Bolt Grades
Bryan Lott published on
2 min,
362 words
Bolt Grades
Bolts and Hitch Pins come in both unrated and rated. For the 4x4 application we'll be attempting to deal with rated gear only. Most hitch pins are not rated, however rated pins can be found, normally called Tractor Hitch Pins or Farm Hitch Pins. In a pinch, a properly rated bolt can be used as a hitch pin.
Below you'll find common grades of bolts/pins, identifying characteristics, and strength. In use as a hitch pin the important rating to look for is the Double Shear strength.
Common Grades
Grade 5 (8.8) 1/4" - 1"
- Identification
- 3 hash marks 120 degrees apart
- Grey/Silver in color
- Breaks suddenly
- Strength
- Proof Load: 85,000psi
- Tensile: 120,000psi
- Yield: 92,000psi
- Shear: 72,000psi (~60% of Tensile)
Max Force (lbs)
| Diameter | Single Shear | Double Shear |
|---|---|---|
| 1/4 | 3,534 | 7,069 |
| 5/16 | 5,522 | 11,045 |
| 3/8 | 7,952 | 15,904 |
| 1/2 | 14,137 | 28,274 |
| 5/8 | 22,089 | 44,179 |
| 3/4 | 31,809 | 63,617 |
| 7/8 | 43,273 | 86,546 |
| 1 | 56,549 | 113,097 |
| 1 1/4 | 77,313 | 154,625 |
| 1 1/2 | 111,330 | 222,660 |
Grade 8 (10.9)
- Identification
- 6 hash marks, one for each side of the bolt
- Bronze/Gold in color
- Yields before breaking
- Strength
- Proof Load: 120,000psi
- Tensile: 150,000psi
- Yield: 130,000psi
- Shear: 90,000psi (~60% of Tensile)
Max Force (lbs)
| Diameter | Single Shear | Double Shear |
|---|---|---|
| 1/4 | 4,418 | 8,836 |
| 5/16 | 6,903 | 13,806 |
| 3/8 | 9,940 | 19,880 |
| 1/2 | 17,671 | 35,343 |
| 5/8 | 27,612 | 55,223 |
| 3/4 | 39,761 | 79,522 |
| 7/8 | 54,095 | 108,190 |
| 1 | 70,686 | 141,372 |
| 1 1/4 | 110,447 | 220,893 |
| 1 1/2 | 159,043 | 318,086 |
Grade 9 (~12.9)
- Identification
- 9 hash marks
- Strength
- Proof Load: 145,000psi
- Tensile: 180,000psi
- Yield: 155,000psi
- Shear: 108,000psi (~60% of Tensile)
Definitions:
- Tensile Strength: The resistance of a material to breaking under tension
- Yield Strength: The stress at which a specific amount of deformation is produced
- Proof Load: An axial tensile load which the product must stand without evidence of any permanent set.
- Single Shear:
- Double Shear:
Sources:
- Bolt Grade Markings & Strength Chart
- The Tractor Hitch Pin A Critical Component in Keeping Control of Implements - Purdue Extension PPP-94 (special thanks to Chad A. for the recommendation)