How to Read This Guide - Grades, Classes and Systems
Fastener strength is described in different ways in different systems. Mixing them up is the most common and most dangerous mistake. This page explains how to tell them apart.
The four languages
| System | Looks like | Standard | Example |
|---|---|---|---|
| Inch grade | Radial lines on the head | SAE J429 | 3 lines = Grade 5 |
| Metric property class | Two numbers | ISO 898-1 | 8.8, 10.9, 12.9 |
| Structural system | Grade name + matched nut and washer | ASTM F3125, EN 14399, AS/NZS 1252, JIS B 1186 | A325, HV 10.9, 8.8/S, F10T |
| Stainless | Alloy or class mark | ASTM F593, ISO 3506 | F593C, A2-70, A4-80 |
Product standard vs material standard
| Question | Answered by | Example |
|---|---|---|
| What shape and size? | Product standard | ASME B18.2.1, ISO 4017, ISO 4762 |
| How strong? | Material / property standard | SAE J429, ISO 898-1, ASTM A574 |
| What coating? | Coating standard | ASTM F1941, ASTM F2329, ASTM F3393 |
These tables carry the same figures as the printed sheet below.
The printed sheet
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Text version of this sheet
Start here · inch grades, metric property classes and structural systems
What it is
FIELD IDENTIFICATION
Fastener strength is described in different ways in different systems. Mixing them up is the most
common and most dangerous mistake. This page explains how to tell them apart.
MFG
MFG
MFG
8.8
A325
INCH GRADE
METRIC CLASS
STRUCTURAL
Three different strength languages
The four languages
System
Looks like
Standard
Example
Inch grade
Radial lines on the head
SAE J429
3 lines = Grade 5
Metric property class
Two numbers
ISO 898-1
8.8, 10.9, 12.9
Structural system
Grade name + matched nut and washer
ASTM F3125, EN 14399, AS/NZS 1252, JIS B 1186
A325, HV 10.9, 8.8/S, F10T
Stainless
Alloy or class mark
ASTM F593, ISO 3506
F593C, A2-70, A4-80
Product standard vs material standard
Question
Answered by
Example
What shape and size?
Product standard
ASME B18.2.1, ISO 4017, ISO 4762
How strong?
Material / property standard
SAE J429, ISO 898-1, ASTM A574
What coating?
Coating standard
ASTM F1941, ASTM F2329, ASTM F3393
Key points
A strength cousin is not a substitute: Grade 5 is not 8.8, Grade 8 is not 10.9, and none of them is a structural bolt.
A part that threads together is not automatically a correct engineering match.
Every sheet cites its governing standards. The drawing and the current standard always win over this guide.
Governing standards: SAE J429 (2014); ISO 898-1:2013; ASTM F3125/F3125M-26; EN 14399; AS/NZS 1252; ISO 3506-1/-2:2020. Editions shown are the latest confirmed as of
September 2026. The drawing and the governing standard always take precedence over this sheet.
torquing any fastener. Verify the current governing standard, project documents, OEM requirements, size, thread, coating and lot certification. To the fullest extent permitted by law, The Fastener App disclaims liability
arising from reliance on this reference.
Fastener Guide reference FG-0E0D5D · thefastenerapp.com/fastener-guide/technical-reference/how-to-read-this-guide · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.
