chanical Properties and Performance Inspection
rosion Protective Coating, or no preference.
F1789 Terminology for F16 Mechanical Fasteners
5.3.2.1 When thermo-diffusion is specified the washers shall
F2833 Specification for Corrosion Protective Fastener Coat-
be zinc coated by the thermo-diffusion process in accordance
ings with Zinc Rich Base Coat and Aluminum Organic/
with the requirements of Class 25 of Specification A1059.
Inorganic Type
5.3.2.2 When mechanically deposited is specified the wash-
F3019 Specification for Chromium Free Zinc-Flake
ers shall be zinc coated by the mechanical-deposition process
Composite, with or without Integral Lubricant, Corrosion
in accordance with the requirements of Class 55 of Specifica-
Protective Coatings for Fasteners
tion B695.
F3125 Specification for High Strength Structural Bolts and
5.3.2.3 When Zinc/Aluminum Corrosion Protective Coating
Assemblies, Steel and Alloy Steel, Heat Treated, Inch
is specified, the washers shall be coated in accordance with the
Dimensions 120 ksi and 150 ksi Minimum Tensile
requirements of Grade 3 of Specification F1136/F1136M,
Strength, and Metric Dimensions 830 MPa and 1040 MPa
Grade 1 of Specification F2833, or Grade 4 of Specification
Minimum Tensile Strength
F3019.
G101 Guide for Estimating the Atmospheric Corrosion Re-
5.3.3 When black oxide is specified the washers shall be
sistance of Low-Alloy Steels
black oxide treated in accordance with the requirements of
2.2 ISO Standards:
Specification D769 or ISO 11408.
ISO 11408 Chemical conversion coatings — Black oxide
5.3.4 Other coatings or surface finishes are to be used only
coating on iron and steel — Specification and test methods
when approved by the manufacturer.
5.4 Secondary Processing:
3. Terminology
5.4.1 Lot control and full traceability shall be maintained
3.1 Terms used in this specification are defined in Termi-
throughout all outside and secondary processes.
nology F1789 unless otherwise defined herein.
5.4.2 If washers are heat-treated or coated by a
subcontractor, they shall be returned to the manufacturer for
4. Ordering Information
testing prior to shipment to the purchaser.
4.1 Orders under this specification shall include the follow-
6. Chemical Composition
ing:
4.1.1 Quantity (number of pieces),
6.1 Type 1 washers shall conform to the chemical compo-
4.1.2 Style (Reaction Washer, Backup Washer, see 1.2.1),
sition specified in Table 1.
4.1.3 Type (see 1.2.2),
6.2 Type 3 washers shall conform to the heat analysis
4.1.4 Size, that is, nominal diameter,
specified in Table 1.
4.1.5 ASTM designation and year of issue (if not specified,
6.2.1 Alternatively, at the supplier’s option, Type 3 washers
current issue shall be used),
having a Copper minimum Heat Analysis of 0.25 %, Phospho-
4.1.6 Coating type, if required (see 5.3),
rous and Sulfur conforming to Table 1 and a Corrosion Index
4.1.7 Source inspection, if required (see Section 12),
of 6 or higher as calculated from the Heat Analysis as described
4.1.8 Test reports, if required (see Section 14), and
in Guide G101 Predictive method based on the data of Larabee
4.1.9 Any special requirements.
and Coburn, or the predictive method based upon the data of
Townsend, shall be accepted.
6.2.2 Product Analysis are not applicable to Type 3 washers
Available from International Organization for Standardization (ISO), ISO
furnished to a CRI of 6 or higher calculated from the Heat
Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,
Geneva, Switzerland, http://www.iso.org. Analysis.
F3394/F3394M − 23
A
TABLE 1 Chemical Requirements
7. Mechanical Properties
Composition
Element 7.1 All Backup and Reaction Washers shall be through-
B C
Type 1 Type 3
hardened to a hardness of 38 to 45 HRC.
