Fastener Standards | ASTM, DIN, ISO, ASME, BS | HITECH Fastener
Fastener Standards Reference — ASTM · DIN · ISO · ASME · BS · JIS · EN
Global Standards Reference Guide

Fastener
Standards

ASTM · DIN · ISO · ASME · BS · JIS · EN — All in One Place

A comprehensive technical reference for international fastener standards. Covering dimensional, material, mechanical, and testing specifications for bolts, nuts, screws, washers, studs, and threaded rods — designed for global procurement engineers and project teams.

8+
Standards Bodies
200+
Individual Standards
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Standards Overview

Why Fastener Standards Matter

International standards ensure dimensional interchangeability, mechanical performance, and material traceability across global supply chains.

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Dimensional Standards

Define exact geometry: head dimensions, shank diameter, thread pitch, grip length, washer face, and bearing surface. Critical for interchangeability between suppliers and OEM assemblies.

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Mechanical Standards

Prescribe minimum yield strength, tensile strength, hardness, proof load, and elongation. Organised into property classes (metric) or grade markings (imperial) on bolt heads.

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Material Standards

Specify alloy composition ranges, heat treatment conditions, and microstructural requirements for carbon steel, alloy steel, stainless steel, and non-ferrous fastener materials.

Standards Bodies at a Glance

ASTM International

American Society for Testing and Materials

Predominant in North America and oil & gas globally. Covers material grades, mechanical property testing, and dimensional tolerances through hundreds of individual standards (A193, A320, F3125, etc.).

A193A194A307A325A490F593F3125

DIN / DIN EN

Deutsches Institut für Normung

German national standards widely used across Europe, automotive OEMs, and precision machinery. Many DIN standards have been superseded by harmonised EN ISO standards but remain specified by legacy customers.

DIN 931DIN 933DIN 934DIN 976DIN 7991DIN 6923

ISO

International Organization for Standardization

The universal international standard adopted by 167 countries. ISO fastener standards define metric thread profiles, property classes (8.8, 10.9, A2-70), dimensional tolerances, and test methods globally accepted.

ISO 4014ISO 4032ISO 898-1ISO 3506ISO 4759ISO 4017

ASME

American Society of Mechanical Engineers

Mandatory for pressure vessel, piping, and power plant bolting worldwide. ASME B18 series covers dimensional standards; SA-prefixed material standards mirror ASTM with additional PV code requirements.

B18.2.1B18.2.2SA193SA194SA320B16.5
American Standards

ASTM Standards — Detailed Reference

ASTM

A193 — Alloy-Steel & Stainless Steel Bolting for High Temp / High Pressure

Stud bolts, headed bolts, and screws for pressure vessels, valves, flanges, fittings at elevated temperatures

Common Grades

B7Cr-Mo Alloy, 125 ksi min tensile
B7MB7 with max 99 HRB (NACE sour service)
B8 (Class 1)SS 304, 75 ksi tensile, strain hardened
B8M (Class 2)SS 316, 125 ksi min (strain hardened)
B16Cr-Mo-V, high temperature service
L7Low-alloy steel for low temp service

Key Requirements

Size Range¼” to 4″ (UNC) / M6 to M100
Thread FormUNC / UNF per ASME B1.1
Test CertificateMill Test Report (MTR) mandatory
HardnessB7: 35 HRC max; B7M: 99 HRB max
Charpy ImpactRequired for B8 Class 2 (–196°C)
ApplicationFlanges, pressure vessels, piping
ASTM

A194 — Nuts for High-Pressure / High-Temperature Service

Heavy hex nuts for use with A193 stud bolts on pressure vessels, boilers, and piping systems

Common Grades

2HCarbon steel, heavy hex, 175,000 psi proof
2HM2H with NACE hardness restriction (≤26 HRC)
8SS 304 austenitic
8MSS 316 austenitic (Mo-bearing)
8MASS 316 annealed condition
4Alloy steel, quenched & tempered

