M39 Nut Dimensions: Hex & Thin Series

Q: What size wrench or spanner do I need for an M39 nut?

An M39 hex nut typically requires a 60 mm wrench or socket. The standard width across flats (s) for an M39 nut is 60.00 mm. Given the extreme torque requirements for fasteners of this magnitude, hydraulic torque wrenches or industrial impact tools are almost always necessary for 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 M39 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.

M39 nut dimensions or sizes are critical for high-load anchor systems, heavy construction machinery, and power generation infrastructure. This size is specifically engineered to mate with fasteners having a 39.00 mm nominal diameter and is commonly available in M39 x 4.0 for the coarse 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) 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

M39 x 4.0 Hex Nut – DIN 13-1/ISO 68-1
Dimension	Size (mm)
Dimension	Min	Max
Major Diameter	39	39.877
Pitch Diameter	36.402	36.702
Minor Diameter	34.67	35.27
Thread Pitch	4.0

M39 x 3.0 Hex Nut – DIN 13-21/ISO 68-1
Dimension	Size (mm)
Dimension	Min	Max
Major Diameter	39	39.698
Pitch Diameter	37.051	37.316
Minor Diameter	35.752	36.252
Thread Pitch	3.0

M39 x 2.0 Hex Nut – DIN 13-21/ISO 68-1
Dimension	Size (mm)
Dimension	Min	Max
Major Diameter	39	39.513
Pitch Diameter	37.701	37.925
Minor Diameter	36.835	37.21
Thread Pitch	2.0

M39 x 1.5 Hex Nut – DIN 13-21/ISO 68-1
Dimension	Size (mm)
Dimension	Min	Max
Major Diameter	39	39.417
Pitch Diameter	38.026	38.226
Minor Diameter	37.376	37.676
Thread Pitch	1.5

M39 Hex Nut – DIN 934/ISO 4032 & ISO 8673
Diameter	39	42.1
Width Across Flats	58.8	60
Width Across Corners	66.44	Not specified
Height / Thickness	31.8	33.4

M39 Thin / Half Nut – DIN 439/ISO 4035 & ISO 8675
Diameter	39	42.1
Width Across Flats	58.8	60
Width Across Corners	66.44	Not specified
Height / Thickness	18.2	19.5

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Frequently Asked Questions

What size wrench or spanner do I need for an M39 nut?

An M39 hex nut typically requires a 60 mm wrench or socket. The standard width across flats (s) for an M39 nut is 60.00 mm. Given the extreme torque requirements for fasteners of this magnitude, hydraulic torque wrenches or industrial impact tools are almost always necessary for 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 M39 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.