Carbon
Heat analysis 0.30 – 0.57 0.30 – 0.57
Product analysis 0.28 – 0.59 0.28 – 0.59 8. Dimensions and Tolerances
Phosphorus, max
8.1 Reaction washers, as shown in Fig. 1, shall conform to
Heat analysis 0.040 0.040
Product analysis 0.050 0.045
the dimensions shown in Table 2 (inch series washers) or Table
Sulfur, max
3 (metric series washers). Backup washers, as shown in Fig. 2,
Heat analysis 0.050 0.050
shall conform to the dimensions shown in Table 4 (inch series
Product analysis 0.060 0.055
Silicon
washers) and Table 5 (metric series washers).
Heat analysis . 0.15–0.35
8.1.1 Contoured Outside Diameter—The outer edge located
Product analysis . 0.13–0.37
Chromium between the Bearing Diameter (BD) and the Outside Diameter
Heat analysis . 0.45–0.65
(OD) shall be designed to couple with the reaction surface of
Product analysis . 0.42–0.68
the installation tool. For washers having an odd number of
Nickel
Heat analysis . 0.25–0.45 projections, the Outside Diameter shall be the diameter of the
Product analysis . 0.22–0.48
circle scribed such that it traverses through the peaks of the
Copper
projections.
Heat analysis . 0.25–0.45
Product analysis . 0.22–0.48 8.1.2 Knurled Surfaces:
A
8.1.2.1 Knurls shall be located between the Inside Diameter
When providing Weathering Steels to a calculated corrosion index use the
Legault-Leckie formula from Guide G101. Link to online calculator: http://
(ID) and the Bearing Diameter (BD) on Reaction Washers.
www.astm.org/COMMIT/G01_G101Calcultr1100.xls
8.1.2.2 Knurls shall be located between the Inside Diameter
I = 26.01 (% Cu) + 3.88 (% Ni) + (% Cr)
+ 1.49 (% Si) + 17.28 (% P) – 7.29 (% Cu) (% Ni) (ID) and the Outside Diameter (OD) on Backup Washers.
–9.10 (% Ni) (% P) – 33.39 (% Cu)
8.1.2.3 The maximum spacing between knurls shall be 0.1
B
Steel, as defined by the American Iron and Steel Institute, shall be considered to
in. for inch-series washers and 2.5 mm for metric-series
be alloy when the maximum range given for the content of alloying elements
exceeds one or more of the following limits: Manganese, 1.65 %; silicon, 0.60 %;
washers.
copper, 0.60 % or in which a definite range or a definite minimum quantity of any
8.1.2.4 The minimum height for knurls is 0.005 in. for
of the following elements is specified or required within the limits of the recognized
inch-series washers and 0.125 mm for metric-series washers.
field of constructional alloy steels: aluminum, chromium up to 3.99 %, cobalt,
columbium, molybdenum, nickel, titanium, tungsten, vanadium, zirconium, or any
8.1.2.5 The maximum height for knurls shall be included in
other alloying elements added to obtain a desired alloying effect.
the determination of the overall thickness (T).
C
Weathering steel washers may also be manufactured from any of the steels
8.1.3 Flatness, Concentricity, and Burrs—Tolerances for
listed in Table 2 of Specifications A588/A588M and F3125.
flatness, concentricity, and burrs shall be in accordance with
Table 6.
8.1.4 All dimensions are as-formed, prior to the application
of coating or plating, or both.
6.3 For Type 1 and Type 3 washers furnished to the
Chemical Compositions in Table 1, Product Analysis of fin-
ished washers representing each lot shall conform to the 9. Workmanship, Finish, and Appearance
requirements for Chemical Composition in Table 1, Product
9.1 The washers shall be free of injurious material or
Analysis.
manufacturing defects that would affect their performance. All
washers shall be free of excessive burrs and sharp edges. (see
6.4 Chemical analyses shall be performed in accordance
with Test Methods, Practices, and Terminology A751. Table 6).
