M45 Grade 6.8 Torque Specification

Torque Values by Surface Condition

Stress area: 1306.09 mm² · Proof load: 574,680 N · Clamp load (75%): 431,010 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	3879.1	2861.1	34332.9	39556.0
Oiled	0.15	2909.3	2145.8	25749.5	29666.7
Zinc Plated	0.18	3491.2	2575.0	30899.7	35600.5
Waxed	0.1	1939.5	1430.5	17166.0	19777.5
MoS₂	0.12	2327.5	1716.7	20600.1	23734.0
Galvanized	0.25	4848.9	3576.4	42916.4	49445.2

Stress area: 1397.15 mm² · Proof load: 614,746 N · Clamp load (75%): 461,060 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	4149.5	3060.5	36726.2	42313.3
Oiled	0.15	3112.2	2295.4	27545.3	31735.7
Zinc Plated	0.18	3734.6	2754.5	33054.0	38082.5
Waxed	0.1	2074.8	1530.3	18363.5	21157.2
MoS₂	0.12	2489.7	1836.3	22035.7	25388.0
Galvanized	0.25	5186.9	3825.7	45908.0	52891.9

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 440 MPa × 1306.09 mm² = 431,010 N

Step 2 — Torque (dry): T = 0.20 × 0.0450 m × 431,010 N = 3879.1 N·m

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

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.

SizeM45

Class6.8

Diameter45 mm

Pitch (coarse)4.5 mm

Tensile600 MPa

Yield480 MPa

Proof440 MPa