Key Requirements

StyleHeavy Hex per ASME B18.2.2
Proof LoadMust withstand proof load per grade
Hardness (2H)C24–C35 Rockwell
MarkingGrade marking on flat face mandatory
Pairing8M nuts used with B8M studs
CoatingHot dip galvanized or plain per order

Structural Bolting Standards

StandardFastener TypeGrade / TypeTensile StrengthYield StrengthApplication
ASTM A307Bolts, StudsGrade A / B60 ksi min—Low-carbon general purpose
ASTM A325Structural BoltsType 1 / 3120 ksi (≤1″)92 ksiSteel-to-steel structural connections
ASTM A490Structural BoltsType 1 / 2 / 3150–170 ksi130 ksiHigh-strength structural connections
ASTM F3125Structural BoltsA325M / A490MMetric equiv.Metric equiv.Replaces A325/A490 metric
ASTM F593SS Bolts & ScrewsGroup 1 / 2 / 365–100 ksi30–65 ksiStainless steel general purpose
ASTM F594SS NutsGroup 1 / 2 / 3Proof 65–100 ksi—Mating nuts for F593 bolts
Note: ASTM A325 and A490 are formally discontinued and replaced by ASTM F3125. However, both designations remain widely specified by engineers and project owners. HITECH Fastener supplies to both the legacy and replacement standard designations.
German Standards

DIN Standards — Detailed Reference

DIN standards are published by Deutsches Institut für Normung. Many have been superseded by EN ISO equivalents but remain actively specified. HITECH supplies to both DIN and EN ISO.

DIN No.DescriptionThread RangeISO EquivalentProduct Form
DIN 931Hex Bolt — Partially ThreadedM5 – M52ISO 4014Bolt
DIN 933Hex Bolt — Fully ThreadedM1.6 – M52ISO 4017Bolt
DIN 934Hex Nut (standard)M1.6 – M52ISO 4032Nut
DIN 976-1Metric Threaded Stud / StudboltM3 – M52ISO 4028Stud
DIN 975Threaded Rod (full length)M3 – M52ISO 4028Threaded Rod
DIN 7991Countersunk Socket Cap ScrewM3 – M20ISO 10642Screw
DIN 912Socket Head Cap ScrewM1.6 – M52ISO 4762Screw
DIN 916Socket Set Screw (cup point)M1.6 – M24ISO 4029Set Screw
DIN 6923Hex Flange NutM5 – M20ISO 4161Nut
DIN 127Spring Lock WasherM3 – M36ISO 7090Washer
DIN 125Flat Washer (Form A)M3 – M36ISO 7089Washer
DIN 2093Disc Spring (Belleville)Various—Spring Washer
DIN 935Castle / Slotted NutM4 – M52ISO 7035Nut
DIN 985Nyloc / Prevailing Torque NutM3 – M36ISO 10511Nut
DIN → EN ISO Transition: Most DIN fastener standards issued before 1990 have been withdrawn and replaced by harmonised EN ISO standards. When specifying DIN 931 today, the technically equivalent product is ISO 4014 / EN ISO 4014. HITECH Fastener accepts orders against both designations and supplies to the current applicable standard unless otherwise noted.
International Standards

ISO Standards — Comprehensive Reference

ISO 898-1 — Mechanical Property Classes (Metric Bolts & Screws)

Property ClassMaterialMin Tensile (MPa)Min Yield / Proof (MPa)Hardness (HRB/HRC)Common Use
4.6Low / medium carbon steel40024067–95 HRBLight general purpose
4.8Low / medium carbon steel42034071–95 HRBGeneral purpose
5.6Low carbon steel, quenched50030079–95 HRBStructural light load
5.8Low / medium carbon52042082–95 HRBGeneral machinery
6.8Medium carbon steel60048089–95 HRBGeneral engineering
8.8Medium carbon alloy, QT80064022–32 HRCMost widely used structural grade
9.8Medium carbon alloy, QT90072026–34 HRC≤M16, machinery
10.9Alloy steel, QT104094033–39 HRCHigh-strength structural / automotive
12.9Alloy steel, QT1220110039–44 HRCUltra-high strength, critical applications

