M33 Grade 10.9 Torque Specification

Torque Values by Surface Condition

Stress area: 693.55 mm² · Proof load: 575,646 N · Clamp load (75%): 431,735 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	2849.5	2101.7	25220.2	29056.9
Oiled	0.15	2137.1	1576.2	18914.9	21792.4
Zinc Plated	0.18	2564.5	1891.5	22697.7	26150.7
Waxed	0.1	1424.7	1050.8	12609.7	14528.0
MoS₂	0.12	1709.7	1261.0	15132.1	17434.2
Galvanized	0.25	3561.8	2627.0	31524.6	36320.4

Stress area: 760.85 mm² · Proof load: 631,506 N · Clamp load (75%): 473,629 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	3126.0	2305.6	27667.4	31876.4
Oiled	0.15	2344.5	1729.2	20750.6	23907.3
Zinc Plated	0.18	2813.4	2075.1	24900.7	28688.8
Waxed	0.1	1563.0	1152.8	13833.7	15938.2
MoS₂	0.12	1875.6	1383.4	16600.5	19125.9
Galvanized	0.25	3907.4	2881.9	34583.4	39844.5

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 830 MPa × 693.55 mm² = 431,735 N

Step 2 — Torque (dry): T = 0.20 × 0.0330 m × 431,735 N = 2849.5 N·m

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

Structural steel (equivalent to ASTM A490), heavy machinery, high-strength critical joints, pressure vessels

• 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

Class10.9

Diameter33 mm

Pitch (coarse)3.5 mm

Tensile1040 MPa

Yield940 MPa

Proof830 MPa