TABLE OF CONTENTS Grade Marks and Material Properties for Bolts and Screws. Bolts, screws, and other fasteners are marked on the head with a symbol that identifies the grade of the fastener. The grade specification establishes the minimum mechanical properties that the fastener must meet. Additionally, industrial fasteners must be stamped with a registered head mark that identifies the manufacturer. The grade identification table identifies the grade markings and gives mechanical properties for some commonly used ASTM and SAE steel fasteners. Metric fasteners are identified by property grade marks, which are specified in ISO and SAE standards. These marks are discussed with metric fasteners.
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| Identifier | Grade | Size (in.) | Min. Strength (10 3 psi) | Material & Treatment | ||
| Proof | Tensile | Yield | ||||
| A | SAE Grade 1 | 1/4 to 1 1/2 | 33 | 60 | 36 | 1 |
| ASTM A307 | 1/4 to 1 1/2 | 33 | 60 | 36 | 3 | |
| SAE Grade 2 | 1/4 to 3/4 | 55 | 74 | 57 | 1 | |
| 7/8 to 1 1/2 | 33 | 60 | 36 | |||
| SAE Grade 4 | 1/4 to 1 1/2 | 65 | 115 | 100 | 2, a | |
| B | SAE Grade 5 | 1/4 to 1 | 85 | 120 | 92 | 2,b |
| ASTM A449 | 1 1/8 to 1 1/2 | 74 | 105 | 81 | ||
| ASTM A449 | 1 3/4 to 3 | 55 | 90 | 58 | ||
| C | SAE Grade 5.2 | 1/4 to 1 | 85 | 120 | 92 | 4, b |
| D | ASTM A325, Type 1 | 1/2 to 1 | 85 | 120 | 92 | 2,b |
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