M56 Grade 10.9 Torque Specification

Torque Values by Surface Condition

Stress area: 2030.0 mm² · Proof load: 1,684,900 N · Clamp load (75%): 1,263,675 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	14153.2	10438.9	125266.4	144323.0
Oiled	0.15	10614.9	7829.1	93949.8	108242.3
Zinc Plated	0.18	12737.8	9394.9	112739.1	129889.9
Waxed	0.1	7076.6	5219.4	62633.2	72161.5
MoS₂	0.12	8491.9	6263.3	75159.7	86593.6
Galvanized	0.25	17691.5	13048.6	156583.0	180403.8

Stress area: 2120.0 mm² · Proof load: 1,759,600 N · Clamp load (75%): 1,319,700 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	14780.6	10901.6	130819.4	150720.7
Oiled	0.15	11085.5	8176.2	98115.0	113041.1
Zinc Plated	0.18	13302.6	9811.5	117738.0	135649.3
Waxed	0.1	7390.3	5450.8	65409.7	75360.4
MoS₂	0.12	8868.4	6541.0	78492.0	90432.8
Galvanized	0.25	18475.8	13627.0	163524.7	188401.4

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 830 MPa × 2030.0 mm² = 1,263,675 N

Step 2 — Torque (dry): T = 0.20 × 0.0560 m × 1,263,675 N = 14153.2 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.

SizeM56

Class10.9

Diameter56 mm

Pitch (coarse)5.5 mm

Tensile1040 MPa

Yield940 MPa

Proof830 MPa