M22 Grade 6.8 Torque Specification

Torque Values by Surface Condition

Stress area: 303.4 mm² · Proof load: 133,496 N · Clamp load (75%): 100,122 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	440.5	324.9	3898.8	4491.9
Oiled	0.15	330.4	243.7	2924.3	3369.2
Zinc Plated	0.18	396.5	292.4	3509.3	4043.2
Waxed	0.1	220.3	162.5	1949.8	2246.4
MoS₂	0.12	264.3	194.9	2339.3	2695.1
Galvanized	0.25	550.7	406.2	4874.1	5615.6

Stress area: 333.01 mm² · Proof load: 146,524 N · Clamp load (75%): 109,893 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	483.5	356.6	4279.3	4930.3
Oiled	0.15	362.6	267.4	3209.3	3697.5
Zinc Plated	0.18	435.2	321.0	3851.8	4437.8
Waxed	0.1	241.8	178.3	2140.1	2465.7
MoS₂	0.12	290.1	214.0	2567.6	2958.2
Galvanized	0.25	604.4	445.8	5349.4	6163.2

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 440 MPa × 303.4 mm² = 100,122 N

Step 2 — Torque (dry): T = 0.20 × 0.0220 m × 100,122 N = 440.5 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.

SizeM22

Class6.8

Diameter22 mm

Pitch (coarse)2.5 mm

Tensile600 MPa

Yield480 MPa

Proof440 MPa