1-3/8" Grade 2 Bolt Torque: 655.1 ft·lbs / 888.2 N·m

Torque Values by Surface Condition

UNC — Coarse Thread — 6 TPI

Stress area: 1.155 in² · Proof load: 38,115 lbs · Clamp load (75%): 28,586 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	655.1	888.2	7861.2	9057.1
Oiled	0.15	491.3	666.1	5895.9	6792.8
Zinc Plated	0.18	589.6	799.4	7075.1	8151.4
Waxed	0.1	327.5	444.0	3930.6	4528.6
MoS₂	0.12	393.1	533.0	4716.7	5434.3
Galvanized	0.25	818.9	1110.3	9826.5	11321.4

UNF — Fine Thread — 12 TPI

Stress area: 1.315 in² · Proof load: 43,395 lbs · Clamp load (75%): 32,546 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	745.8	1011.2	8950.2	10311.8
Oiled	0.15	559.4	758.4	6712.7	7733.8
Zinc Plated	0.18	671.3	910.2	8055.2	9280.6
Waxed	0.1	372.9	505.6	4475.1	5155.9
MoS₂	0.12	447.5	606.7	5370.1	6187.1
Galvanized	0.25	932.3	1264.0	11187.8	12889.7

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 327.5 ft·lbs (waxed) to 818.9 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 × 1.155 in² = 28,586 lbs

Step 2 — Torque (dry): T = 0.20 × 1.375 in × 28,586 lbs ÷ 12 = 655.1 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

Size1-3/8"

Grade2

Diameter1.375" (34.92 mm)

TPI (UNC)6

Tensile60,000 psi

Yield36,000 psi

Proof33,000 psi

1-3/8" Grade 2 Torque Spec