M20 Grade 12.9 Torque Specification

Torque Values by Surface Condition

Stress area: 244.79 mm² · Proof load: 237,446 N · Clamp load (75%): 178,085 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	712.3	525.4	6304.4	7263.5
Oiled	0.15	534.3	394.1	4729.0	5448.4
Zinc Plated	0.18	641.1	472.9	5674.2	6537.4
Waxed	0.1	356.2	262.7	3152.6	3632.2
MoS₂	0.12	427.4	315.2	3782.8	4358.3
Galvanized	0.25	890.4	656.7	7880.7	9079.6

Stress area: 271.5 mm² · Proof load: 263,355 N · Clamp load (75%): 197,516 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	790.1	582.7	6993.0	8056.8
Oiled	0.15	592.5	437.0	5244.1	6041.8
Zinc Plated	0.18	711.1	524.5	6293.8	7251.2
Waxed	0.1	395.0	291.3	3496.0	4027.9
MoS₂	0.12	474.0	349.6	4195.3	4833.5
Galvanized	0.25	987.6	728.4	8741.0	10070.8

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 970 MPa × 244.79 mm² = 178,085 N

Step 2 — Torque (dry): T = 0.20 × 0.0200 m × 178,085 N = 712.3 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.

SizeM20

Class12.9

Diameter20 mm

Pitch (coarse)2.5 mm

Tensile1220 MPa

Yield1100 MPa

Proof970 MPa