3/8" Grade 5 Bolt Torque: 30.9 ft·lbs / 41.9 N·m

Torque Values by Surface Condition

UNC — Coarse Thread — 16 TPI

Stress area: 0.0775 in² · Proof load: 6,588 lbs · Clamp load (75%): 4,941 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	30.9	41.9	370.5	426.9
Oiled	0.15	23.2	31.5	277.9	320.2
Zinc Plated	0.18	27.8	37.7	333.5	384.2
Waxed	0.1	15.4	20.9	185.3	213.5
MoS₂	0.12	18.5	25.1	222.3	256.1
Galvanized	0.25	38.6	52.3	463.2	533.6

UNF — Fine Thread — 24 TPI

Stress area: 0.0878 in² · Proof load: 7,463 lbs · Clamp load (75%): 5,597 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	35.0	47.5	419.8	483.7
Oiled	0.15	26.2	35.5	314.8	362.7
Zinc Plated	0.18	31.5	42.7	377.8	435.3
Waxed	0.1	17.5	23.7	209.9	241.8
MoS₂	0.12	21.0	28.5	251.9	290.2
Galvanized	0.25	43.7	59.2	524.7	604.6

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 15.4 ft·lbs (waxed) to 38.6 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 × 0.0775 in² = 4,941 lbs

Step 2 — Torque (dry): T = 0.20 × 0.375 in × 4,941 lbs ÷ 12 = 30.9 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

Size3/8"

Grade5

Diameter0.375" (9.52 mm)

TPI (UNC)16

Tensile120,000 psi

Yield92,000 psi

Proof85,000 psi

3/8" Grade 5 Torque Spec