M3 Grade 12.9 Torque Specification

Torque Values by Surface Condition

Stress area: 5.03 mm² · Proof load: 4,879 N · Clamp load (75%): 3,659 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	2.2	1.6	19.5	22.4
Oiled	0.15	1.6	1.2	14.2	16.3
Zinc Plated	0.18	2.0	1.5	17.7	20.4
Waxed	0.1	1.1	0.8	9.7	11.2
MoS₂	0.12	1.3	1.0	11.5	13.3
Galvanized	0.25	2.7	2.0	23.9	27.5

Stress area: 5.61 mm² · Proof load: 5,442 N · Clamp load (75%): 4,081 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	2.4	1.8	21.2	24.5
Oiled	0.15	1.8	1.3	15.9	18.4
Zinc Plated	0.18	2.2	1.6	19.5	22.4
Waxed	0.1	1.2	0.9	10.6	12.2
MoS₂	0.12	1.5	1.1	13.3	15.3
Galvanized	0.25	3.1	2.3	27.4	31.6

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 970 MPa × 5.03 mm² = 3,659 N

Step 2 — Torque (dry): T = 0.20 × 0.0030 m × 3,659 N = 2.2 N·m

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

Socket head cap screws, racing/motorsport, aerospace, maximum strength applications — highest standard grade

• 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

Class12.9

Diameter3 mm

Pitch (coarse)0.5 mm

Tensile1220 MPa

Yield1100 MPa

Proof970 MPa