FIG. 1 Reaction Washer
F3394/F3394M − 23
TABLE 2 Reaction Washer Dimensions (Inch Series)
A
Inside Diameter (ID) Outside Diameter (OD) Thickness (T) Bearing Diameter (BD)
Inches
Nominal Inches Inches Inches
min max min max min max min max
⁄2 0.520 0.600 1.00 1.20 0.097 0.180 0.90 1.10
⁄16 0.585 0.700 1.10 1.30 0.110 0.180 1.00 1.20
⁄8 0.651 0.800 1.30 1.50 0.122 0.180 1.10 1.30
⁄4 0.783 0.900 1.50 1.70 0.122 0.220 1.30 1.50
⁄8 0.914 1.000 1.70 2.00 0.136 0.220 1.50 1.70
1 1.043 1.200 1.90 2.20 0.136 0.220 1.70 1.90
1 ⁄8 1.174 1.400 2.20 2.50 0.158 0.260 2.00 2.30
1 ⁄4 1.306 1.500 2.40 2.70 0.158 0.260 2.10 2.40
1 ⁄8 1.437 1.600 2.60 2.90 0.158 0.260 2.30 2.60
1 ⁄2 1.568 1.700 2.80 3.10 0.158 0.260 2.50 2.80
1 ⁄8 1.693 1.800 3.00 3.30 0.158 0.320 2.70 3.00
1 ⁄4 1.818 1.900 3.30 3.60 0.178 0.320 3.00 3.30
1 ⁄8 1.943 2.100 3.60 3.80 0.178 0.320 3.20 3.50
2 2.068 2.300 3.70 4.00 0.178 0.320 3.30 3.70
2 ⁄4 2.318 2.500 4.20 4.50 0.240 0.400 3.80 4.20
2 ⁄2 2.568 2.800 4.60 4.90 0.240 0.430 4.20 4.60
2 ⁄4 2.818 3.000 5.10 5.40 0.240 0.430 4.60 5.00
3 3.068 3.300 5.40 5.70 0.240 0.500 5.00 5.40
A
The referee method for determination of inside diameter shall be use of go/no-go plug gauges of class XX or better.
TABLE 3 Reaction Washer Dimensions (Metric Series)
A
Inside Diameter (ID) Outside Diameter (OD) Thickness (T) Bearing Diameter (BD)
Millimeters
Millimeters Millimeters Millimeters
Nominal
min max min max min max min max
M14 14.50 17.00 27.0 30.0 3.1 4.0 24.0 27.0
M16 16.50 19.00 30.0 33.0 3.1 4.0 26.0 29.0
M18 18.50 21.00 35.0 38.0 3.1 4.0 29.0 32.0
M20 20.50 23.00 36.0 39.0 3.1 4.0 32.0 35.0
M22 23.00 26.00 39.0 42.0 3.4 4.0 35.0 38.0
M24 25.00 28.00 45.0 48.0 3.4 5.0 40.0 44.0
M27 28.00 31.00 50.0 53.0 4.0 5.0 44.0 48.0
M30 31.00 34.00 56.0 59.0 4.0 6.0 51.0 55.0
M33 34.00 37.00 61.0 64.0 4.0 7.0 54.0 58.0
M36 37.00 40.00 67.0 70.0 4.0 7.0 60.0 64.0
M39 40.00 43.00 72.0 75.0 4.0 7.0 65.0 69.0
M42 43.00 46.00 78.0 82.0 4.6 8.0 71.0 76.0
M45 46.00 49.00 83.0 87.0 4.6 8.0 77.0 82.0
M48 49.00 52.00 90.0 94.0 4.6 8.0 83.0 88.0
M52 53.00 56.00 94.0 98.0 4.6 8.0 87.0 92.0
M56 57.00 61.00 106.0 110.0 6.1 9.0 98.0 103.0
M60 61.00 66.00 106.0 110.0 6.1 9.0 98.0 103.0
M64 65.00 70.00 118.0 122.0 6.1 11.0 108.0 113.0
M68 69.00 74.00 118.0 122.0 6.1 11.0 108.0 113.0
M72 73.00 78.00 130.0 134.0 6.1 11.0 118.0 123.0
M76 77.00 82.00 130.0 134.0 6.1 11.0 118.0 123.0
M80 81.00 86.00 138.0 144.0 6.1 14.0 126.0 132.0
A
The referee method for determination of inside diameter shall be use of go/no-go plug gauges of class XX or better
10. Number of Test and Retests integrity of each production lot of washers from raw material
selection through all processing operations and treatments to
10.1 Responsibility:
final packing and shipment. Each lot shall be assigned its own
10.1.1 The manufacturer shall inspect and test each lot of
lot identification number, each lot shall be inspected and tested,
washers prior to shipment in accordance with the lot control/
and the inspection and test reports for each lot shall be retained.
