M4 Grade 10.9 Torque Specification

Torque Values by Surface Condition

Stress area: 8.78 mm² · Proof load: 7,287 N · Clamp load (75%): 5,466 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	4.4	3.2	38.9	44.9
Oiled	0.15	3.3	2.4	29.2	33.7
Zinc Plated	0.18	3.9	2.9	34.5	39.8
Waxed	0.1	2.2	1.6	19.5	22.4
MoS₂	0.12	2.6	1.9	23.0	26.5
Galvanized	0.25	5.5	4.1	48.7	56.1

Stress area: 9.79 mm² · Proof load: 8,126 N · Clamp load (75%): 6,094 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	4.9	3.6	43.4	50.0
Oiled	0.15	3.7	2.7	32.7	37.7
Zinc Plated	0.18	4.4	3.2	38.9	44.9
Waxed	0.1	2.4	1.8	21.2	24.5
MoS₂	0.12	2.9	2.1	25.7	29.6
Galvanized	0.25	6.1	4.5	54.0	62.2

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 830 MPa × 8.78 mm² = 5,466 N

Step 2 — Torque (dry): T = 0.20 × 0.0040 m × 5,466 N = 4.4 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.

SizeM4

Class10.9

Diameter4 mm

Pitch (coarse)0.7 mm

Tensile1040 MPa

Yield940 MPa

Proof830 MPa