M39 Grade 5.6 Torque Specification

Torque Values by Surface Condition

Stress area: 976.0 mm² · Proof load: 273,280 N · Clamp load (75%): 204,960 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1598.7	1179.1	14149.7	16302.3
Oiled	0.15	1199.0	884.3	10612.0	12226.4
Zinc Plated	0.18	1438.8	1061.2	12734.5	14671.7
Waxed	0.1	799.3	589.5	7074.4	8150.6
MoS₂	0.12	959.2	707.5	8489.6	9781.2
Galvanized	0.25	1998.4	1473.9	17687.3	20378.1

Stress area: 1028.4 mm² · Proof load: 287,952 N · Clamp load (75%): 215,964 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1684.5	1242.4	14909.1	17177.2
Oiled	0.15	1263.4	931.8	11182.0	12883.1
Zinc Plated	0.18	1516.1	1118.2	13418.6	15460.0
Waxed	0.1	842.3	621.2	7455.0	8589.1
MoS₂	0.12	1010.7	745.5	8945.5	10306.3
Galvanized	0.25	2105.6	1553.0	18636.1	21471.2

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 280 MPa × 976.0 mm² = 204,960 N

Step 2 — Torque (dry): T = 0.20 × 0.0390 m × 204,960 N = 1598.7 N·m

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

Moderate-duty industrial applications, machinery guards, medium-strength connections

• 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

Class5.6

Diameter39 mm

Pitch (coarse)4.0 mm

Tensile500 MPa

Yield300 MPa

Proof280 MPa