M27 Grade 8.8 Torque Specification

Torque Values by Surface Condition

Stress area: 459.41 mm² · Proof load: 266,458 N · Clamp load (75%): 199,843 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1079.2	796.0	9551.7	11004.8
Oiled	0.15	809.4	597.0	7163.8	8253.6
Zinc Plated	0.18	971.2	716.3	8595.8	9903.5
Waxed	0.1	539.6	398.0	4775.9	5502.4
MoS₂	0.12	647.5	477.6	5730.9	6602.7
Galvanized	0.25	1348.9	994.9	11938.8	13755.0

Stress area: 496.18 mm² · Proof load: 287,784 N · Clamp load (75%): 215,838 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1165.5	859.6	10315.5	11884.8
Oiled	0.15	874.1	644.7	7736.4	8913.4
Zinc Plated	0.18	1049.0	773.7	9284.4	10696.9
Waxed	0.1	582.8	429.9	5158.2	5942.9
MoS₂	0.12	699.3	515.8	6189.3	7130.9
Galvanized	0.25	1456.9	1074.6	12894.7	14856.3

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 580 MPa × 459.41 mm² = 199,843 N

Step 2 — Torque (dry): T = 0.20 × 0.0270 m × 199,843 N = 1079.2 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.

SizeM27

Class8.8

Diameter27 mm

Pitch (coarse)3.0 mm

Tensile800 MPa

Yield640 MPa

Proof580 MPa