M33 Grade 4.8 Torque Specification

Torque Values by Surface Condition

Stress area: 693.55 mm² · Proof load: 215,000 N · Clamp load (75%): 161,250 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1064.3	785.0	9419.9	10852.9
Oiled	0.15	798.2	588.7	7064.7	8139.4
Zinc Plated	0.18	957.8	706.4	8477.2	9766.9
Waxed	0.1	532.1	392.5	4709.5	5425.9
MoS₂	0.12	638.6	471.0	5652.1	6511.9
Galvanized	0.25	1330.3	981.2	11774.2	13565.3

Stress area: 760.85 mm² · Proof load: 235,864 N · Clamp load (75%): 176,898 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	1167.5	861.1	10333.3	11905.2
Oiled	0.15	875.6	645.8	7749.7	8928.7
Zinc Plated	0.18	1050.8	775.0	9300.4	10715.2
Waxed	0.1	583.8	430.6	5167.1	5953.1
MoS₂	0.12	700.5	516.7	6200.0	7143.1
Galvanized	0.25	1459.4	1076.4	12916.8	14881.8

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 310 MPa × 693.55 mm² = 161,250 N

Step 2 — Torque (dry): T = 0.20 × 0.0330 m × 161,250 N = 1064.3 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.

SizeM33

Class4.8

Diameter33 mm

Pitch (coarse)3.5 mm

Tensile420 MPa

Yield340 MPa

Proof310 MPa