M4 Grade 12.9 Torque Specification

Torque Values by Surface Condition

Stress area: 8.78 mm² · Proof load: 8,517 N · Clamp load (75%): 6,387 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	5.1	3.8	45.1	52.0
Oiled	0.15	3.8	2.8	33.6	38.7
Zinc Plated	0.18	4.6	3.4	40.7	46.9
Waxed	0.1	2.6	1.9	23.0	26.5
MoS₂	0.12	3.1	2.3	27.4	31.6
Galvanized	0.25	6.4	4.7	56.6	65.3

Stress area: 9.79 mm² · Proof load: 9,496 N · Clamp load (75%): 7,122 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	5.7	4.2	50.4	58.1
Oiled	0.15	4.3	3.2	38.1	43.8
Zinc Plated	0.18	5.1	3.8	45.1	52.0
Waxed	0.1	2.8	2.1	24.8	28.6
MoS₂	0.12	3.4	2.5	30.1	34.7
Galvanized	0.25	7.1	5.2	62.8	72.4

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 970 MPa × 8.78 mm² = 6,387 N

Step 2 — Torque (dry): T = 0.20 × 0.0040 m × 6,387 N = 5.1 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.

SizeM4

Class12.9

Diameter4 mm

Pitch (coarse)0.7 mm

Tensile1220 MPa

Yield1100 MPa

Proof970 MPa