How to Read a Fastener Specification
A complete fastener line is a sentence, not a diameter. Missing any part of it is how the wrong part ships.
Anatomy of a callout: 1/2-13 x 2 Hex Cap Screw, SAE J429 Grade 5, Zinc
| Part | Example | Why it matters |
|---|---|---|
| Diameter | 1/2 | Nominal size |
| Thread | 13 (UNC) | Coarse vs fine |
| Length | 2 in | Measured per head style |
| Product | Hex cap screw | Sets dimensions and tolerances |
| Grade / spec | SAE J429 Grade 5 | Sets strength |
| Finish | Zinc (ASTM F1941) | Sets corrosion and torque |
| Extras | Thread length, certs, packaging | Anything else the job needs |
Governing standards: ASME B18.2.1-2012 (R2021); SAE J429 (2014); ASTM F1941/F1941M-16(2025). Editions shown are the latest confirmed as of September 2026. The drawing and the governing standard always take precedence over this sheet.
These tables carry the same figures as the printed sheet below.
The printed sheet
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Tell us what is wrong.
Text version of this sheet
Reading a fastener callout
What it is
FIELD IDENTIFICATION
A complete fastener line is a sentence, not a diameter. Missing any part of it is how the wrong part
ships.
L
D
1/2-13 x 2 HEX CAP SCREW GR 5 ZINC
Diameter-thread x length, product, grade, finish
Anatomy of a callout: 1/2-13 x 2 Hex Cap Screw, SAE J429 Grade 5, Zinc
Part
Example
Why it matters
Diameter
1/2
Nominal size
Thread
13 (UNC)
Coarse vs fine
Length
2 in
Measured per head style
Product
Hex cap screw
Sets dimensions and tolerances
Grade / spec
SAE J429 Grade 5
Sets strength
Finish
Zinc (ASTM F1941)
Sets corrosion and torque
Extras
Thread length, certs, packaging
Anything else the job needs
Governing standards: ASME B18.2.1-2012 (R2021); SAE J429 (2014); ASTM F1941/F1941M-16(2025). 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-4639A3 · thefastenerapp.com/fastener-guide/technical-reference/how-to-read-a-fastener-specification · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.
