M16 Grade 8.8 Torque Specification

Torque Values by Surface Condition

Stress area: 156.67 mm² · Proof load: 90,869 N · Clamp load (75%): 68,151 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	218.1	160.9	1930.3	2224.0
Oiled	0.15	163.6	120.7	1448.0	1668.3
Zinc Plated	0.18	196.3	144.8	1737.4	2001.7
Waxed	0.1	109.0	80.4	964.7	1111.5
MoS₂	0.12	130.9	96.5	1158.6	1334.8
Galvanized	0.25	272.6	201.1	2412.7	2779.8

Stress area: 167.25 mm² · Proof load: 97,005 N · Clamp load (75%): 72,754 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	232.8	171.7	2060.5	2373.9
Oiled	0.15	174.6	128.8	1545.3	1780.4
Zinc Plated	0.18	209.5	154.5	1854.2	2136.3
Waxed	0.1	116.4	85.9	1030.2	1187.0
MoS₂	0.12	139.7	103.0	1236.4	1424.5
Galvanized	0.25	291.0	214.6	2575.6	2967.4

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 580 MPa × 156.67 mm² = 68,151 N

Step 2 — Torque (dry): T = 0.20 × 0.0160 m × 68,151 N = 218.1 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.

SizeM16

Class8.8

Diameter16 mm

Pitch (coarse)2.0 mm

Tensile800 MPa

Yield640 MPa

Proof580 MPa