M14 Grade 8.8 Torque Specification

Torque Values by Surface Condition

Stress area: 115.44 mm² · Proof load: 66,955 N · Clamp load (75%): 50,216 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	140.6	103.7	1244.4	1433.7
Oiled	0.15	105.5	77.8	933.8	1075.8
Zinc Plated	0.18	126.5	93.3	1119.6	1289.9
Waxed	0.1	70.3	51.9	622.2	716.9
MoS₂	0.12	84.4	62.3	747.0	860.6
Galvanized	0.25	175.8	129.7	1556.0	1792.7

Stress area: 124.55 mm² · Proof load: 72,239 N · Clamp load (75%): 54,179 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	151.7	111.9	1342.7	1546.9
Oiled	0.15	113.8	83.9	1007.2	1160.4
Zinc Plated	0.18	136.5	100.7	1208.1	1391.9
Waxed	0.1	75.9	56.0	671.8	774.0
MoS₂	0.12	91.0	67.1	805.4	927.9
Galvanized	0.25	189.6	139.8	1678.1	1933.4

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 580 MPa × 115.44 mm² = 50,216 N

Step 2 — Torque (dry): T = 0.20 × 0.0140 m × 50,216 N = 140.6 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.

SizeM14

Class8.8

Diameter14 mm

Pitch (coarse)2.0 mm

Tensile800 MPa

Yield640 MPa

Proof580 MPa