M12 Grade 8.8 Torque Specification

Torque Values by Surface Condition

Stress area: 84.27 mm² · Proof load: 48,877 N · Clamp load (75%): 36,657 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	88.0	64.9	778.9	897.4
Oiled	0.15	66.0	48.7	584.1	673.0
Zinc Plated	0.18	79.2	58.4	701.0	807.6
Waxed	0.1	44.0	32.5	389.4	448.7
MoS₂	0.12	52.8	38.9	467.3	538.4
Galvanized	0.25	110.0	81.1	973.6	1121.7

Stress area: 92.07 mm² · Proof load: 53,401 N · Clamp load (75%): 40,050 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	96.1	70.9	850.6	980.0
Oiled	0.15	72.1	53.2	638.1	735.2
Zinc Plated	0.18	86.5	63.8	765.6	882.1
Waxed	0.1	48.1	35.5	425.7	490.5
MoS₂	0.12	57.7	42.6	510.7	588.4
Galvanized	0.25	120.2	88.7	1063.9	1225.7

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 580 MPa × 84.27 mm² = 36,657 N

Step 2 — Torque (dry): T = 0.20 × 0.0120 m × 36,657 N = 88.0 N·m

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

Automotive engines, structural connections, high-strength machinery, flanged joints — the most common high-strength grade

• 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.

SizeM12

Class8.8

Diameter12 mm

Pitch (coarse)1.75 mm

Tensile800 MPa

Yield640 MPa

Proof580 MPa