M42 Grade 5.8 Torque Specification

Torque Values by Surface Condition

Stress area: 1120.9 mm² · Proof load: 425,942 N · Clamp load (75%): 319,456 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	2683.4	1979.2	23750.1	27363.2
Oiled	0.15	2012.6	1484.4	17813.0	20522.9
Zinc Plated	0.18	2415.1	1781.3	21375.4	24627.3
Waxed	0.1	1341.7	989.6	11875.1	13681.6
MoS₂	0.12	1610.1	1187.5	14250.6	16418.5
Galvanized	0.25	3354.3	2474.0	29688.1	34204.5

Stress area: 1205.7 mm² · Proof load: 458,166 N · Clamp load (75%): 343,624 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	2886.4	2128.9	25546.8	29433.2
Oiled	0.15	2164.8	1596.7	19160.1	22074.9
Zinc Plated	0.18	2597.8	1916.0	22992.5	26490.3
Waxed	0.1	1443.2	1064.4	12773.4	14716.6
MoS₂	0.12	1731.9	1277.4	15328.6	17660.5
Galvanized	0.25	3608.1	2661.2	31934.4	36792.5

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 380 MPa × 1120.9 mm² = 319,456 N

Step 2 — Torque (dry): T = 0.20 × 0.0420 m × 319,456 N = 2683.4 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.

SizeM42

Class5.8

Diameter42 mm

Pitch (coarse)4.5 mm

Tensile520 MPa

Yield420 MPa

Proof380 MPa