M18 Grade 5.8 Torque Specification

Torque Values by Surface Condition

Stress area: 192.47 mm² · Proof load: 73,139 N · Clamp load (75%): 54,854 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	197.5	145.7	1748.0	2013.9
Oiled	0.15	148.1	109.2	1310.8	1510.2
Zinc Plated	0.18	177.7	131.1	1572.8	1812.0
Waxed	0.1	98.7	72.8	873.6	1006.5
MoS₂	0.12	118.5	87.4	1048.8	1208.4
Galvanized	0.25	246.8	182.0	2184.4	2516.7

Stress area: 216.23 mm² · Proof load: 82,167 N · Clamp load (75%): 61,626 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	221.9	163.7	1964.0	2262.8
Oiled	0.15	166.4	122.7	1472.8	1696.8
Zinc Plated	0.18	199.7	147.3	1767.5	2036.4
Waxed	0.1	110.9	81.8	981.5	1130.9
MoS₂	0.12	133.1	98.2	1178.0	1357.2
Galvanized	0.25	277.3	204.5	2454.3	2827.7

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 380 MPa × 192.47 mm² = 54,854 N

Step 2 — Torque (dry): T = 0.20 × 0.0180 m × 54,854 N = 197.5 N·m

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

General industrial fastening, equipment mounting, moderate structural loads

• 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.

SizeM18

Class5.8

Diameter18 mm

Pitch (coarse)2.5 mm

Tensile520 MPa

Yield420 MPa

Proof380 MPa