quality assurance procedures described in 10.2 through 10.4.
10.1.2 When supplied by a source other than the manufac-
10.2.2 The minimum number of samples to be tested to
turer or processed by an outside supplier, the responsible party
determine hardness and coating thickness (when applicable)
shall ensure that all tests have been performed and the washers
shall be in accordance with the requirements specified in Guide
conform to this specification.
F1470.
10.2 Production Lot Method:
10.3 Number of Tests After Alterations—If washers are
10.2.1 All Reaction and Backup washers shall be processed
heat-treated, coated, or otherwise altered by a subcontractor or
in accordance with a lot identification
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F3394/F3394M − 20 F3394/F3394M − 23
Standard Specification for
Hardened Steel Backup and Reaction Washers Inch and
1,2
Metric Dimensions
This standard is issued under the fixed designation F3394/F3394M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This specification covers the chemical, mechanical, and dimensional requirements for hardened steel Backup and Reaction
washers for use with fasteners having nominal diameters of ⁄2 in. through 3 in. and M14 through M80. These washers are intended
for general-purpose mechanical and structural use with bolts, nuts, studs, DTIs, and other internally and externally threaded
fasteners. These washers are suitable for use with fasteners covered in Specifications A354, A193/A193M, A194/A194M,
A320/A320M, F959/F959M, A449, A563, A563M, and F3125.
1.2 The washers are designated by style denoting the shape, by type denoting the material, and by inch or metric dimensions.
1.2.1 The styles of washers covered are:
1.2.1.1 Reaction—Circular washers with a knurled surface on one side and a contoured outside diameter designed to couple with
the installation tool.
1.2.1.2 Backup—Circular washers having a knurled surface on both sides.
1.2.2 The types of washers covered are:
1.2.2.1 Type 1—Medium Carbon or Medium Carbon Alloy Steel.
1.2.2.2 Type 3—Weathering steel. This specification provides for furnishing Type 3 to chemical composition or a Corrosion Index
(CRI) of 6 or higher, at the supplier’s option.
1.3 The values stated in either inch-pound units for inch fasteners and SI units for metric fasteners and are to be regarded
separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used
independently of the other. Combining values from the two systems may result in non-conformance with the standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
This specification is under the jurisdiction of ASTM Committee F16 on Fasteners and is the direct responsibility of Subcommittee F16.06 on Steel Washers and Rivets.
Current edition approved Jan. 1, 2020Nov. 15, 2023. Published March 2020November 2023. Originally approved in 2020. Last previous edition approved in 2020 as
F3394/F3394M – 20. DOI: 10.1520/F3394–2010.1520/F3394-23.
