M24 Grade 8.8 Torque Specification

Torque Values by Surface Condition

Stress area: 352.5 mm² · Proof load: 204,450 N · Clamp load (75%): 153,338 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	736.0	542.8	6514.2	7505.1
Oiled	0.15	552.0	407.1	4885.6	5628.9
Zinc Plated	0.18	662.4	488.6	5862.7	6754.6
Waxed	0.1	368.0	271.4	3257.1	3752.6
MoS₂	0.12	441.6	325.7	3908.5	4503.1
Galvanized	0.25	920.0	678.6	8142.7	9381.4

Stress area: 384.42 mm² · Proof load: 222,964 N · Clamp load (75%): 167,223 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	802.7	592.0	7104.5	8185.3
Oiled	0.15	602.0	444.0	5328.2	6138.7
Zinc Plated	0.18	722.4	532.8	6393.8	7366.5
Waxed	0.1	401.3	296.0	3551.8	4092.1
MoS₂	0.12	481.6	355.2	4262.5	4911.0
Galvanized	0.25	1003.3	740.0	8880.0	10230.9

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 580 MPa × 352.5 mm² = 153,338 N

Step 2 — Torque (dry): T = 0.20 × 0.0240 m × 153,338 N = 736.0 N·m

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

Automotive engines, structural connections, high-strength machinery, flanged joints — the most common high-strength 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.

SizeM24

Class8.8

Diameter24 mm

Pitch (coarse)3.0 mm

Tensile800 MPa

Yield640 MPa

Proof580 MPa