Free SAE Grade 8 Bolt Torque Chart
Download a print-ready SAE/imperial torque specification chart for Grade 8 hardware. Covers 1/4 inch through 1-1/2 inch thread sizes with N•m and lb-ft values. Built for heavy-duty repair shops by ShopView.
Imperial Torque Specs You Can Actually Use
Every shop needs a torque reference that doesn't require flipping through a 300-page manual. This chart covers SAE/imperial thread sizes from 1/4" all the way up to 1-1/2" for Grade 8 hardware. Download, print, and put it where your techs can see it.
- Grade 8 SAE hardware - 1/4" through 1-1/2"
- Both N•m and lb-ft/lb-in values included
- Based on Caterpillar SENR3130 specifications
- Print-ready 300 DPI high-resolution PNG
- 4" x 7" magnet / sticker size
When to Use This SAE/Imperial Torque Chart
SAE Grade 8 is the highest common bolt grade used in heavy-duty truck and equipment applications. With a minimum tensile strength of 150,000 PSI and a proof load of 120,000 PSI, Grade 8 bolts are used wherever maximum clamping force and fatigue resistance are required — frame bolts, suspension brackets, wheel studs, driveline components, and structural connections on Class 5 through Class 8 trucks.
You can identify a Grade 8 bolt by the six radial lines stamped on the head (Grade 5 has three). This is important because you should never substitute a Grade 5 bolt where a Grade 8 is specified — the lower strength can lead to fastener failure under load.
These torque values apply to clean, dry, steel-into-steel applications. If the bolt threads into aluminum, use half the torque value shown. If the fastener is lubricated or has a prevailing torque locknut, the values will differ — always check the OEM service manual for those cases.
Imperial Torque Quick Reference
Grade 8 SAE hardware torque specifications with tolerances. Values are for clean, dry, steel-into-steel applications. Based on Caterpillar SENR3130. Always refer to the OEM service manual when available.
| Thread Size | Torque (N•m) | Torque (Imperial) |
|---|---|---|
| 1/4" | 12 ± 3 N•m | 105 ± 27 lb in |
| 5/16" | 25 ± 6 N•m | 220 ± 53 lb in |
| 3/8" | 47 ± 9 N•m | 35 ± 7 lb ft |
| 7/16" | 70 ± 15 N•m | 50 ± 11 lb ft |
| 1/2" | 105 ± 20 N•m | 75 ± 15 lb ft |
| 9/16" | 160 ± 30 N•m | 120 ± 22 lb ft |
| 5/8" | 215 ± 40 N•m | 160 ± 30 lb ft |
| 3/4" | 370 ± 50 N•m | 275 ± 37 lb ft |
| 7/8" | 620 ± 80 N•m | 460 ± 60 lb ft |
| 1" | 900 ± 100 N•m | 660 ± 75 lb ft |
| 1-1/8" | 1300 ± 150 N•m | 960 ± 110 lb ft |
| 1-1/4" | 1800 ± 200 N•m | 1320 ± 150 lb ft |
| 1-3/8" | 2400 ± 300 N•m | 1780 ± 220 lb ft |
| 1-1/2" | 3100 ± 350 N•m | 2280 ± 260 lb ft |
For use on Grade 8 hardware. Specifications taken from Caterpillar SENR3130. Use only when service manual specifications are not available. If threads are into aluminum, use half torque.
Frequently Asked Questions
What is the torque spec for a 1/2 inch Grade 8 bolt?
A 1/2 inch Grade 8 bolt should be torqued to 105 ± 20 N•m (75 ± 15 lb-ft) when threading into steel with clean, dry threads. If the bolt threads into aluminum, use half torque: approximately 52 N•m (38 lb-ft).
What is the difference between Grade 5 and Grade 8 bolts?
Grade 5 bolts have a minimum tensile strength of 120,000 PSI, while Grade 8 bolts are rated at 150,000 PSI — about 25% stronger. Grade 5 bolts are marked with three radial lines on the head; Grade 8 bolts have six radial lines. Grade 8 is used in critical applications where higher clamping force and fatigue resistance are required, such as suspension components, frame bolts, and driveline connections.
How do I identify a Grade 8 bolt?
Grade 8 bolts are identified by six evenly spaced radial lines stamped on the bolt head. The lines radiate outward from the center like spokes on a wheel. An unmarked bolt head is typically a Grade 2 (low-carbon steel). Three radial lines indicate Grade 5. Six radial lines indicate Grade 8. Always verify the grade before selecting torque values.
Can I use Grade 5 bolts where Grade 8 is specified?
No. You should never downgrade fastener grade. If a Grade 8 bolt is specified, it's because the application requires the higher tensile strength and fatigue resistance. Substituting a Grade 5 bolt can result in fastener failure under load, which can be dangerous — especially in suspension, steering, and structural applications on heavy-duty trucks.
What does it mean to use half torque for aluminum?
When a steel bolt threads into an aluminum component (like a cylinder head, intake manifold, or aluminum housing), you should torque it to half the value shown in the chart. Aluminum threads are softer than steel and will strip at lower torque values. The "half torque" rule is a widely accepted industry guideline from Caterpillar and other OEMs for general-purpose fasteners in aluminum.
Are these torque specs the same as what Caterpillar publishes?
Yes. The torque values in this chart are taken directly from Caterpillar specification document SENR3130, which provides standard torque values for SAE fasteners. These values are intended as general guidelines when the specific service manual for your machine or truck does not provide a torque specification for a particular bolt.
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