1-3/8" Grade 5 Bolt Torque: 1469.0 ft·lbs

Torque Values by Surface Condition

UNC — Coarse Thread — 6 TPI

Stress area: 1.155 in² · Proof load: 85,470 lbs · Clamp load (75%): 64,102 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	1469.0	1991.7	17628.2	20309.9
Oiled	0.15	1101.8	1493.8	13221.1	15232.4
Zinc Plated	0.18	1322.1	1792.5	15865.4	18278.9
Waxed	0.1	734.5	995.8	8814.1	10154.9
MoS₂	0.12	881.4	1195.0	10576.9	12185.9
Galvanized	0.25	1836.3	2489.7	22035.2	25387.3

UNF — Fine Thread — 12 TPI

Stress area: 1.315 in² · Proof load: 97,310 lbs · Clamp load (75%): 72,982 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	1672.5	2267.6	20070.2	23123.4
Oiled	0.15	1254.4	1700.7	15052.6	17342.5
Zinc Plated	0.18	1505.3	2040.9	18063.2	20811.0
Waxed	0.1	836.3	1133.9	10035.1	11561.7
MoS₂	0.12	1003.5	1360.6	12042.1	13874.0
Galvanized	0.25	2090.6	2834.5	25087.7	28904.2

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 734.5 ft·lbs (waxed) to 1836.3 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 × 74,000 psi × 1.155 in² = 64,102 lbs

Step 2 — Torque (dry): T = 0.20 × 1.375 in × 64,102 lbs ÷ 12 = 1469.0 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 5

Same as Grade 5 but with 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"

Grade5

Diameter1.375" (34.92 mm)

TPI (UNC)6

Tensile105,000 psi

Yield81,000 psi

Proof74,000 psi

1-3/8" Grade 5 Torque Spec