M22 Grade 8.8 Torque Specification

Torque Values by Surface Condition

Stress area: 303.4 mm² · Proof load: 175,972 N · Clamp load (75%): 131,979 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	580.7	428.3	5139.6	5921.5
Oiled	0.15	435.5	321.2	3854.5	4440.9
Zinc Plated	0.18	522.6	385.4	4625.4	5329.1
Waxed	0.1	290.4	214.2	2570.3	2961.3
MoS₂	0.12	348.4	257.0	3083.6	3552.7
Galvanized	0.25	725.9	535.4	6424.8	7402.1

Stress area: 333.01 mm² · Proof load: 193,146 N · Clamp load (75%): 144,859 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	637.4	470.1	5641.5	6499.7
Oiled	0.15	478.0	352.6	4230.7	4874.3
Zinc Plated	0.18	573.6	423.1	5076.8	5849.1
Waxed	0.1	318.7	235.1	2820.7	3249.8
MoS₂	0.12	382.4	282.0	3384.5	3899.4
Galvanized	0.25	796.7	587.6	7051.4	8124.1

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 580 MPa × 303.4 mm² = 131,979 N

Step 2 — Torque (dry): T = 0.20 × 0.0220 m × 131,979 N = 580.7 N·m

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

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.

SizeM22

Class8.8

Diameter22 mm

Pitch (coarse)2.5 mm

Tensile800 MPa

Yield640 MPa

Proof580 MPa