M52 Grade 5.8 Torque Specification

Torque Values by Surface Condition

Stress area: 1757.73 mm² · Proof load: 667,937 N · Clamp load (75%): 500,953 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	5209.9	3842.6	46111.5	53126.4
Oiled	0.15	3907.4	2881.9	34583.4	39844.5
Zinc Plated	0.18	4688.9	3458.4	41500.3	47813.7
Waxed	0.1	2605.0	1921.3	23056.2	26563.7
MoS₂	0.12	3125.9	2305.5	27666.6	31875.4
Galvanized	0.25	6512.4	4803.3	57639.6	66408.2

Stress area: 1828.6 mm² · Proof load: 694,868 N · Clamp load (75%): 521,151 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	5420.0	3997.6	47971.1	55268.8
Oiled	0.15	4065.0	2998.2	35978.3	41451.6
Zinc Plated	0.18	4878.0	3597.8	43174.0	49741.9
Waxed	0.1	2710.0	1998.8	23985.5	27634.4
MoS₂	0.12	3252.0	2398.6	28782.6	33161.3
Galvanized	0.25	6775.0	4997.0	59963.8	69086.0

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 380 MPa × 1757.73 mm² = 500,953 N

Step 2 — Torque (dry): T = 0.20 × 0.0520 m × 500,953 N = 5209.9 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.

SizeM52

Class5.8

Diameter52 mm

Pitch (coarse)5.0 mm

Tensile520 MPa

Yield420 MPa

Proof380 MPa