Master Fastener Head Markings
Printable shop wall chart: Master Fastener Head Markings. Free letter-size PDF to print and post at the counter; 25 x 36 inch poster version available.
| Marking | What it is | Standard | Note |
|---|---|---|---|
| No mark (maker ID only) | Grade 2, or unknown | SAE J429 | Unmarked is not proven Grade 2 |
| 3 radial lines, 120 deg | Grade 5 (also A449) | SAE J429 / ASTM A449 | Check maker and certs |
| 6 radial lines, 60 deg | Grade 8 | SAE J429 | |
| 8.8 | Property class 8.8 | ISO 898-1 | Nominal 800 MPa |
| 10.9 | Property class 10.9 | ISO 898-1 | Nominal 1000 MPa |
| 12.9 | Property class 12.9 | ISO 898-1 | Usually socket heads |
| A325 (heavy hex) | Structural bolt | ASTM F3125 | Underlined = Type 3 |
| A490 (heavy hex) | Structural bolt | ASTM F3125 | No plating allowed |
| 307A / 307B | A307 Grade A / B, when marked | ASTM A307 | Often maker ID only |
| BC / BD | A354 Grade BC / BD | ASTM A354 | |
| B7 (on stud end) | A193 B7 alloy stud | ASTM A193 | Pair with A194 2H |
| 18-8 / 304 / 316 | Stainless alloy family | (alloy name) | Not a strength grade |
| A2-70 / A4-70 / A4-80 | Stainless group + class | ISO 3506 | A2 = 304 type, A4 = 316 type |
A grade mark with no maker mark is incomplete and suspect. A blank head is not proven Grade 2. Markings identify material grade, not the product standard.
These tables carry the same figures as the printed sheet below.
The printed sheet
25 x 36 inch poster version
For the full-size shop poster, tell us where to send it.
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Text version of this sheet
GRADE 2
GRADE 5
GRADE 8
8.8
10.9
A325
A490
316
CLASS 8.8
CLASS 10.9
A325
A490
316 SS
The marks you will see on bolt heads, grouped by standard family · lines and numbers are the grade; letters or a logo are the maker
Marking
What it is
Standard
Note
No mark (maker ID only)
Grade 2, or unknown
SAE J429
Unmarked is not proven Grade 2
3 radial lines, 120 deg
Grade 5 (also A449)
SAE J429 / ASTM A449
Check maker and certs
6 radial lines, 60 deg
Grade 8
SAE J429
8.8
Property class 8.8
ISO 898-1
Nominal 800 MPa
10.9
Property class 10.9
ISO 898-1
Nominal 1000 MPa
12.9
Property class 12.9
ISO 898-1
Usually socket heads
A325 (heavy hex)
Structural bolt
ASTM F3125
Underlined = Type 3
A490 (heavy hex)
Structural bolt
ASTM F3125
No plating allowed
307A / 307B
A307 Grade A / B, when marked
ASTM A307
Often maker ID only
BC / BD
A354 Grade BC / BD
ASTM A354
B7 (on stud end)
A193 B7 alloy stud
ASTM A193
Pair with A194 2H
18-8 / 304 / 316
Stainless alloy family
(alloy name)
Not a strength grade
A2-70 / A4-70 / A4-80
Stainless group + class
ISO 3506
A2 = 304 type, A4 = 316 type
A grade mark with no maker mark is incomplete and suspect. A blank head is not proven Grade 2. Markings identify material grade, not the product standard.
The Fastener App | TheFastenerApp.com
Fastener Guide reference FG-0FEF38 · thefastenerapp.com/fastener-guide/wall-charts/master-fastener-head-markings · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.
