M56 Grade 4.8 Torque Specification

Torque Values by Surface Condition

Stress area: 2030.0 mm² · Proof load: 629,300 N · Clamp load (75%): 471,975 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	5286.1	3898.8	46785.9	53903.4
Oiled	0.15	3964.6	2924.1	35089.7	40427.8
Zinc Plated	0.18	4757.5	3509.0	42107.4	48513.2
Waxed	0.1	2643.1	1949.5	23393.4	26952.2
MoS₂	0.12	3171.7	2339.3	28071.9	32342.5
Galvanized	0.25	6607.7	4873.6	58483.1	67380.0

Stress area: 2120.0 mm² · Proof load: 657,200 N · Clamp load (75%): 492,900 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	5520.5	4071.7	48860.6	56293.6
Oiled	0.15	4140.4	3053.8	36645.6	42220.5
Zinc Plated	0.18	4968.4	3664.5	43974.1	50663.8
Waxed	0.1	2760.2	2035.8	24429.8	28146.3
MoS₂	0.12	3312.3	2443.0	29316.3	33776.2
Galvanized	0.25	6900.6	5089.6	61075.5	70366.8

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 310 MPa × 2030.0 mm² = 471,975 N

Step 2 — Torque (dry): T = 0.20 × 0.0560 m × 471,975 N = 5286.1 N·m

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

Light structural connections, furniture assembly, non-load-bearing joints

• 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

Class4.8

Diameter56 mm

Pitch (coarse)5.5 mm

Tensile420 MPa

Yield340 MPa

Proof310 MPa