1/2" Grade 2 Bolt Torque: 48.8 ft·lbs / 66.2 N·m

Torque Values by Surface Condition

UNC — Coarse Thread — 13 TPI

Stress area: 0.1419 in² · Proof load: 7,804 lbs · Clamp load (75%): 5,853 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	48.8	66.2	585.3	674.4
Oiled	0.15	36.6	49.6	439.0	505.8
Zinc Plated	0.18	43.9	59.5	526.8	606.9
Waxed	0.1	24.4	33.1	292.7	337.2
MoS₂	0.12	29.3	39.7	351.2	404.6
Galvanized	0.25	61.0	82.7	731.7	843.0

UNF — Fine Thread — 20 TPI

Stress area: 0.1599 in² · Proof load: 8,794 lbs · Clamp load (75%): 6,596 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	55.0	74.6	659.6	759.9
Oiled	0.15	41.2	55.9	494.7	569.9
Zinc Plated	0.18	49.5	67.1	593.6	683.9
Waxed	0.1	27.5	37.3	329.8	380.0
MoS₂	0.12	33.0	44.7	395.8	456.0
Galvanized	0.25	68.7	93.1	824.5	949.9

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 24.4 ft·lbs (waxed) to 61.0 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 × 55,000 psi × 0.1419 in² = 5,853 lbs

Step 2 — Torque (dry): T = 0.20 × 0.5 in × 5,853 lbs ÷ 12 = 48.8 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

General-purpose, non-critical bolting. Most common ungraded hardware-store bolts.

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"

Grade2

Diameter0.5" (12.70 mm)

TPI (UNC)13

Tensile74,000 psi

Yield57,000 psi

Proof55,000 psi

1/2" Grade 2 Torque Spec