M18 Grade 4.8 Torque Specification

Torque Values by Surface Condition

Stress area: 192.47 mm² · Proof load: 59,666 N · Clamp load (75%): 44,749 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	161.1	118.8	1425.9	1642.8
Oiled	0.15	120.8	89.1	1069.2	1231.8
Zinc Plated	0.18	145.0	106.9	1283.4	1478.6
Waxed	0.1	80.5	59.4	712.5	820.9
MoS₂	0.12	96.7	71.3	855.9	986.1
Galvanized	0.25	201.4	148.5	1782.5	2053.7

Stress area: 216.23 mm² · Proof load: 67,031 N · Clamp load (75%): 50,273 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	181.0	133.5	1602.0	1845.7
Oiled	0.15	135.7	100.1	1201.0	1383.8
Zinc Plated	0.18	162.9	120.1	1441.8	1661.1
Waxed	0.1	90.5	66.7	801.0	922.8
MoS₂	0.12	108.6	80.1	961.2	1107.4
Galvanized	0.25	226.2	166.8	2002.0	2306.6

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 310 MPa × 192.47 mm² = 44,749 N

Step 2 — Torque (dry): T = 0.20 × 0.0180 m × 44,749 N = 161.1 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.

SizeM18

Class4.8

Diameter18 mm

Pitch (coarse)2.5 mm

Tensile420 MPa

Yield340 MPa

Proof310 MPa