1/4" Grade 5 Bolt Torque: 8.4 ft·lbs / 11.4 N·m

Torque Values by Surface Condition

UNC — Coarse Thread — 20 TPI

Stress area: 0.0318 in² · Proof load: 2,703 lbs · Clamp load (75%): 2,027 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	8.45	11.4	101.4	116.8
Oiled	0.15	6.34	8.59	76.0	87.6
Zinc Plated	0.18	7.60	10.3	91.2	105.1
Waxed	0.1	4.22	5.73	50.7	58.4
MoS₂	0.12	5.07	6.87	60.8	70.1
Galvanized	0.25	10.6	14.4	126.7	146.0

UNF — Fine Thread — 28 TPI

Stress area: 0.03637 in² · Proof load: 3,091 lbs · Clamp load (75%): 2,319 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	9.66	13.2	115.9	133.6
Oiled	0.15	7.25	9.82	86.9	100.2
Zinc Plated	0.18	8.69	11.8	104.3	120.2
Waxed	0.1	4.83	6.55	58.0	66.8
MoS₂	0.12	5.80	7.86	69.6	80.1
Galvanized	0.25	12.1	16.4	144.9	167.0

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 4.22 ft·lbs (waxed) to 10.6 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 × 0.0318 in² = 2,027 lbs

Step 2 — Torque (dry): T = 0.20 × 0.25 in × 2,027 lbs ÷ 12 = 8.4 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

Size1/4"

Grade5

Diameter0.25" (6.35 mm)

TPI (UNC)20

Tensile120,000 psi

Yield92,000 psi

Proof85,000 psi

1/4" Grade 5 Torque Spec