Backup and Reaction washers of the type covered by this standard have a patent application pending. Interested parties are invited to submit information regarding the
identification of an alternative(s) to these patent-pending items to the ASTM International Headquarters. Your comments will receive careful consideration at a meeting of
the responsible technical committee, which you may attend
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3394/F3394M − 23
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
A193/A193M Specification for Alloy-Steel and Stainless Steel Bolting for High Temperature or High Pressure Service and Other
Special Purpose Applications
A194/A194M Specification for Carbon Steel, Alloy Steel, and Stainless Steel Nuts for Bolts for High Pressure or High
Temperature Service, or Both
A320/A320M Specification for Alloy-Steel and Stainless Steel Bolting for Low-Temperature Service
A354 Specification for Quenched and Tempered Alloy Steel Bolts, Studs, and Other Externally Threaded Fasteners
A449 Specification for Hex Cap Screws, Bolts and Studs, Steel, Heat Treated, 120/105/90 ksi Minimum Tensile Strength,
General Use
A563 Specification for Carbon and Alloy Steel Nuts
A563M Specification for Carbon and Alloy Steel Nuts (Metric) (Withdrawn 2021)
A588/A588M Specification for High-Strength Low-Alloy Structural Steel, up to 50 ksi [345 MPa] Minimum Yield Point, with
Atmospheric Corrosion Resistance
A751 Test Methods and Practices for Chemical Analysis of Steel Products
A1059 Specification for Zinc Alloy Thermo-Diffusion Coatings (TDC) on Steel Fasteners, Hardware, and Other Products
B695 Specification for Coatings of Zinc Mechanically Deposited on Iron and Steel
D769 Specification for Black Synthetic Iron Oxide
F606/F606M Test Methods for Determining the Mechanical Properties of Externally and Internally Threaded Fasteners,
Washers, Direct Tension Indicators, and Rivets
F959/F959M Specification for Compressible-Washer-Type Direct Tension Indicators for Use with Structural Fasteners, Inch and
Metric Series
F1136/F1136M Specification for Zinc/Aluminum Corrosion Protective Coatings for Fasteners
F1470 Practice for Fastener Sampling for Specified Mechanical Properties and Performance Inspection
F1789 Terminology for F16 Mechanical Fasteners
F2833 Specification for Corrosion Protective Fastener Coatings with Zinc Rich Base Coat and Aluminum Organic/Inorganic
Type
F3019 Specification for Chromium Free Zinc-Flake Composite, with or without Integral Lubricant, Corrosion Protective
Coatings for Fasteners
F3125 Specification for High Strength Structural Bolts and Assemblies, Steel and Alloy Steel, Heat Treated, Inch Dimensions
120 ksi and 150 ksi Minimum Tensile Strength, and Metric Dimensions 830 MPa and 1040 MPa Minimum Tensile Strength
G101 Guide for Estimating the Atmospheric Corrosion Resistance of Low-Alloy Steels
2.2 ISO Standards:
ISO 11408 Chemical conversion coatings — Black oxide coating on iron and steel — Specification and test methods
3. Terminology
3.1 Terms used in this specification are defined in Terminology F1789 unless otherwise defined herein.
4. Ordering Information
4.1 Orders under this specification shall include the following:
4.1.1 Quantity (number of pieces),
4.1.2 Style (Reaction Washer, Backup Washer, see 1.2.1),
4.1.3 Type (see 1.2.2),
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Available from International Organization for Standardization (ISO), ISO Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
Switzerland, http://www.iso.org.
F3394/F3394M − 23
4.1.4 Size, that is, nominal diameter,
4.1.5 ASTM designation and year of issue (if not specified, current issue shall be used),
4.1.6 Coating type, if required (see 5.3),
4.1.7 Source inspection, if required (see Section 12),
4.1.8 Test reports, if required (see Section 14), and
4.1.9 Any special requirements.
5. Materials and Manufacture
5.1 Steel used in the manufacture of Reaction and Backup washers shall be produced by the open-hearth, basic-oxygen, or
electric-furnace process.
5.2 Backup and Reaction Washers shall be through-hardened by heating to a temperature above the upper transformation
temperature, quenching in a liquid medium, and tempering by reheating to not less than 800 °F ⁄427 °C. Alloy steel washers shall
be quenched in oil.
