M5 Grade 8.8 Torque Specification

Torque Values by Surface Condition

Stress area: 14.18 mm² · Proof load: 8,224 N · Clamp load (75%): 6,168 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	6.2	4.6	54.9	63.2
Oiled	0.15	4.6	3.4	40.7	46.9
Zinc Plated	0.18	5.6	4.1	49.6	57.1
Waxed	0.1	3.1	2.3	27.4	31.6
MoS₂	0.12	3.7	2.7	32.7	37.7
Galvanized	0.25	7.7	5.7	68.2	78.5

Stress area: 16.13 mm² · Proof load: 9,355 N · Clamp load (75%): 7,017 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	7.0	5.2	62.0	71.4
Oiled	0.15	5.3	3.9	46.9	54.0
Zinc Plated	0.18	6.3	4.6	55.8	64.2
Waxed	0.1	3.5	2.6	31.0	35.7
MoS₂	0.12	4.2	3.1	37.2	42.8
Galvanized	0.25	8.8	6.5	77.9	89.7

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 580 MPa × 14.18 mm² = 6,168 N

Step 2 — Torque (dry): T = 0.20 × 0.0050 m × 6,168 N = 6.2 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.

SizeM5

Class8.8

Diameter5 mm

Pitch (coarse)0.8 mm

Tensile800 MPa

Yield640 MPa

Proof580 MPa