7/8" Grade 8 Torque Specification

Torque Values by Surface Condition

Stress area: 0.462 in² · Proof load: 55,440 lbs · Clamp load (75%): 41,580 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	606.4	822.2	7276.8	8384.1
Oiled	0.15	454.8	616.6	5457.6	6287.6
Zinc Plated	0.18	545.7	739.9	6548.4	7544.9
Waxed	0.1	303.2	411.1	3638.4	4192.1
MoS₂	0.12	363.8	493.2	4365.6	5029.3
Galvanized	0.25	758.0	1027.7	9096.0	10479.7

Stress area: 0.509 in² · Proof load: 61,080 lbs · Clamp load (75%): 45,810 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	668.1	905.8	8017.2	9236.6
Oiled	0.15	501.0	679.3	6012.0	6927.0
Zinc Plated	0.18	601.3	815.3	7215.6	8313.8
Waxed	0.1	334.0	452.8	4008.0	4617.3
MoS₂	0.12	400.8	543.4	4809.6	5541.2
Galvanized	0.25	835.1	1132.2	10021.2	11545.3

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 120,000 psi × 0.462 in² = 41,580 lbs

Step 2 — Torque (dry): T = 0.20 × 0.875 in × 41,580 lbs ÷ 12 = 606.4 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.

Size7/8"

Grade8

Diameter0.875" (22.22 mm)

TPI (UNC)9

Tensile150,000 psi

Yield130,000 psi

Proof120,000 psi