M8 Grade 5.6 Torque Specification

Torque Values by Surface Condition

Stress area: 36.61 mm² · Proof load: 10,251 N · Clamp load (75%): 7,688 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	12.3	9.1	108.9	125.4
Oiled	0.15	9.2	6.8	81.4	93.8
Zinc Plated	0.18	11.1	8.2	98.2	113.2
Waxed	0.1	6.2	4.6	54.9	63.2
MoS₂	0.12	7.4	5.5	65.5	75.5
Galvanized	0.25	15.4	11.4	136.3	157.0

Stress area: 39.17 mm² · Proof load: 10,968 N · Clamp load (75%): 8,226 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	13.2	9.7	116.8	134.6
Oiled	0.15	9.9	7.3	87.6	101.0
Zinc Plated	0.18	11.8	8.7	104.4	120.3
Waxed	0.1	6.6	4.9	58.4	67.3
MoS₂	0.12	7.9	5.8	69.9	80.6
Galvanized	0.25	16.5	12.2	146.0	168.3

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 280 MPa × 36.61 mm² = 7,688 N

Step 2 — Torque (dry): T = 0.20 × 0.0080 m × 7,688 N = 12.3 N·m

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

Moderate-duty industrial applications, machinery guards, medium-strength connections

• 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

Class5.6

Diameter8 mm

Pitch (coarse)1.25 mm

Tensile500 MPa

Yield300 MPa

Proof280 MPa