5.3 Protective Coatings:
5.3.1 Unless otherwise specified, washers shall be furnished “plain” with the “as-fabricated” surface finish without protective
coatings.
5.3.2 When zinc-coated washers are required, the purchaser shall specify the zinc coating process, for example, thermodiffusion,
mechanically deposited, Zinc/Aluminum Corrosion Protective Coating, or no preference.
5.3.2.1 When thermo-diffusion is specified the washers shall be zinc coated by the thermo-diffusion process in accordance with
the requirements of Class 25 of Specification A1059.
5.3.2.2 When mechanically deposited is specified the washers shall be zinc coated by the mechanical-deposition process in
accordance with the requirements of Class 55 of Specification B695.
5.3.2.3 When Zinc/Aluminum Corrosion Protective Coating is specified, the washers shall be coated in accordance with the
requirements of Grade 3 of Specification F1136/F1136M, Grade 1 of Specification F2833, or Grade 4 of Specification F3019.
5.3.3 When black oxide is specified the washers shall be black oxide treated in accordance with the requirements of Specification
D769 or ISO 11408.
5.3.4 Other coatings or surface finishes are to be used only when approved by the manufacturer.
5.4 Secondary Processing:
5.4.1 Lot control and full traceability shall be maintained throughout all outside and secondary processes.
5.4.2 If washers are heat-treated or coated by a subcontractor, they shall be returned to the manufacturer for testing prior to
shipment to the purchaser.
6. Chemical Composition
6.1 Type 1 washers shall conform to the chemical composition specified in Table 1.
6.2 Type 3 washers shall conform to the heat analysis specified in Table 1.
F3394/F3394M − 23
A
TABLE 1 Chemical Requirements
Composition
Element
B C
Type 1 Type 3
Carbon
Heat analysis 0.30 – 0.57 0.30 – 0.57
Product analysis 0.28 – 0.59 0.28 – 0.59
Phosphorus, max
Heat analysis 0.040 0.040
Product analysis 0.050 0.045
Sulfur, max
Heat analysis 0.050 0.050
Product analysis 0.060 0.055
Silicon
Heat analysis . 0.15–0.35
Product analysis . 0.13–0.37
Chromium
Heat analysis . 0.45–0.65
Product analysis . 0.42–0.68
Nickel
Heat analysis . 0.25–0.45
Product analysis . 0.22–0.48
Copper
Heat analysis . 0.25–0.45
Product analysis . 0.22–0.48
A
When providing Weathering Steels to a calculated corrosion index use the
Legault-Leckie formula from Guide G101. Link to online calculator: http://
www.astm.org/COMMIT/G01_G101Calcultr1100.xls
I = 26.01 (% Cu) + 3.88 (% Ni) + (% Cr)
+ 1.49 (% Si) + 17.28 (% P) – 7.29 (% Cu) (% Ni)
–9.10 (% Ni) (% P) – 33.39 (% Cu)
B
Steel, as defined by the American Iron and Steel Institute, shall be considered to
be alloy when the maximum range given for the content of alloying elements
exceeds one or more of the following limits: Manganese, 1.65 %; silicon, 0.60 %;
copper, 0.60 % or in which a definite range or a definite minimum quantity of any
of the following elements is specified or required within the limits of the recognized
field of constructional alloy steels: aluminum, chromium up to 3.99 %, cobalt,
columbium, molybdenum, nickel, titanium, tungsten, vanadium, zirconium, or any
other alloying elements added to obtain a desired alloying effect.
C
Weathering steel washers may also be manufactured from any of the steels
listed in Table 2 of Specifications A588/A588M and F3125.
6.2.1 Alternatively, at the supplier’s option, Type 3 washers having a Copper minimum Heat Analysis of 0.25 %, Phosphorous and
Sulfur conforming to Table 1 and a Corrosion Index of 6 or higher as calculated from the Heat Analysis as described in Guide G101
Predictive method based on the data of Larabee and Coburn, or the predictive method based upon the data of Townsend, shall be
accepted.
