M8 Grade 4.8 Torque Specification

Torque Values by Surface Condition

Stress area: 36.61 mm² · Proof load: 11,349 N · Clamp load (75%): 8,512 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	13.6	10.0	120.4	138.7
Oiled	0.15	10.2	7.5	90.3	104.0
Zinc Plated	0.18	12.3	9.1	108.9	125.4
Waxed	0.1	6.8	5.0	60.2	69.3
MoS₂	0.12	8.2	6.0	72.6	83.6
Galvanized	0.25	17.0	12.5	150.5	173.4

Stress area: 39.17 mm² · Proof load: 12,143 N · Clamp load (75%): 9,107 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	14.6	10.8	129.2	148.9
Oiled	0.15	10.9	8.0	96.5	111.1
Zinc Plated	0.18	13.1	9.7	115.9	133.6
Waxed	0.1	7.3	5.4	64.6	74.4
MoS₂	0.12	8.7	6.4	77.0	88.7
Galvanized	0.25	18.2	13.4	161.1	185.6

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 310 MPa × 36.61 mm² = 8,512 N

Step 2 — Torque (dry): T = 0.20 × 0.0080 m × 8,512 N = 13.6 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.

SizeM8

Class4.8

Diameter8 mm

Pitch (coarse)1.25 mm

Tensile420 MPa

Yield340 MPa

Proof310 MPa