ISO 3506 — Stainless Steel Fastener Property Classes

ClassSS GradeTensile (MPa)Yield 0.2% (MPa)Elongation %Magnetic
A2-50SS 304 / 3025002100.6dNo
A2-70SS 304 / 302 (cold worked)7004500.4dSlightly
A2-80SS 304 (heavily cold worked)8006000.3dSlightly
A4-50SS 316 / 316L5002100.6dNo
A4-70SS 316 (cold worked)7004500.4dSlightly
A4-80SS 316 (heavily cold worked)8006000.3dSlightly
F1-45SS 410 Martensitic4502500.2dYes
C1-70SS 410 (hardened & tempered)700560—Yes

Key ISO Dimensional Standards

Bolts & Screws

  • ISO 4014 — Hex bolt, partial thread
  • ISO 4016 — Hex bolt, partial thread, product grade C
  • ISO 4017 — Hex bolt, full thread
  • ISO 4762 — Socket head cap screw
  • ISO 10642 — Countersunk socket cap screw
  • ISO 4026–4029 — Socket set screws

Nuts

Washers, Thread & Testing

  • ISO 7089 — Flat washer, normal series
  • ISO 7090 — Flat washer, normal series, chamfered
  • ISO 7093 — Flat washer, large series
  • ISO 724 — Metric thread (M profile)
  • ISO 965 — Metric thread tolerances
  • ISO 6157 — Surface discontinuities
Pressure Equipment Standards

ASME Standards — Bolting for Pressure Vessels & Piping

ASME B18 Series — Dimensional Standards

StandardCoverage
ASME B18.2.1Square & Hex Bolts / Screws (UNC/UNF) — Imperial
ASME B18.2.2Square & Hex Nuts — Imperial
ASME B18.2.3.5MMetric Hex Bolts
ASME B18.2.4.6MMetric Heavy Hex Nuts
ASME B18.3Socket Cap, Set & Shoulder Screws
ASME B18.21.1Lock Washers (Inch)
ASME B18.22.1Plain Washers (Inch)
ASME B18.31.1MMetric Continuous Thread Studs

ASME SA / A — Material Standards

StandardGradeApplication
SA-193 B7Cr-Mo alloy steelHigh temp stud bolting
SA-193 B7MB7 NACE restrictedSour service (H₂S)
SA-193 B8MSS 316 CWCryogenic stud bolts
SA-194 2HCarbon steelHeavy hex nuts for B7
SA-194 8MSS 316Nuts for B8M studs
SA-320 L7Alloy steelLow temperature service
SA-307Low carbon steelFlanges, light structural

ASME PCC-1 — Guidelines for Pressure Boundary Bolted Flange Joint Assembly

ASME PCC-1 is not a dimensional or material standard — it is the industry-recognised best-practice guideline for assembling bolted flange joints. It prescribes bolt lubrication requirements, torquing sequences (cross-pattern, multi-pass), use of hydraulic bolt tensioners vs. torque wrenches, and documentation practices. Compliance is increasingly required by EPC contractors and process plant owners globally.

British & European Standards

BS / EN Standards Reference

StandardDescriptionScopeReplaces
EN ISO 4014Hex bolts, product grades A & B, partial threadM1.6–M64BS 3692 / DIN 931
EN ISO 4017Hex bolts, product grades A & B, full threadM1.6–M64BS 3692 / DIN 933
EN ISO 4032Hex nuts, style 1, product grades A & BM1.6–M64BS 3692 / DIN 934
EN ISO 4033Hex nuts, style 2 (thicker), high strengthM5–M64BS 3692
EN 14399-3HR bolts for structural preloaded applicationsM12–M36BS 4395
EN 14399-4HV bolts for structural preloaded connectionsM12–M36BS 4395
EN ISO 898-1Mechanical properties — bolts & screwsAll metricBS EN 24014
EN ISO 3506-1SS bolt mechanical propertiesAll metricBS EN ISO 3506
EN ISO 7089Plain washers, normal seriesM1.6–M64BS 4320
BS 1769Machine screws and machine screw nutsBA, UNC/UNFActive (niche)
BS 4190ISO metric black hexagon bolts, screws & nutsM5–M72Active (construction)
BS EN ISO: Standards prefixed “BS EN ISO” are British Standards that adopt both the European (EN) and International (ISO) version of a standard — the three bodies harmonise to a single text. These are the current preferred designations for UK and European procurement.
Japanese Standards

