Carriage Bolts
Carriage bolts have a smooth domed head and a square neck. The neck locks into wood or a square hole so the nut can be tightened from one side.
Carriage bolt basics
| Head | Round dome, no drive |
|---|---|
| Neck | Square, locks against rotation |
| Length | Under the head to the end, including the neck |
| Grades | Commonly Grade 2 or 18-8; Grade 5 available |
| Metric | DIN 603 / ISO 8677 |
These tables carry the same figures as the printed sheet below.
The printed sheet
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Text version of this sheet
ASME B18.5 · DIN 603 / ISO 8677 · carriage bolts
What it is
FIELD IDENTIFICATION
Carriage bolts have a smooth domed head and a square neck. The neck locks into wood or a square
hole so the nut can be tightened from one side.
Smooth domed head, square neck locks in the
hole
Carriage bolt basics
Head
Round dome, no drive
Neck
Square, locks against rotation
Length
Under the head to the end, including the neck
Grades
Commonly Grade 2 or 18-8; Grade 5 available
Metric
DIN 603 / ISO 8677
Key points
A grade mark, if any, is on the dome.
Governing standards: ASME B18.5-2012 (R2023); ISO 8677. 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-7ADC98 · thefastenerapp.com/fastener-guide/technical-reference/carriage-bolts · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.
