M30 Grade 6.8 Torque Specification

Torque Values by Surface Condition

Stress area: 560.59 mm² · Proof load: 246,660 N · Clamp load (75%): 184,995 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1110.0	818.7	9824.3	11318.9
Oiled	0.15	832.5	614.0	7368.2	8489.2
Zinc Plated	0.18	999.0	736.8	8841.9	10187.0
Waxed	0.1	555.0	409.3	4912.2	5659.4
MoS₂	0.12	666.0	491.2	5894.6	6791.3
Galvanized	0.25	1387.5	1023.4	12280.4	14148.6

Stress area: 621.2 mm² · Proof load: 273,328 N · Clamp load (75%): 204,996 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1230.0	907.2	10886.4	12542.6
Oiled	0.15	922.5	680.4	8164.8	9406.9
Zinc Plated	0.18	1107.0	816.5	9797.8	11288.3
Waxed	0.1	615.0	453.6	5443.2	6271.3
MoS₂	0.12	738.0	544.3	6531.9	7525.5
Galvanized	0.25	1537.5	1134.0	13608.0	15678.2

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 440 MPa × 560.59 mm² = 184,995 N

Step 2 — Torque (dry): T = 0.20 × 0.0300 m × 184,995 N = 1110.0 N·m

Proof stress per ISO 898-1:2013 Table 4. Stress area per ISO 898-1 Annex A. K-factor per VDI 2230.

Industrial machinery, agricultural equipment, elevated load requirements

• 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.

SizeM30

Class6.8

Diameter30 mm

Pitch (coarse)3.5 mm

Tensile600 MPa

Yield480 MPa

Proof440 MPa