JIS Standards Reference

JIS (Japanese Industrial Standards) are specified by Japanese OEMs, automotive manufacturers, and process plant builders. HITECH Fastener supplies JIS-compliant fasteners for export to Japan and Japanese-owned plants globally.

JIS No.DescriptionSize RangeISO Equiv.
JIS B 1180Hexagon Head Bolts (coarse thread)M1.6–M64ISO 4014 / 4017
JIS B 1181Hexagon Nuts (style 1)M1.6–M64ISO 4032
JIS B 1176Hexagon Socket Head Cap ScrewsM1.6–M36ISO 4762
JIS B 1177Hexagon Socket Set ScrewsM1.6–M24ISO 4026–4029
JIS B 1256Plain WashersM1.6–M52ISO 7089
JIS B 2220Steel Pipe FlangesPN seriesASME B16.5 equiv.
JIS G 4303Stainless Steel Bars (SUS304, SUS316)—ASTM A276 equiv.
JIS B 1051Mechanical Properties — Bolts, Screws—ISO 898-1
Quick Reference

Product × Standards Matrix

Which standards apply to which product type — at a glance.

Product ASTMDINISOASMEBS/ENJIS
Hex Bolts (Carbon Steel) ✓✓✓ ✓✓✓
Hex Bolts (Stainless Steel) ✓✓✓ ✓✓✓
Stud Bolts (High Pressure) ✓✓✓ ✓✓—
Heavy Hex Nuts ✓✓✓ ✓✓✓
Socket Cap Screws —✓✓ ✓✓✓
Threaded Rods ✓✓✓ ✓✓—
Flat Washers ✓✓✓ ✓✓✓
Structural Bolts (8.8 / 10.9) ✓✓✓ ✓✓—
Flange Bolts (Pressure Vessel) ✓—— ✓✓—
Eye Bolts / U-Bolts ✓✓✓ —✓—
Cross-Reference

Cross-Standard Comparison Table

Equivalent standards across ASTM, ISO/DIN, BS/EN, and JIS for common fastener types.

ProductASTM / ASMEISO / DINBS / ENJIS
Hex Bolt (partial thread)ASTM A307 / F3125ISO 4014 / DIN 931BS EN ISO 4014JIS B 1180
Hex Bolt (full thread)ASTM A307ISO 4017 / DIN 933BS EN ISO 4017JIS B 1180
High-Str. Hex Bolt (8.8)ASTM A325 / F3125ISO 898-1 Cl 8.8EN 14399-3 Grade 8.8JIS B 1051 Cl 8.8
High-Str. Hex Bolt (10.9)ASTM A490 / F3125ISO 898-1 Cl 10.9EN 14399-3 Grade 10.9JIS B 1051 Cl 10.9
Hex Nut (standard)ASTM A563 Grade CISO 4032 / DIN 934BS EN ISO 4032JIS B 1181
Heavy Hex NutASTM A194 Grade 2HISO 4033BS EN ISO 4033—
Stud Bolt (PV)ASTM A193 B7 / SA-193ISO 4028 / DIN 976BS EN 20898—
SS BoltASTM F593 (Group 1–3)ISO 3506 A2-70 / A4-70BS EN ISO 3506-1JIS G 4303
SS NutASTM F594ISO 3506 A2-70 / A4-70BS EN ISO 3506-2JIS G 4303
Flat WasherASTM F844ISO 7089 / DIN 125BS EN ISO 7089JIS B 1256
Socket Cap ScrewASTM A574ISO 4762 / DIN 912BS EN ISO 4762JIS B 1176
Threaded RodASTM A193 / A307ISO 4028 / DIN 975BS 4190—
Identification

Bolt Head Marking Guide

Head markings identify the property class or grade, manufacturer, and standard. Correct marking is mandatory per most standards.

