M27 Grade 6.8 Torque Specification

Torque Values by Surface Condition

Stress area: 459.41 mm² · Proof load: 202,140 N · Clamp load (75%): 151,605 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	818.7	603.8	7246.1	8348.4
Oiled	0.15	614.0	452.9	5434.4	6261.1
Zinc Plated	0.18	736.8	543.4	6521.2	7513.3
Waxed	0.1	409.3	301.9	3622.6	4173.7
MoS₂	0.12	491.2	362.3	4347.5	5008.9
Galvanized	0.25	1023.3	754.7	9057.0	10434.8

Stress area: 496.18 mm² · Proof load: 218,319 N · Clamp load (75%): 163,739 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	884.2	652.2	7825.8	9016.4
Oiled	0.15	663.1	489.1	5868.9	6761.8
Zinc Plated	0.18	795.8	587.0	7043.4	8114.9
Waxed	0.1	442.1	326.1	3912.9	4508.2
MoS₂	0.12	530.5	391.3	4695.3	5409.6
Galvanized	0.25	1105.2	815.2	9781.8	11269.9

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 440 MPa × 459.41 mm² = 151,605 N

Step 2 — Torque (dry): T = 0.20 × 0.0270 m × 151,605 N = 818.7 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.

SizeM27

Class6.8

Diameter27 mm

Pitch (coarse)3.0 mm

Tensile600 MPa

Yield480 MPa

Proof440 MPa