M48 Grade 8.8 Torque Specification

Torque Values by Surface Condition

Stress area: 1473.19 mm² · Proof load: 854,450 N · Clamp load (75%): 640,838 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	6152.0	4537.5	54449.8	62733.2
Oiled	0.15	4614.0	3403.1	40837.4	47049.9
Zinc Plated	0.18	5536.8	4083.7	49004.8	56459.9
Waxed	0.1	3076.0	2268.7	27224.9	31366.6
MoS₂	0.12	3691.2	2722.5	32669.9	37639.9
Galvanized	0.25	7690.1	5671.9	68063.2	78417.5

Stress area: 1602.9 mm² · Proof load: 929,682 N · Clamp load (75%): 697,262 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	6693.7	4937.0	59244.3	68257.0
Oiled	0.15	5020.3	3702.8	44433.4	51193.0
Zinc Plated	0.18	6024.3	4443.3	53319.6	61431.0
Waxed	0.1	3346.9	2468.5	29622.6	34129.0
MoS₂	0.12	4016.2	2962.2	35546.4	40954.0
Galvanized	0.25	8367.1	6171.3	74055.1	85321.0

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 580 MPa × 1473.19 mm² = 640,838 N

Step 2 — Torque (dry): T = 0.20 × 0.0480 m × 640,838 N = 6152.0 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.

SizeM48

Class8.8

Diameter48 mm

Pitch (coarse)5.0 mm

Tensile800 MPa

Yield640 MPa

Proof580 MPa