1/2" Grade 8 Torque Specification

Torque Values by Surface Condition

Stress area: 0.1419 in² · Proof load: 17,028 lbs · Clamp load (75%): 12,771 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	106.4	144.3	1276.8	1471.5
Oiled	0.15	79.8	108.2	957.6	1103.3
Zinc Plated	0.18	95.8	129.9	1149.6	1324.6
Waxed	0.1	53.2	72.1	638.4	735.2
MoS₂	0.12	63.9	86.6	766.8	883.1
Galvanized	0.25	133.0	180.3	1596.0	1838.6

Stress area: 0.1599 in² · Proof load: 19,188 lbs · Clamp load (75%): 14,391 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	119.9	162.6	1438.8	1658.1
Oiled	0.15	89.9	121.9	1078.8	1243.0
Zinc Plated	0.18	107.9	146.3	1294.8	1491.9
Waxed	0.1	60.0	81.3	720.0	829.0
MoS₂	0.12	72.0	97.6	864.0	995.2
Galvanized	0.25	149.9	203.2	1798.8	2072.1

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 120,000 psi × 0.1419 in² = 12,771 lbs

Step 2 — Torque (dry): T = 0.20 × 0.5 in × 12,771 lbs ÷ 12 = 106.4 ft·lbs

Proof stress per SAE J429 Table 3. Stress area per ASME B1.1. K-factor per VDI 2230.

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

• 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.

Size1/2"

Grade8

Diameter0.5" (12.70 mm)

TPI (UNC)13

Tensile150,000 psi

Yield130,000 psi

Proof120,000 psi