M8 Grade 4.6 Torque Specification

Torque Values by Surface Condition

Stress area: 36.61 mm² · Proof load: 8,237 N · Clamp load (75%): 6,178 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	9.9	7.3	87.6	101.0
Oiled	0.15	7.4	5.5	65.5	75.5
Zinc Plated	0.18	8.9	6.6	78.8	90.8
Waxed	0.1	4.9	3.6	43.4	50.0
MoS₂	0.12	5.9	4.4	52.2	60.2
Galvanized	0.25	12.4	9.1	109.7	126.4

Stress area: 39.17 mm² · Proof load: 8,813 N · Clamp load (75%): 6,610 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	10.6	7.8	93.8	108.1
Oiled	0.15	7.9	5.8	69.9	80.6
Zinc Plated	0.18	9.5	7.0	84.1	96.9
Waxed	0.1	5.3	3.9	46.9	54.0
MoS₂	0.12	6.3	4.6	55.8	64.2
Galvanized	0.25	13.2	9.7	116.8	134.6

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 225 MPa × 36.61 mm² = 6,178 N

Step 2 — Torque (dry): T = 0.20 × 0.0080 m × 6,178 N = 9.9 N·m

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

Non-critical assemblies, light-duty applications, general-purpose hardware where high strength is not required

• 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.

SizeM8

Class4.6

Diameter8 mm

Pitch (coarse)1.25 mm

Tensile400 MPa

Yield240 MPa

Proof225 MPa