M42 Grade 10.9 Torque Specification

Torque Values by Surface Condition

Stress area: 1120.9 mm² · Proof load: 930,347 N · Clamp load (75%): 697,760 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	5861.2	4323.0	51876.0	59767.8
Oiled	0.15	4395.9	3242.2	38907.0	44825.9
Zinc Plated	0.18	5275.1	3890.7	46688.6	53791.2
Waxed	0.1	2930.6	2161.5	25938.0	29883.9
MoS₂	0.12	3516.7	2593.8	31125.4	35860.5
Galvanized	0.25	7326.5	5403.7	64845.0	74709.8

Stress area: 1205.7 mm² · Proof load: 1,000,731 N · Clamp load (75%): 750,548 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	6304.6	4650.0	55800.4	64289.3
Oiled	0.15	4728.5	3487.6	41850.8	48217.5
Zinc Plated	0.18	5674.1	4185.0	50220.0	57859.9
Waxed	0.1	3152.3	2325.0	27900.2	32144.6
MoS₂	0.12	3782.8	2790.0	33480.6	38574.0
Galvanized	0.25	7880.8	5812.6	69751.0	80362.1

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 830 MPa × 1120.9 mm² = 697,760 N

Step 2 — Torque (dry): T = 0.20 × 0.0420 m × 697,760 N = 5861.2 N·m

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

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.

SizeM42

Class10.9

Diameter42 mm

Pitch (coarse)4.5 mm

Tensile1040 MPa

Yield940 MPa

Proof830 MPa