1/2" Grade 5 Bolt Torque: 75.4 ft·lbs / 102.2 N·m

Torque Values by Surface Condition

UNC — Coarse Thread — 13 TPI

Stress area: 0.1419 in² · Proof load: 12,062 lbs · Clamp load (75%): 9,046 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	75.4	102.2	904.6	1042.2
Oiled	0.15	56.5	76.6	678.5	781.7
Zinc Plated	0.18	67.8	91.9	814.2	938.0
Waxed	0.1	37.7	51.1	452.3	521.1
MoS₂	0.12	45.2	61.3	542.8	625.3
Galvanized	0.25	94.2	127.7	1130.8	1302.8

UNF — Fine Thread — 20 TPI

Stress area: 0.1599 in² · Proof load: 13,591 lbs · Clamp load (75%): 10,194 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	85.0	115.2	1019.4	1174.4
Oiled	0.15	63.7	86.4	764.5	880.8
Zinc Plated	0.18	76.5	103.7	917.4	1057.0
Waxed	0.1	42.5	57.6	509.7	587.2
MoS₂	0.12	51.0	69.1	611.6	704.7
Galvanized	0.25	106.2	144.0	1274.2	1468.0

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 37.7 ft·lbs (waxed) to 94.2 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 × 0.1419 in² = 9,046 lbs

Step 2 — Torque (dry): T = 0.20 × 0.5 in × 9,046 lbs ÷ 12 = 75.4 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

Size1/2"

Grade5

Diameter0.5" (12.70 mm)

TPI (UNC)13

Tensile120,000 psi

Yield92,000 psi

Proof85,000 psi

1/2" Grade 5 Torque Spec