M33 Nut Dimensions: Hex & Thin Series

Q: What size wrench or spanner do I need for an M33 nut?

An M33 hex nut typically requires a 50 mm wrench or socket. The standard width across flats (s) for an M33 nut is 50.00 mm. Given the high torque required for M33 fasteners, hydraulic torque wrenches or specialized heavy-duty impact equipment are standard for industrial installation.

Q: What is a jam nut?

A jam nut is a low-profile hex nut, typically from the Thin Series (DIN 439), that is used to lock a standard nut in place. By tightening a standard nut against a jam nut, you create internal tension between the threads of both nuts and the bolt. This “jams” the assembly together, providing a mechanical lock that prevents loosening caused by vibration or rotation.

Q: Can a Thin Series nut handle the same torque as a Regular nut?

No. Because the Thin Series has fewer threads in contact with the bolt, it has a lower proof load. For M33 fasteners used in critical structural or machinery joints, using a thin nut as the primary fastener is dangerous as the threads are likely to strip or shear. Always use a Regular Series nut for primary load-bearing tasks.

M33 nut dimensions or sizes are critical for large-scale structural steel joints, marine engine assembly, and heavy industrial piping. This size is specifically engineered to mate with fasteners having a 33.00 mm nominal diameter and is available in M33 x 3.5 for the coarse series and M33 x 2.0 for the fine series.

This charts covers both the Regular Series (DIN 934 / ISO 4032) for standard load-bearing applications and the Thin or Half Series (DIN 439 / ISO 4035), which is ideal for jam nut or lock nut configurations or applications with limited vertical clearance. The thread dimensions comply with DIN 13-1 (coarse), DIN 13-21 (fine series), and ISO 68-1 standards to ensure a precise fit and reliable engagement across heavy-duty metric fastening systems.

Disclaimer: Actual dimensions, including the width across flats (spanner or wrench size), nut height, and thread tolerance may vary depending on the specific manufacturing class and material — always verify with the official product datasheet before use or buying.

Nut internal thread diagram depicting major diameter, minor diameter, and pitch diameter

Nut body diagram depicting width across flats, width across corners, diameter, and thickness or height

M33 x 3.5 Hex Nut – DIN 13-1/ISO 68-1
Dimension	Size (mm)
Dimension	Min	Max
Major Diameter	33	33.785
Pitch Diameter	30.727	31.007
Minor Diameter	29.211	29.771
Thread Pitch	3.5

M33 x 2.0 Hex Nut – DIN 13-21/ISO 68-1
Dimension	Size (mm)
Dimension	Min	Max
Major Diameter	33	33.513
Pitch Diameter	31.701	31.925
Minor Diameter	30.835	31.21
Thread Pitch	2.0

M33 x 1.5 Hex Nut – DIN 13-21/ISO 68-1
Dimension	Size (mm)
Dimension	Min	Max
Major Diameter	33	33.417
Pitch Diameter	32.026	32.226
Minor Diameter	31.376	31.676
Thread Pitch	1.5

M33 Hex Nut – DIN 934/ISO 4032 & ISO 8673
Diameter	33	35.6
Width Across Flats	49	50
Width Across Corners	55.37	Not specified
Height / Thickness	27.4	28.7

M33 Thin / Half Nut – DIN 439/ISO 4035 & ISO 8675
Diameter	33	35.6
Width Across Flats	49	50
Width Across Corners	55.37	Not specified
Height / Thickness	15.4	16.5

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Frequently Asked Questions

What size wrench or spanner do I need for an M33 nut?

An M33 hex nut typically requires a 50 mm wrench or socket. The standard width across flats (s) for an M33 nut is 50.00 mm. Given the high torque required for M33 fasteners, hydraulic torque wrenches or specialized heavy-duty impact equipment are standard for industrial installation.

What is a jam nut?

A jam nut is a low-profile hex nut, typically from the Thin Series (DIN 439), that is used to lock a standard nut in place. By tightening a standard nut against a jam nut, you create internal tension between the threads of both nuts and the bolt. This “jams” the assembly together, providing a mechanical lock that prevents loosening caused by vibration or rotation.

Can a Thin Series nut handle the same torque as a Regular nut?

No. Because the Thin Series has fewer threads in contact with the bolt, it has a lower proof load. For M33 fasteners used in critical structural or machinery joints, using a thin nut as the primary fastener is dangerous as the threads are likely to strip or shear. Always use a Regular Series nut for primary load-bearing tasks.