M45 Grade 8.8 Torque Specification

Torque Values by Surface Condition

Stress area: 1306.09 mm² · Proof load: 757,532 N · Clamp load (75%): 568,149 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	5113.3	3771.4	45256.5	52141.3
Oiled	0.15	3835.0	2828.6	33942.6	39106.3
Zinc Plated	0.18	4602.0	3394.3	40731.2	46927.5
Waxed	0.1	2556.7	1885.7	22628.7	26071.2
MoS₂	0.12	3068.0	2262.8	27154.1	31285.0
Galvanized	0.25	6391.7	4714.3	56571.3	65177.4

Stress area: 1397.15 mm² · Proof load: 810,347 N · Clamp load (75%): 607,760 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	5469.8	4034.3	48411.8	55776.6
Oiled	0.15	4102.4	3025.8	36309.3	41833.0
Zinc Plated	0.18	4922.9	3630.9	43571.4	50199.8
Waxed	0.1	2734.9	2017.2	24205.9	27888.3
MoS₂	0.12	3281.9	2420.6	29047.3	33466.2
Galvanized	0.25	6837.3	5042.9	60515.2	69721.3

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 580 MPa × 1306.09 mm² = 568,149 N

Step 2 — Torque (dry): T = 0.20 × 0.0450 m × 568,149 N = 5113.3 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.

SizeM45

Class8.8

Diameter45 mm

Pitch (coarse)4.5 mm

Tensile800 MPa

Yield640 MPa

Proof580 MPa