MarkingStandardGrade / ClassMaterialTypical Head Colour (if coated)
No markingASTM A307Grade ALow carbon steelPlain / Black oxide
3 radial linesASTM A325Type 1Medium carbon alloyYellow (zinc chromate)
6 radial linesASTM A490Type 1Alloy steel, QTGrey (phosphate)
“B7” + mfr logoASTM A193Grade B7Cr-Mo alloyPlain / Phosphate
“B8M” + mfr logoASTM A193Grade B8MSS 316Plain (stainless)
“8.8” embossedISO 898-1Class 8.8Medium carbon alloyYellow zinc
“10.9” embossedISO 898-1Class 10.9Alloy steel QTPlain / Phosphate
“12.9” embossedISO 898-1Class 12.9Alloy steel QTBlack phosphate
“A2-70” embossedISO 3506A2-70SS 304Plain (stainless)
“A4-80” embossedISO 3506A4-80SS 316 CWPlain (stainless)
Tip: All head markings must also include the manufacturer’s identification mark (logo or code). Fasteners without a manufacturer’s mark cannot be positively traced and may be rejected by quality inspectors on critical projects.
Thread Tolerances

Thread Tolerance Classes

Metric Threads (ISO 965 / ISO 724)

ClassApplicationFit QualityUse Case
6g (External)Bolts / ScrewsMediumGeneral purpose, preferred class
6H (Internal)NutsMediumGeneral purpose nut thread
4g / 6gBolts (coated)Allows for coatingHot-dip galvanized bolts
4H / 5HNuts (coated)Oversize tappedNuts for galvanized bolts
3g / 3hPrecision boltsCloseFine machinery, gauging

Unified Threads (ASME B1.1)

ClassApplicationFit QualityUse Case
1A (External)BoltsLooseEasy assembly in dirty/damaged conditions
1B (Internal)NutsLooseMating nut for Class 1A
2A (External)BoltsMediumGeneral commercial — most common
2B (Internal)NutsMediumMost common commercial nut
3A (External)Precision boltsCloseAerospace, critical assemblies
3B (Internal)Precision nutsCloseMating Class 3A bolts
Strength Reference

Property Class & Grade Cross-Reference

A side-by-side comparison of metric property classes (ISO) and inch grade markings (ASTM/SAE).

ISO ClassSAE GradeASTM GradeTensile (MPa)Yield (MPa)HardnessTypical Alloy
4.6Grade 2A307 Gr A40024067–95 HRBLow carbon steel
5.8——52042082–95 HRBLow/med carbon
8.8Grade 5A325 Type 180064022–32 HRCMed carbon alloy, QT
10.9Grade 8A490 Type 1104094033–39 HRCAlloy steel, QT
12.9Grade 8 (≈)—1220110039–44 HRCAlloy steel, QT (ultra)
A2-50—F593 Gr 1500210—SS 304 annealed
A2-70—F593 Gr 2700450—SS 304 cold worked
A4-70—F593 Gr 2700450—SS 316 cold worked
A4-80—F593 Gr 3800600—SS 316 heavily CW
Quality Assurance

Testing Standards & Methods

01

ASTM A370 — Mechanical Testing

Standard test methods for mechanical testing of steel products. Covers tensile, yield, elongation, hardness (Rockwell, Brinell, Vickers), and bend tests for fastener certifications.

02

ASTM E18 — Rockwell Hardness

Defines the procedure for Rockwell hardness testing of metallic materials. Used to verify compliance with hardness limits in A193, A194, A325, A490, and ISO 898-1 fastener standards.

03

ASTM E384 — Vickers / Knoop Hardness

Microindentation hardness testing for small fasteners, thin sections, heat-affected zones, and case-hardened layers. Required for NACE MR0175 sour service hardness verification.

