M20 Grade 4.6 Torque Specification

Torque Values by Surface Condition

Stress area: 244.79 mm² · Proof load: 55,078 N · Clamp load (75%): 41,308 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	165.2	121.8	1462.1	1684.6
Oiled	0.15	123.9	91.4	1096.6	1263.4
Zinc Plated	0.18	148.7	109.7	1316.1	1516.3
Waxed	0.1	82.6	60.9	731.1	842.3
MoS₂	0.12	99.1	73.1	877.1	1010.5
Galvanized	0.25	206.5	152.3	1827.7	2105.7

Stress area: 271.5 mm² · Proof load: 61,088 N · Clamp load (75%): 45,816 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	183.3	135.2	1622.3	1869.1
Oiled	0.15	137.4	101.3	1216.1	1401.1
Zinc Plated	0.18	164.9	121.6	1459.5	1681.5
Waxed	0.1	91.6	67.6	810.7	934.1
MoS₂	0.12	110.0	81.1	973.6	1121.7
Galvanized	0.25	229.1	169.0	2027.7	2336.2

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 225 MPa × 244.79 mm² = 41,308 N

Step 2 — Torque (dry): T = 0.20 × 0.0200 m × 41,308 N = 165.2 N·m

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

Non-critical assemblies, light-duty applications, general-purpose hardware where high strength is not required

• 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.

SizeM20

Class4.6

Diameter20 mm

Pitch (coarse)2.5 mm

Tensile400 MPa

Yield240 MPa

Proof225 MPa