M56 Grade 12.9 Torque Specification

Torque Values by Surface Condition

Stress area: 2030.0 mm² · Proof load: 1,969,100 N · Clamp load (75%): 1,476,825 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	16540.4	12199.6	146394.9	168665.8
Oiled	0.15	12405.3	9149.7	109796.2	126499.3
Zinc Plated	0.18	14886.4	10979.6	131755.8	151799.6
Waxed	0.1	8270.2	6099.8	73197.5	84332.9
MoS₂	0.12	9924.3	7319.8	87837.5	101200.1
Galvanized	0.25	20675.5	15249.5	182993.7	210832.2

Stress area: 2120.0 mm² · Proof load: 2,056,400 N · Clamp load (75%): 1,542,300 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	17273.8	12740.5	152886.1	176144.4
Oiled	0.15	12955.3	9555.3	114664.1	132107.8
Zinc Plated	0.18	15546.4	11466.4	137597.3	158529.8
Waxed	0.1	8636.9	6370.2	76443.0	88072.2
MoS₂	0.12	10364.3	7644.3	91731.8	105686.8
Galvanized	0.25	21592.2	15925.6	191107.2	220180.0

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 970 MPa × 2030.0 mm² = 1,476,825 N

Step 2 — Torque (dry): T = 0.20 × 0.0560 m × 1,476,825 N = 16540.4 N·m

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

Socket head cap screws, racing/motorsport, aerospace, maximum strength applications — highest standard grade

• 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

Class12.9

Diameter56 mm

Pitch (coarse)5.5 mm

Tensile1220 MPa

Yield1100 MPa

Proof970 MPa