M7 Grade 8.8 Torque Specification

Torque Values by Surface Condition

Stress area: 28.86 mm² · Proof load: 16,739 N · Clamp load (75%): 12,554 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	17.6	13.0	155.8	179.5
Oiled	0.15	13.2	9.7	116.8	134.6
Zinc Plated	0.18	15.8	11.7	139.8	161.1
Waxed	0.1	8.8	6.5	77.9	89.7
MoS₂	0.12	10.5	7.7	92.9	107.1
Galvanized	0.25	22.0	16.2	194.7	224.3

Stress area: 31.23 mm² · Proof load: 18,113 N · Clamp load (75%): 13,585 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	19.0	14.0	168.2	193.7
Oiled	0.15	14.3	10.5	126.6	145.8
Zinc Plated	0.18	17.1	12.6	151.3	174.4
Waxed	0.1	9.5	7.0	84.1	96.9
MoS₂	0.12	11.4	8.4	100.9	116.2
Galvanized	0.25	23.8	17.6	210.6	242.7

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 580 MPa × 28.86 mm² = 12,554 N

Step 2 — Torque (dry): T = 0.20 × 0.0070 m × 12,554 N = 17.6 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.

SizeM7

Class8.8

Diameter7 mm

Pitch (coarse)1.0 mm

Tensile800 MPa

Yield640 MPa

Proof580 MPa