3/4" Grade 5 Bolt Torque: 266.2 ft·lbs / 360.9 N·m

Torque Values by Surface Condition

UNC — Coarse Thread — 10 TPI

Stress area: 0.334 in² · Proof load: 28,390 lbs · Clamp load (75%): 21,292 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	266.2	360.9	3193.9	3679.7
Oiled	0.15	199.6	270.6	2395.4	2759.8
Zinc Plated	0.18	239.5	324.7	2874.5	3311.8
Waxed	0.1	133.1	180.5	1596.9	1839.9
MoS₂	0.12	159.7	216.5	1916.3	2207.8
Galvanized	0.25	332.7	451.1	3992.3	4599.7

UNF — Fine Thread — 16 TPI

Stress area: 0.373 in² · Proof load: 31,705 lbs · Clamp load (75%): 23,779 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	297.2	402.9	3566.8	4109.4
Oiled	0.15	222.9	302.2	2675.1	3082.1
Zinc Plated	0.18	267.5	362.7	3210.1	3698.5
Waxed	0.1	148.6	201.5	1783.4	2054.7
MoS₂	0.12	178.3	241.7	2140.1	2465.6
Galvanized	0.25	371.5	503.7	4458.5	5136.8

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 133.1 ft·lbs (waxed) to 332.7 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 × 85,000 psi × 0.334 in² = 21,292 lbs

Step 2 — Torque (dry): T = 0.20 × 0.75 in × 21,292 lbs ÷ 12 = 266.2 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

Automotive, agricultural equipment, general machinery — the most common high-strength SAE grade. Equivalent to ISO 8.8.

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

Size3/4"

Grade5

Diameter0.75" (19.05 mm)

TPI (UNC)10

Tensile120,000 psi

Yield92,000 psi

Proof85,000 psi

3/4" Grade 5 Torque Spec