M52 Grade 12.9 Torque Specification

Torque Values by Surface Condition

Stress area: 1757.73 mm² · Proof load: 1,704,998 N · Clamp load (75%): 1,278,749 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	13299.0	9808.8	117706.1	135612.6
Oiled	0.15	9974.2	7356.6	88279.2	101708.9
Zinc Plated	0.18	11969.1	8828.0	105935.5	122051.3
Waxed	0.1	6649.5	4904.4	58853.1	67806.3
MoS₂	0.12	7979.4	5885.3	70623.7	81367.5
Galvanized	0.25	16623.7	12261.0	147132.2	169515.2

Stress area: 1828.6 mm² · Proof load: 1,773,742 N · Clamp load (75%): 1,330,306 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	13835.2	10204.3	122451.9	141080.3
Oiled	0.15	10376.4	7653.2	91838.9	105810.2
Zinc Plated	0.18	12451.7	9183.9	110206.9	126972.5
Waxed	0.1	6917.6	5102.2	61225.9	70540.2
MoS₂	0.12	8301.1	6122.6	73471.0	84648.0
Galvanized	0.25	17294.0	12755.4	153064.9	176350.4

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 970 MPa × 1757.73 mm² = 1,278,749 N

Step 2 — Torque (dry): T = 0.20 × 0.0520 m × 1,278,749 N = 13299.0 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.

SizeM52

Class12.9

Diameter52 mm

Pitch (coarse)5.0 mm

Tensile1220 MPa

Yield1100 MPa

Proof970 MPa