M52 Grade 5.6 Torque Specification

Torque Values by Surface Condition

Stress area: 1757.73 mm² · Proof load: 492,164 N · Clamp load (75%): 369,123 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	3838.9	2831.4	33977.1	39146.0
Oiled	0.15	2879.2	2123.6	25483.1	29359.8
Zinc Plated	0.18	3455.0	2548.3	30579.3	35231.3
Waxed	0.1	1919.4	1415.7	16988.1	19572.5
MoS₂	0.12	2303.3	1698.8	20385.9	23487.2
Galvanized	0.25	4798.6	3539.3	42471.2	48932.3

Stress area: 1828.6 mm² · Proof load: 512,008 N · Clamp load (75%): 384,006 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	3993.7	2945.6	35347.2	40724.6
Oiled	0.15	2995.2	2209.1	26509.8	30542.7
Zinc Plated	0.18	3594.3	2651.0	31812.3	36651.8
Waxed	0.1	1996.8	1472.8	17673.2	20361.8
MoS₂	0.12	2396.2	1767.3	21208.2	24434.5
Galvanized	0.25	4992.1	3682.0	44183.8	50905.4

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 280 MPa × 1757.73 mm² = 369,123 N

Step 2 — Torque (dry): T = 0.20 × 0.0520 m × 369,123 N = 3838.9 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.

SizeM52

Class5.6

Diameter52 mm

Pitch (coarse)5.0 mm

Tensile500 MPa

Yield300 MPa

Proof280 MPa