5/16" Grade 2 Bolt Torque: 11.3 ft·lbs / 15.3 N·m

Torque Values by Surface Condition

UNC — Coarse Thread — 18 TPI

Stress area: 0.0524 in² · Proof load: 2,882 lbs · Clamp load (75%): 2,162 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	11.3	15.3	135.1	155.6
Oiled	0.15	8.44	11.4	101.3	116.7
Zinc Plated	0.18	10.1	13.7	121.6	140.1
Waxed	0.1	5.63	7.63	67.5	77.8
MoS₂	0.12	6.75	9.16	81.1	93.4
Galvanized	0.25	14.1	19.1	168.9	194.6

UNF — Fine Thread — 24 TPI

Stress area: 0.058 in² · Proof load: 3,190 lbs · Clamp load (75%): 2,392 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	12.5	16.9	149.5	172.3
Oiled	0.15	9.35	12.6	112.1	129.2
Zinc Plated	0.18	11.2	15.2	134.6	155.1
Waxed	0.1	6.23	8.45	74.8	86.1
MoS₂	0.12	7.48	10.2	89.7	103.4
Galvanized	0.25	15.6	21.2	186.9	215.3

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 5.63 ft·lbs (waxed) to 14.1 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 × 0.0524 in² = 2,162 lbs

Step 2 — Torque (dry): T = 0.20 × 0.3125 in × 2,162 lbs ÷ 12 = 11.3 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

Size5/16"

Grade2

Diameter0.3125" (7.94 mm)

TPI (UNC)18

Tensile74,000 psi

Yield57,000 psi

Proof55,000 psi

5/16" Grade 2 Torque Spec