JIS Fastener Markings - Japanese Standards
Japanese bolts follow JIS standards that are largely aligned with ISO today, but older parts and some structural systems use their own markings and head sizes, which matters on Japanese vehicles and equipment.
Common JIS standards and marks
| Standard / mark | Meaning |
|---|---|
| JIS B 1051 | Mechanical properties of bolts (aligned with ISO 898-1): 8.8, 10.9, 12.9 |
| JIS B 1180 / B 1181 | Hexagon bolts / hexagon nuts |
| JIS B 1186, F10T | High-strength friction-grip structural bolt set, class F10T |
| S10T (JSS II 09) | Japanese tension-control structural bolt |
| 4T / 7T (older) | Older JIS strength marks, roughly 400 / 700 MPa class |
Head size differences (across flats, mm)
| Thread | ISO | Older JIS series |
|---|---|---|
| M8 | 13 | 12 |
| M10 | 16 | 14 or 17 |
| M12 | 18 | 17 or 19 |
Older Japanese vehicles and equipment often use the smaller JIS head sizes. Check with the right wrench.
These tables carry the same figures as the printed sheet below.
The printed sheet
See an error on this sheet?
Tell us what is wrong.
Text version of this sheet
JIS · Japanese Industrial Standards for bolts and nuts
What it is
FIELD IDENTIFICATION
MFG
MFG
F10T
8.8
STRUCTURAL
JIS B 1051
Japanese bolts follow JIS standards that are largely aligned with ISO today, but older parts and some
structural systems use their own markings and head sizes, which matters on Japanese vehicles and
equipment.
JIS structural and property-class marks
Common JIS standards and marks
Standard / mark
Meaning
JIS B 1051
Mechanical properties of bolts (aligned with ISO 898-1): 8.8, 10.9, 12.9
JIS B 1180 / B 1181
Hexagon bolts / hexagon nuts
JIS B 1186, F10T
High-strength friction-grip structural bolt set, class F10T
S10T (JSS II 09)
Japanese tension-control structural bolt
4T / 7T (older)
Older JIS strength marks, roughly 400 / 700 MPa class
Head size differences (across flats, mm)
Thread
ISO
Older JIS series
M8
13
12
M10
16
14 or 17
M12
18
17 or 19
Older Japanese vehicles and equipment often use the smaller JIS head sizes. Check with the right wrench.
Key points
Japanese vehicles commonly use M10 x 1.25 and M12 x 1.25 fine threads; confirm pitch with a gauge.
Governing standards: JIS B 1051; JIS B 1180:2014; JIS B 1181; JIS B 1186. 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-2E00CE · thefastenerapp.com/fastener-guide/technical-reference/jis-fastener-markings · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.