04

ASTM A262 — Intergranular Corrosion

Practices A–E test sensitized stainless steel for susceptibility to intergranular corrosion. Practice E (Copper-Copper Sulfate) commonly specified for 304/316 weld assemblies and flanges.

05

ASTM B117 — Salt Spray Test

Standard test method for neutral salt spray (fog) testing of coated fasteners. 48, 96, 240, or 500 hour exposure periods per coating type. Passes: no base metal corrosion.

06

ISO 6157 — Surface Discontinuities

Defines acceptable surface defects (seams, laps, cracks, burrs) on fasteners. Part 1 for bolts/screws; Part 3 for nuts. Inspection per acceptance criteria using optical magnification.

07

ASTM E1417 — Liquid Penetrant Testing

Procedure for liquid penetrant examination of parts. Detects surface-open defects (cracks, laps, cold shuts) on critical fasteners. Required for aerospace and pressure equipment applications.

08

ASTM E317 / EN 10307 — Ultrasonic Testing

UT inspection detects internal flaws — voids, inclusions, laminations — in large-diameter stud bolts and critical pressure equipment fasteners. Phased-array UT available.

09

EN 10204 — Test Certificate Types

Type 2.1: Declaration of compliance. Type 2.2: Test report. Type 3.1: Inspection certificate (mill test). Type 3.2: Inspection certificate (independent third party). 3.1 is standard export documentation.

FAQ

Frequently Asked Questions

What is the difference between ASTM A193 B7 and B7M?
Both are chromium-molybdenum alloy steel stud bolts, but B7M has a maximum hardness restriction of 99 HRB (equivalent to ~23 HRC). This restriction is required for sour service (hydrogen sulphide environments) per NACE MR0175 / ISO 15156. B7 has no such hardness limit and is used in standard high-temperature pressure applications. Both grades have identical composition requirements.
What does ISO property class “8.8” mean?
The two numbers indicate: the first digit × 100 = minimum tensile strength in MPa (8 × 100 = 800 MPa); the second digit × 10% of tensile = minimum yield strength (0.8 × 800 = 640 MPa). So an 8.8 bolt has minimum tensile of 800 MPa and minimum yield of 640 MPa. For 10.9: tensile = 1040 MPa, yield = 940 MPa.
Can I substitute DIN 931 with ISO 4014?
For most applications, yes — ISO 4014 is the direct metric equivalent and successor to DIN 931 for partial-thread hex bolts. Dimensions are almost identical, with minor differences in tolerance and surface quality grades. ISO 4014 covers product grades A and B; if product grade C is required, use ISO 4016. Always verify with your engineering team before substituting standards on critical applications.
What is the difference between A2-70 and A4-70 stainless steel bolts?
Both are austenitic stainless steel grades per ISO 3506 with the same mechanical properties (700 MPa tensile, 450 MPa yield). The key difference is the base alloy: A2 = 300 series austenitic (typically SS 304), A4 = 300 series with molybdenum (typically SS 316). A4-70 has significantly better resistance to chlorides and pitting — it is the preferred grade for marine, offshore, and chemical environments.
What test certificate do I need for export to Europe?
For standard commercial export to Europe, EN 10204 Type 2.2 (test report) or Type 3.1 (mill inspection certificate) is typically acceptable. For pressure equipment under PED (Pressure Equipment Directive), Type 3.1 is generally required minimum. For nuclear, subsea, or high-criticality applications, Type 3.2 (independent third-party inspection) is specified. HITECH Fastener can provide 2.2, 3.1, and arrange 3.2 via TÜV or Bureau Veritas.
What is NACE MR0175 / ISO 15156 and why does it matter?
NACE MR0175 (now dual-published as ISO 15156) is the internationally recognised standard for selecting materials suitable for use in sour (hydrogen sulphide-containing) environments in oil and gas production. For fasteners, it restricts maximum hardness levels to prevent sulphide stress cracking (SSC). Common requirements: B7M bolts (≤99 HRB), 2HM nuts (≤26 HRC), SS 316 at A4-70 maximum. Non-compliance in H₂S service can result in brittle fracture and catastrophic failure.

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