M5 Grade 6.8 Torque Specification

Torque Values by Surface Condition

Stress area: 14.18 mm² · Proof load: 6,239 N · Clamp load (75%): 4,679 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	4.7	3.5	41.6	47.9
Oiled	0.15	3.5	2.6	31.0	35.7
Zinc Plated	0.18	4.2	3.1	37.2	42.8
Waxed	0.1	2.3	1.7	20.4	23.5
MoS₂	0.12	2.8	2.1	24.8	28.6
Galvanized	0.25	5.8	4.3	51.3	59.1

Stress area: 16.13 mm² · Proof load: 7,097 N · Clamp load (75%): 5,323 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	5.3	3.9	46.9	54.0
Oiled	0.15	4.0	3.0	35.4	40.8
Zinc Plated	0.18	4.8	3.5	42.5	48.9
Waxed	0.1	2.7	2.0	23.9	27.5
MoS₂	0.12	3.2	2.4	28.3	32.6
Galvanized	0.25	6.7	4.9	59.3	68.3

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 440 MPa × 14.18 mm² = 4,679 N

Step 2 — Torque (dry): T = 0.20 × 0.0050 m × 4,679 N = 4.7 N·m

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

Industrial machinery, agricultural equipment, elevated load requirements

• 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

Class6.8

Diameter5 mm

Pitch (coarse)0.8 mm

Tensile600 MPa

Yield480 MPa

Proof440 MPa