M30 Grade 8.8 Torque Specification

Torque Values by Surface Condition

Stress area: 560.59 mm² · Proof load: 325,142 N · Clamp load (75%): 243,857 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1463.1	1079.1	12949.5	14919.5
Oiled	0.15	1097.4	809.4	9712.8	11190.4
Zinc Plated	0.18	1316.8	971.2	11654.7	13427.7
Waxed	0.1	731.6	539.6	6475.2	7460.3
MoS₂	0.12	877.9	647.5	7770.1	8952.1
Galvanized	0.25	1828.9	1348.9	16187.1	18649.7

Stress area: 621.2 mm² · Proof load: 360,296 N · Clamp load (75%): 270,222 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1621.3	1195.8	14349.7	16532.7
Oiled	0.15	1216.0	896.9	10762.5	12399.8
Zinc Plated	0.18	1459.2	1076.3	12915.0	14879.8
Waxed	0.1	810.7	597.9	7175.3	8266.9
MoS₂	0.12	972.8	717.5	8610.0	9919.8
Galvanized	0.25	2026.7	1494.8	17937.8	20666.7

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 580 MPa × 560.59 mm² = 243,857 N

Step 2 — Torque (dry): T = 0.20 × 0.0300 m × 243,857 N = 1463.1 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.

SizeM30

Class8.8

Diameter30 mm

Pitch (coarse)3.5 mm

Tensile800 MPa

Yield640 MPa

Proof580 MPa