M36 Grade 8.8 Torque Specification

Torque Values by Surface Condition

Stress area: 816.72 mm² · Proof load: 473,698 N · Clamp load (75%): 355,273 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	2558.0	1886.7	22640.2	26084.4
Oiled	0.15	1918.5	1415.0	16980.2	19563.3
Zinc Plated	0.18	2302.2	1698.0	20376.2	23476.0
Waxed	0.1	1279.0	943.3	11320.1	13042.2
MoS₂	0.12	1534.8	1132.0	13584.1	15650.7
Galvanized	0.25	3197.5	2358.4	28300.3	32605.5

Stress area: 864.95 mm² · Proof load: 501,671 N · Clamp load (75%): 376,253 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	2709.0	1998.1	23976.7	27624.2
Oiled	0.15	2031.8	1498.6	17983.0	20718.7
Zinc Plated	0.18	2438.1	1798.2	21579.0	24861.8
Waxed	0.1	1354.5	999.0	11988.3	13812.1
MoS₂	0.12	1625.4	1198.8	14386.0	16574.5
Galvanized	0.25	3386.3	2497.6	29971.3	34530.8

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 580 MPa × 816.72 mm² = 355,273 N

Step 2 — Torque (dry): T = 0.20 × 0.0360 m × 355,273 N = 2558.0 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.

SizeM36

Class8.8

Diameter36 mm

Pitch (coarse)4.0 mm

Tensile800 MPa

Yield640 MPa

Proof580 MPa