M39 Grade 4.6 Torque Specification

Torque Values by Surface Condition

Stress area: 976.0 mm² · Proof load: 219,600 N · Clamp load (75%): 164,700 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1284.7	947.5	11370.6	13100.3
Oiled	0.15	963.5	710.6	8527.7	9825.0
Zinc Plated	0.18	1156.2	852.8	10233.2	11790.0
Waxed	0.1	642.3	473.7	5684.8	6549.7
MoS₂	0.12	770.8	568.5	6822.2	7860.0
Galvanized	0.25	1605.8	1184.4	14212.5	16374.7

Stress area: 1028.4 mm² · Proof load: 231,390 N · Clamp load (75%): 173,543 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1353.6	998.4	11980.4	13802.9
Oiled	0.15	1015.2	748.8	8985.3	10352.2
Zinc Plated	0.18	1218.3	898.6	10782.9	12423.2
Waxed	0.1	676.8	499.2	5990.2	6901.5
MoS₂	0.12	812.2	599.0	7188.6	8282.2
Galvanized	0.25	1692.0	1248.0	14975.5	17253.7

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 225 MPa × 976.0 mm² = 164,700 N

Step 2 — Torque (dry): T = 0.20 × 0.0390 m × 164,700 N = 1284.7 N·m

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

Non-critical assemblies, light-duty applications, general-purpose hardware where high strength is not required

• 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.

SizeM39

Class4.6

Diameter39 mm

Pitch (coarse)4.0 mm

Tensile400 MPa

Yield240 MPa

Proof225 MPa