1/4" Grade 2 Bolt Torque: 5.5 ft·lbs / 7.5 N·m

Torque Values by Surface Condition

UNC — Coarse Thread — 20 TPI

Stress area: 0.0318 in² · Proof load: 1,749 lbs · Clamp load (75%): 1,312 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	5.47	7.41	65.6	75.6
Oiled	0.15	4.10	5.56	49.2	56.7
Zinc Plated	0.18	4.92	6.67	59.0	68.0
Waxed	0.1	2.73	3.71	32.8	37.8
MoS₂	0.12	3.28	4.45	39.4	45.3
Galvanized	0.25	6.83	9.26	82.0	94.5

UNF — Fine Thread — 28 TPI

Stress area: 0.03637 in² · Proof load: 2,000 lbs · Clamp load (75%): 1,500 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	6.25	8.48	75.0	86.4
Oiled	0.15	4.69	6.36	56.3	64.8
Zinc Plated	0.18	5.63	7.63	67.5	77.8
Waxed	0.1	3.13	4.24	37.5	43.2
MoS₂	0.12	3.75	5.09	45.0	51.9
Galvanized	0.25	7.81	10.6	93.8	108.0

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 2.73 ft·lbs (waxed) to 6.83 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 × 0.0318 in² = 1,312 lbs

Step 2 — Torque (dry): T = 0.20 × 0.25 in × 1,312 lbs ÷ 12 = 5.5 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

Size1/4"

Grade2

Diameter0.25" (6.35 mm)

TPI (UNC)20

Tensile74,000 psi

Yield57,000 psi

Proof55,000 psi

1/4" Grade 2 Torque Spec