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Have you ever wondered what the markings on the head of a bolt mean? Maybe it’s just a few lines or a series of letters and numbers.
The markings on bolt heads serve two different purposes:
1. The markings can indicate who manufactured the bolt.
- This will vary from manufacturer to manufacturer, but is usually one, two or three characters.
2. The markings can identify the standard to which the bolt was made.
For instance:
- If a bolt head contains three radial lines, then it’s a Grade 5 bolt. & if it contains five radial lines, then the bolt is Grade 8.
- If the bolt is manufactured to a particular grade based on standards set by the American Society for Testing and Materials (ASTM), then the marking will show a combination of letters and numbers.
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