6.2.2 Product Analysis are not applicable to Type 3 washers furnished to a CRI of 6 or higher calculated from the Heat Analysis.
6.3 For Type 1 and Type 3 washers furnished to the Chemical Compositions in Table 1, Product Analysis of finished washers
representing each lot shall conform to the requirements for Chemical Composition in Table 1, Product Analysis.
6.4 Chemical analyses shall be performed in accordance with Test Methods, Practices, and Terminology A751.
7. Mechanical Properties
7.1 All Backup and Reaction Washers shall be through-hardened to a hardness of 38 to 45 HRC.
8. Dimensions and Tolerances
8.1 Reaction washers, as shown in Fig. 1, shall conform to the dimensions shown in Table 2 (inch series washers) or Table 3
(metric series washers). Backup washers, as shown in Fig. 2, shall conform to the dimensions shown in Table 4 (inch series
washers) and Table 5 (metric series washers).
8.1.1 Contoured Outside Diameter—The outer edge located between the Bearing Diameter (BD) and the Outside Diameter (OD)
F3394/F3394M − 23
FIG. 1 Reaction Washer
TABLE 2 Reaction Washer Dimensions (Inch Series)
A
Inside Diameter (ID) Outside Diameter (OD) Thickness (T) Bearing Diameter (BD)
Inches
Nominal Inches Inches Inches
min max min max min max min max
⁄2 0.520 0.600 1.00 1.20 0.097 0.180 0.90 1.10
⁄16 0.585 0.700 1.10 1.30 0.110 0.180 1.00 1.20
⁄8 0.651 0.800 1.30 1.50 0.122 0.180 1.10 1.30
⁄4 0.783 0.900 1.50 1.70 0.122 0.220 1.30 1.50
⁄8 0.914 1.000 1.70 2.00 0.136 0.220 1.50 1.70
1 1.043 1.200 1.90 2.20 0.136 0.220 1.70 1.90
1 ⁄8 1.174 1.400 2.20 2.50 0.158 0.260 2.00 2.30
1 ⁄4 1.306 1.500 2.40 2.70 0.158 0.260 2.10 2.40
1 ⁄8 1.437 1.600 2.60 2.90 0.158 0.260 2.30 2.60
1 ⁄2 1.568 1.700 2.80 3.10 0.158 0.260 2.50 2.80
1 ⁄8 1.693 1.800 3.00 3.30 0.158 0.320 2.70 3.00
1 ⁄4 1.818 1.900 3.30 3.60 0.178 0.320 3.00 3.30
1 ⁄8 1.943 2.100 3.60 3.80 0.178 0.320 3.20 3.50
2 2.068 2.300 3.70 4.00 0.178 0.320 3.30 3.70
2 ⁄4 2.318 2.500 4.20 4.50 0.240 0.400 3.80 4.20
2 ⁄2 2.568 2.800 4.60 4.90 0.240 0.430 4.20 4.60
2 ⁄4 2.818 3.000 5.10 5.40 0.240 0.430 4.60 5.00
3 3.068 3.300 5.40 5.70 0.240 0.500 5.00 5.40
A
The referee method for determination of inside diameter shall be use of go/no-go plug gauges of class XX or better.
shall be designed to couple with the reaction surface of the installation tool. For washers having an odd number of projections,
the Outside Diameter shall be the diameter of the circle scribed such that it traverses through the peaks of the projections.
8.1.2 Knurled Surfaces:
8.1.2.1 Knurls shall be located between the Inside Diameter (ID) and the Bearing Diameter (BD) on Reaction Washers.
8.1.2.2 Knurls shall be located between the Inside Diameter (ID) and the Outside Diameter (OD) on Backup Washers.
8.1.2.3 The maximum spacing between knurls shall be 0.1 in. for inch-series washers and 2.5 mm for metric-series washers.
