M42 Grade 12.9 Torque Specification

Torque Values by Surface Condition

Stress area: 1120.9 mm² · Proof load: 1,087,273 N · Clamp load (75%): 815,455 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	6849.8	5052.2	60625.9	69848.8
Oiled	0.15	5137.4	3789.2	45469.8	52387.1
Zinc Plated	0.18	6164.8	4546.9	54563.1	62863.7
Waxed	0.1	3424.9	2526.1	30312.9	34924.4
MoS₂	0.12	4109.9	3031.3	36375.7	41909.5
Galvanized	0.25	8562.3	6315.2	75782.8	87311.5

Stress area: 1205.7 mm² · Proof load: 1,169,529 N · Clamp load (75%): 877,147 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	7368.0	5434.4	65212.3	75133.0
Oiled	0.15	5526.0	4075.8	48909.2	56349.7
Zinc Plated	0.18	6631.2	4890.9	58691.1	67619.7
Waxed	0.1	3684.0	2717.2	32606.2	37566.5
MoS₂	0.12	4420.8	3260.6	39127.4	45079.8
Galvanized	0.25	9210.0	6792.9	81515.4	93916.2

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 970 MPa × 1120.9 mm² = 815,455 N

Step 2 — Torque (dry): T = 0.20 × 0.0420 m × 815,455 N = 6849.8 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.

SizeM42

Class12.9

Diameter42 mm

Pitch (coarse)4.5 mm

Tensile1220 MPa

Yield1100 MPa

Proof970 MPa