3/4" Grade 2 Bolt Torque: 172.2 ft·lbs / 233.5 N·m

Torque Values by Surface Condition

UNC — Coarse Thread — 10 TPI

Stress area: 0.334 in² · Proof load: 18,370 lbs · Clamp load (75%): 13,778 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	172.2	233.5	2066.6	2381.0
Oiled	0.15	129.2	175.2	1550.0	1785.8
Zinc Plated	0.18	155.0	210.2	1860.0	2142.9
Waxed	0.1	86.1	116.7	1033.3	1190.5
MoS₂	0.12	103.3	140.1	1240.0	1428.6
Galvanized	0.25	215.3	291.9	2583.3	2976.3

UNF — Fine Thread — 16 TPI

Stress area: 0.373 in² · Proof load: 20,515 lbs · Clamp load (75%): 15,386 lbs

Surface Condition	K Factor	ft·lbs	N·m	in·lbs	kgf·cm
Plain/Dry	0.2	192.3	260.7	2307.9	2659.0
Oiled	0.15	144.2	195.5	1731.0	1994.3
Zinc Plated	0.18	173.1	234.7	2077.1	2393.1
Waxed	0.1	96.2	130.4	1154.0	1329.5
MoS₂	0.12	115.4	156.5	1384.8	1595.4
Galvanized	0.25	240.4	325.9	2884.9	3323.8

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 86.1 ft·lbs (waxed) to 215.3 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 × 0.334 in² = 13,778 lbs

Step 2 — Torque (dry): T = 0.20 × 0.75 in × 13,778 lbs ÷ 12 = 172.2 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

Size3/4"

Grade2

Diameter0.75" (19.05 mm)

TPI (UNC)10

Tensile74,000 psi

Yield57,000 psi

Proof55,000 psi

3/4" Grade 2 Torque Spec