M56 Grade 5.8 Torque Specification

Torque Values by Surface Condition

Stress area: 2030.0 mm² · Proof load: 771,400 N · Clamp load (75%): 578,550 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	6479.8	4779.3	57351.1	66075.8
Oiled	0.15	4859.8	3584.4	43012.9	49556.4
Zinc Plated	0.18	5831.8	4301.3	51615.8	59468.0
Waxed	0.1	3239.9	2389.6	28675.5	33037.9
MoS₂	0.12	3887.9	2867.6	34410.8	39645.7
Galvanized	0.25	8099.7	5974.0	71688.4	82594.3

Stress area: 2120.0 mm² · Proof load: 805,600 N · Clamp load (75%): 604,200 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	6767.0	4991.1	59893.0	69004.5
Oiled	0.15	5075.3	3743.3	44920.2	51753.8
Zinc Plated	0.18	6090.3	4492.0	53903.7	62104.0
Waxed	0.1	3383.5	2495.5	29946.5	34502.2
MoS₂	0.12	4060.2	2994.6	35935.8	41402.7
Galvanized	0.25	8458.8	6238.9	74866.7	86256.1

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 380 MPa × 2030.0 mm² = 578,550 N

Step 2 — Torque (dry): T = 0.20 × 0.0560 m × 578,550 N = 6479.8 N·m

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

General industrial fastening, equipment mounting, moderate structural loads

• 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.

SizeM56

Class5.8

Diameter56 mm

Pitch (coarse)5.5 mm

Tensile520 MPa

Yield420 MPa

Proof380 MPa