M39 Washer Dimensions & Size

M39 washer dimensions are standardized for massive-scale structural and mechanical applications, including heavy bridge construction, power plant turbine foundations, offshore platform assembly, and large-scale industrial presses. Specifically designed for fasteners with a 39 mm nominal diameter, these components ensure stable load distribution and protect mating surfaces from damage during the extreme-torque tightening required for heavy industrial joints. This chart covers Form A plain washers, which feature a flat surface without a chamfer (unlike Form B).

M39 size is usually specified by the Normal Series (DIN 125A / ISO 7089), which is the industry standard for general heavy engineering and structural applications. Based on these standards, M39 washers typically feature a hardness of 200 HV or 300 HV (Vickers Hardness), providing the structural integrity required to prevent deformation or “cupping” under the massive clamping forces of high-tensile structural bolts.

Note: While these values reflect standard manufacturer datasheets, actual dimensions and tolerances may vary based on material (e.g., Stainless Steel vs. Hot-Dip Galvanized Steel) and manufacturing class. Always verify with the official product datasheet for critical applications.

Washer dimension diagram showing inner diameter, outside diameter, and thickness
M39 Standard Series Washer – DIN 125A/ISO 7089
Dimension Size (mm)
Min Max
Inner Diameter 40 40.62
Outside Diameter 70.8 72
Thickness 5.4 6.6
  • Inner Diameter – The diameter of the hole, designed to clear the bolt/screw thread.
  • Outside Diameter – The total width of the washer, determining the load distribution area.
  • Thickness – The height of the washer, providing the spacing and structural support.
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Frequently Asked Questions

What does the “M39” designation mean on a washer?

The “M” stands for Metric, and the number represents the nominal thread diameter of the screw or bolt. An M39 washer is designed specifically for fasteners with a 39 mm nominal major diameter.

What is the difference between Form A and Form B washers?

The difference lies in the outer edge finish. Form A washers have a square, flat edge and are the most common. Form B washers include a 30° to 40° chamfer (beveled edge) on one side, according to DIN 125B and ISO 7090 standards.

What standard is used for M39 washers?

M39 washers in this technical guide follow the Normal Series (DIN 125A / ISO 7089) standard. This is the industry benchmark for flat washers used with large hexagon bolts in structural and mechanical projects.

What does the HV rating mean on a washer?

HV stands for Vickers Hardness. For M39 fasteners, a rating of 200 HV or 300 HV is typical for steel and stainless steel. This ensures the washer resists the intense indentation forces generated during the high-torque installation of heavy-duty structural bolts.

In which materials are M39 washers commonly available?

M39 washers are most frequently produced in Hot-Dip Galvanized Steel for outdoor structural applications due to superior corrosion resistance. They are also available in A4 (316) Stainless Steel for marine environments and Plain (Black) Steel for heavy industrial machinery.