7/16" Grade 8 Bolt Torque: 69.8 ft·lbs / 94.6 N·m

Torque Values by Surface Condition

UNC — Coarse Thread — 14 TPI

Stress area: 0.1063 in² · Proof load: 12,756 lbs · Clamp load (75%): 9,567 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	69.8	94.6	837.1	964.5
Oiled	0.15	52.3	70.9	627.8	723.3
Zinc Plated	0.18	62.8	85.1	753.4	868.0
Waxed	0.1	34.9	47.3	418.6	482.2
MoS₂	0.12	41.9	56.8	502.3	578.7
Galvanized	0.25	87.2	118.2	1046.4	1205.6

UNF — Fine Thread — 20 TPI

Stress area: 0.1187 in² · Proof load: 14,244 lbs · Clamp load (75%): 10,683 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	77.9	105.6	934.8	1077.0
Oiled	0.15	58.4	79.2	701.1	807.7
Zinc Plated	0.18	70.1	95.0	841.3	969.3
Waxed	0.1	38.9	52.7	467.4	538.5
MoS₂	0.12	46.7	63.3	560.9	646.2
Galvanized	0.25	97.4	132.1	1168.5	1346.2

Torque by surface condition

UNC thread, ft·lbs. Values from the table above.

Same bolt, same target clamp load: thread friction alone moves the required torque from 34.9 ft·lbs (waxed) to 87.2 ft·lbs (hot-dip galvanized), 2.5× as much. Match the row to the fastener's actual finish and lubrication.

How This Value Is Calculated

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 120,000 psi × 0.1063 in² = 9,567 lbs

Step 2 — Torque (dry): T = 0.20 × 0.4375 in × 9,567 lbs ÷ 12 = 69.8 ft·lbs

Proof stress per SAE J429 Table 3. Stress area per ASME B1.1. Typical K-factor, consistent with VDI 2230 friction values.

When to Use Grade 8

High-strength applications, heavy equipment, critical joints, suspension components, trailer hitches. Equivalent to ISO 10.9.

Important Notes

• Torque values are for standard hex bolts with unified threads per ASME B1.1. Socket head cap screws may have different requirements.
• Lubrication reduces required torque significantly — using dry torque values on lubricated bolts risks exceeding yield strength.
• For critical or safety-related applications, always consult the manufacturer's specifications or applicable design standard.
• Re-used bolts may have altered friction characteristics. Inspect threads before reuse.

Specifications

Size7/16"

Grade8

Diameter0.4375" (11.11 mm)

TPI (UNC)14

Tensile150,000 psi

Yield130,000 psi

Proof120,000 psi

7/16" Grade 8 Torque Spec