M4 Grade 4.8 Torque Specification

Torque Values by Surface Condition

Stress area: 8.78 mm² · Proof load: 2,722 N · Clamp load (75%): 2,041 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1.6	1.2	14.2	16.3
Oiled	0.15	1.2	0.9	10.6	12.2
Zinc Plated	0.18	1.5	1.1	13.3	15.3
Waxed	0.1	0.8	0.6	7.1	8.2
MoS₂	0.12	1.0	0.7	8.9	10.2
Galvanized	0.25	2.0	1.5	17.7	20.4

Stress area: 9.79 mm² · Proof load: 3,035 N · Clamp load (75%): 2,276 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1.8	1.3	15.9	18.4
Oiled	0.15	1.4	1.0	12.4	14.3
Zinc Plated	0.18	1.6	1.2	14.2	16.3
Waxed	0.1	0.9	0.7	8.0	9.2
MoS₂	0.12	1.1	0.8	9.7	11.2
Galvanized	0.25	2.3	1.7	20.4	23.5

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 310 MPa × 8.78 mm² = 2,041 N

Step 2 — Torque (dry): T = 0.20 × 0.0040 m × 2,041 N = 1.6 N·m

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

Light structural connections, furniture assembly, non-load-bearing joints

• 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.

SizeM4

Class4.8

Diameter4 mm

Pitch (coarse)0.7 mm

Tensile420 MPa

Yield340 MPa

Proof310 MPa