M3 Grade 10.9 Torque Specification

Torque Values by Surface Condition

Stress area: 5.03 mm² · Proof load: 4,175 N · Clamp load (75%): 3,131 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1.9	1.4	16.8	19.4
Oiled	0.15	1.4	1.0	12.4	14.3
Zinc Plated	0.18	1.7	1.3	15.0	17.3
Waxed	0.1	0.9	0.7	8.0	9.2
MoS₂	0.12	1.1	0.8	9.7	11.2
Galvanized	0.25	2.3	1.7	20.4	23.5

Stress area: 5.61 mm² · Proof load: 4,656 N · Clamp load (75%): 3,492 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	2.1	1.5	18.6	21.4
Oiled	0.15	1.6	1.2	14.2	16.3
Zinc Plated	0.18	1.9	1.4	16.8	19.4
Waxed	0.1	1.0	0.7	8.9	10.2
MoS₂	0.12	1.3	1.0	11.5	13.3
Galvanized	0.25	2.6	1.9	23.0	26.5

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 830 MPa × 5.03 mm² = 3,131 N

Step 2 — Torque (dry): T = 0.20 × 0.0030 m × 3,131 N = 1.9 N·m

Proof stress per ISO 898-1:2013 Table 4. Stress area per ISO 898-1 Annex A. K-factor per VDI 2230.

Structural steel (equivalent to ASTM A490), heavy machinery, high-strength critical joints, pressure vessels

• Torque values are for standard hex bolts with ISO metric threads. 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 (e.g., VDI 2230).
• Re-used bolts may have altered friction characteristics. Inspect threads before reuse.

SizeM3

Class10.9

Diameter3 mm

Pitch (coarse)0.5 mm

Tensile1040 MPa

Yield940 MPa

Proof830 MPa