M52 Grade 4.8 Torque Specification

Torque Values by Surface Condition

Stress area: 1757.73 mm² · Proof load: 544,896 N · Clamp load (75%): 408,672 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	4250.2	3134.8	37617.5	43340.1
Oiled	0.15	3187.6	2351.1	28212.7	32504.6
Zinc Plated	0.18	3825.2	2821.3	33855.9	39006.3
Waxed	0.1	2125.1	1567.4	18808.7	21670.1
MoS₂	0.12	2550.1	1880.9	22570.3	26003.9
Galvanized	0.25	5312.7	3918.4	47021.4	54174.7

Stress area: 1828.6 mm² · Proof load: 566,866 N · Clamp load (75%): 425,150 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	4421.6	3261.2	39134.5	45087.9
Oiled	0.15	3316.2	2445.9	29350.9	33816.0
Zinc Plated	0.18	3979.4	2935.1	35220.7	40578.7
Waxed	0.1	2210.8	1630.6	19567.2	22544.0
MoS₂	0.12	2652.9	1956.7	23480.2	27052.2
Galvanized	0.25	5526.9	4076.4	48917.2	56358.9

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 310 MPa × 1757.73 mm² = 408,672 N

Step 2 — Torque (dry): T = 0.20 × 0.0520 m × 408,672 N = 4250.2 N·m

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

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.

SizeM52

Class4.8

Diameter52 mm

Pitch (coarse)5.0 mm

Tensile420 MPa

Yield340 MPa

Proof310 MPa