M6 Grade 6.8 Torque Specification

Torque Values by Surface Condition

Stress area: 20.12 mm² · Proof load: 8,853 N · Clamp load (75%): 6,640 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	8.0	5.9	70.8	81.6
Oiled	0.15	6.0	4.4	53.1	61.2
Zinc Plated	0.18	7.2	5.3	63.7	73.4
Waxed	0.1	4.0	3.0	35.4	40.8
MoS₂	0.12	4.8	3.5	42.5	48.9
Galvanized	0.25	10.0	7.4	88.5	102.0

Stress area: 22.03 mm² · Proof load: 9,693 N · Clamp load (75%): 7,270 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	8.7	6.4	77.0	88.7
Oiled	0.15	6.5	4.8	57.5	66.3
Zinc Plated	0.18	7.9	5.8	69.9	80.6
Waxed	0.1	4.4	3.2	38.9	44.9
MoS₂	0.12	5.2	3.8	46.0	53.0
Galvanized	0.25	10.9	8.0	96.5	111.1

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 440 MPa × 20.12 mm² = 6,640 N

Step 2 — Torque (dry): T = 0.20 × 0.0060 m × 6,640 N = 8.0 N·m

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

Industrial machinery, agricultural equipment, elevated load requirements

• 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.

SizeM6

Class6.8

Diameter6 mm

Pitch (coarse)1.0 mm

Tensile600 MPa

Yield480 MPa

Proof440 MPa