M12 Grade 6.8 Torque Specification

Torque Values by Surface Condition

Stress area: 84.27 mm² · Proof load: 37,079 N · Clamp load (75%): 27,809 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	66.7	49.2	590.3	680.2
Oiled	0.15	50.1	37.0	443.4	510.9
Zinc Plated	0.18	60.1	44.3	531.9	612.9
Waxed	0.1	33.4	24.6	295.6	340.6
MoS₂	0.12	40.0	29.5	354.0	407.9
Galvanized	0.25	83.4	61.5	738.2	850.4

Stress area: 92.07 mm² · Proof load: 40,511 N · Clamp load (75%): 30,383 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	72.9	53.8	645.2	743.4
Oiled	0.15	54.7	40.3	484.1	557.8
Zinc Plated	0.18	65.6	48.4	580.6	668.9
Waxed	0.1	36.5	26.9	323.1	372.2
MoS₂	0.12	43.8	32.3	387.7	446.6
Galvanized	0.25	91.1	67.2	806.3	929.0

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 440 MPa × 84.27 mm² = 27,809 N

Step 2 — Torque (dry): T = 0.20 × 0.0120 m × 27,809 N = 66.7 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.

SizeM12

Class6.8

Diameter12 mm

Pitch (coarse)1.75 mm

Tensile600 MPa

Yield480 MPa

Proof440 MPa