M52 Grade 10.9 Torque Specification

Torque Values by Surface Condition

Stress area: 1757.73 mm² · Proof load: 1,458,916 N · Clamp load (75%): 1,094,187 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	11379.5	8393.1	100717.1	116039.0
Oiled	0.15	8534.7	6294.9	75538.5	87030.0
Zinc Plated	0.18	10241.6	7553.8	90645.8	104435.6
Waxed	0.1	5689.8	4196.6	50359.0	58020.0
MoS₂	0.12	6827.7	5035.9	60430.3	69623.4
Galvanized	0.25	14224.4	10491.4	125896.6	145049.1

Stress area: 1828.6 mm² · Proof load: 1,517,738 N · Clamp load (75%): 1,138,304 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	11838.4	8731.6	104778.7	120718.5
Oiled	0.15	8878.8	6548.7	78584.0	90538.9
Zinc Plated	0.18	10654.5	7858.4	94300.3	108646.1
Waxed	0.1	5919.2	4365.8	52389.4	60359.3
MoS₂	0.12	7103.0	5238.9	62866.9	72430.7
Galvanized	0.25	14797.9	10914.4	130972.5	150897.1

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 830 MPa × 1757.73 mm² = 1,094,187 N

Step 2 — Torque (dry): T = 0.20 × 0.0520 m × 1,094,187 N = 11379.5 N·m

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

Structural steel (equivalent to ASTM A490), heavy machinery, high-strength critical joints, pressure vessels

• 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

Class10.9

Diameter52 mm

Pitch (coarse)5.0 mm

Tensile1040 MPa

Yield940 MPa

Proof830 MPa