7/8" Grade 2 Bolt Torque: 166.7 ft·lbs / 226.0 N·m

Torque Values by Surface Condition

UNC — Coarse Thread — 9 TPI

Stress area: 0.462 in² · Proof load: 15,246 lbs · Clamp load (75%): 11,434 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	166.7	226.0	2001.0	2305.4
Oiled	0.15	125.1	169.6	1500.8	1729.1
Zinc Plated	0.18	150.1	203.5	1800.9	2074.9
Waxed	0.1	83.4	113.1	1000.5	1152.7
MoS₂	0.12	100.0	135.6	1200.6	1383.3
Galvanized	0.25	208.4	282.6	2501.3	2881.8

UNF — Fine Thread — 14 TPI

Stress area: 0.509 in² · Proof load: 16,797 lbs · Clamp load (75%): 12,598 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	183.7	249.1	2204.6	2540.0
Oiled	0.15	137.8	186.8	1653.5	1905.0
Zinc Plated	0.18	165.3	224.1	1984.1	2286.0
Waxed	0.1	91.9	124.6	1102.3	1270.0
MoS₂	0.12	110.2	149.4	1322.8	1524.0
Galvanized	0.25	229.7	311.4	2755.8	3175.0

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 83.4 ft·lbs (waxed) to 208.4 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 × 33,000 psi × 0.462 in² = 11,434 lbs

Step 2 — Torque (dry): T = 0.20 × 0.875 in × 11,434 lbs ÷ 12 = 166.8 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 2

Large general-purpose bolts, same grade but reduced strength at larger diameters

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

Size7/8"

Grade2

Diameter0.875" (22.22 mm)

TPI (UNC)9

Tensile60,000 psi

Yield36,000 psi

Proof33,000 psi

7/8" Grade 2 Torque Spec