M33 Grade 5.8 Torque Specification

Torque Values by Surface Condition

Stress area: 693.55 mm² · Proof load: 263,549 N · Clamp load (75%): 197,662 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1304.6	962.2	11546.7	13303.3
Oiled	0.15	978.4	721.6	8659.6	9976.9
Zinc Plated	0.18	1174.1	866.0	10391.7	11972.5
Waxed	0.1	652.3	481.1	5773.3	6651.6
MoS₂	0.12	782.7	577.3	6927.5	7981.3
Galvanized	0.25	1630.7	1202.7	14432.9	16628.6

Stress area: 760.85 mm² · Proof load: 289,123 N · Clamp load (75%): 216,842 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1431.2	1055.6	12667.2	14594.2
Oiled	0.15	1073.4	791.7	9500.4	10945.7
Zinc Plated	0.18	1288.0	950.0	11399.8	13134.0
Waxed	0.1	715.6	527.8	6333.6	7297.1
MoS₂	0.12	858.7	633.3	7600.1	8756.3
Galvanized	0.25	1788.9	1319.4	15833.1	18241.8

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 380 MPa × 693.55 mm² = 197,662 N

Step 2 — Torque (dry): T = 0.20 × 0.0330 m × 197,662 N = 1304.6 N·m

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

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.

SizeM33

Class5.8

Diameter33 mm

Pitch (coarse)3.5 mm

Tensile520 MPa

Yield420 MPa

Proof380 MPa