M48 Grade 6.8 Torque Specification

Torque Values by Surface Condition

Stress area: 1473.19 mm² · Proof load: 648,204 N · Clamp load (75%): 486,153 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	4667.1	3442.3	41307.3	47591.4
Oiled	0.15	3500.3	2581.7	30980.3	35693.3
Zinc Plated	0.18	4200.4	3098.1	37176.7	42832.3
Waxed	0.1	2333.5	1721.1	20653.2	23795.2
MoS₂	0.12	2800.2	2065.3	24783.9	28554.2
Galvanized	0.25	5833.8	4302.8	51633.5	59488.4

Stress area: 1602.9 mm² · Proof load: 705,276 N · Clamp load (75%): 528,957 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	5078.0	3745.3	44944.1	51781.4
Oiled	0.15	3808.5	2809.0	33708.1	38836.0
Zinc Plated	0.18	4570.2	3370.8	40449.7	46603.2
Waxed	0.1	2539.0	1872.7	22472.1	25890.7
MoS₂	0.12	3046.8	2247.2	26966.5	31068.8
Galvanized	0.25	6347.5	4681.7	56180.1	64726.7

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 440 MPa × 1473.19 mm² = 486,153 N

Step 2 — Torque (dry): T = 0.20 × 0.0480 m × 486,153 N = 4667.1 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.

SizeM48

Class6.8

Diameter48 mm

Pitch (coarse)5.0 mm

Tensile600 MPa

Yield480 MPa

Proof440 MPa