8.1.2.4 The minimum height for knurls is 0.005 in. for inch-series washers and 0.125 mm for metric-series washers.
8.1.2.5 The maximum height for knurls shall be included in the determination of the overall thickness (T).
8.1.3 Flatness, Concentricity, and Burrs—Tolerances for flatness, concentricity, and burrs shall be in accordance with Table 6.
8.1.4 All dimensions are as-formed, prior to the application of coating or plating, or both.
9. Workmanship, Finish, and Appearance
9.1 The washers shall be free of injurious material or manufacturing defects that would affect their performance. All washers shall
be free of excessive burrs and sharp edges. (see Table 6).
F3394/F3394M − 23
TABLE 3 Reaction Washer Dimensions (Metric Series)
A
Inside Diameter (ID) Outside Diameter (OD) Thickness (T) Bearing Diameter (BD)
Millimeters
Millimeters Millimeters Millimeters
Nominal
min max min max min max min max
M14 14.50 17.00 27.0 30.0 3.1 4.0 24.0 27.0
M16 16.50 19.00 30.0 33.0 3.1 4.0 26.0 29.0
M18 18.50 21.00 35.0 38.0 3.1 4.0 29.0 32.0
M20 20.50 23.00 36.0 39.0 3.1 4.0 32.0 35.0
M22 23.00 26.00 39.0 42.0 3.4 4.0 35.0 38.0
M24 25.00 28.00 45.0 48.0 3.4 5.0 40.0 44.0
M27 28.00 31.00 50.0 53.0 4.0 5.0 44.0 48.0
M30 31.00 34.00 56.0 59.0 4.0 6.0 51.0 55.0
M33 34.00 37.00 61.0 64.0 4.0 7.0 54.0 58.0
M36 37.00 40.00 67.0 70.0 4.0 7.0 60.0 64.0
M39 40.00 43.00 72.0 75.0 4.0 7.0 65.0 69.0
M42 43.00 46.00 78.0 82.0 4.6 8.0 71.0 76.0
M45 46.00 49.00 83.0 87.0 4.6 8.0 77.0 82.0
M48 49.00 52.00 90.0 94.0 4.6 8.0 83.0 88.0
M52 53.00 56.00 94.0 98.0 4.6 8.0 87.0 92.0
M56 57.00 61.00 106.0 110.0 6.1 9.0 98.0 103.0
M60 61.00 66.00 106.0 110.0 6.1 9.0 98.0 103.0
M64 65.00 70.00 118.0 122.0 6.1 11.0 108.0 113.0
M68 69.00 74.00 118.0 122.0 6.1 11.0 108.0 113.0
M72 73.00 78.00 130.0 134.0 6.1 11.0 118.0 123.0
M76 77.00 82.00 130.0 134.0 6.1 11.0 118.0 123.0
M80 81.00 86.00 138.0 144.0 6.1 14.0 126.0 132.0
A
The referee method for determination of inside diameter shall be use of go/no-go plug gauges of class XX or better
FIG. 2 Backup Washer
10. Number of Test and Retests
10.1 Responsibility:
10.1.1 The manufacturer shall inspect and test each lot of washers prior to shipment in accordance with the lot control/quality
assurance procedures described in 10.2 through 10.4.
10.1.2 When supplied by a source other than the manufacturer or processed by an outside supplier, the responsible party shall
ensure that all tests have been performed and the washers conform to this specification.
10.2 Production Lot Method:
10.2.1 All Reaction and Backup washers shall be processed in accordance with a lot identification control—quality assurance plan.
The manufacturer shall identify and maintain the integrity of each production lot of washers from raw material selection through
all processing operations and treatments to final packing and shipment. Each lot shall be assigned its own lot identification number,
each lot shall be inspected and tested, and the inspection and test reports for each lot shall be retained.
F3394/F3394M − 23
TABLE 4 Backup Washer Dimensions (Inch Series)
A
I
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