M30 Washer Dimensions & Size

M30 washer dimensions are standardized for extreme-load structural and mechanical applications, including heavy bridge construction, industrial foundations, maritime infrastructure, and large-scale power generation equipment. Specifically designed for fasteners with a 30 mm nominal diameter, these components ensure stable load distribution and protect mating surfaces from damage during the high-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).

The M30 size is a primary heavy-industry standard available in three series: the Normal Series (DIN 125A / ISO 7089) for standard load distribution, the Large Series (DIN 9021 / ISO 7093) for a massive increase in surface area, and the Small Series (DIN 433 / ISO 7092) for tight radial clearances. Based on these standards, M30 washers typically feature a hardness of 200 HV or 300 HV (Vickers Hardness), providing the structural integrity required to prevent “cupping” or deformation under the massive clamping forces of grade 8.8, 10.9, or 12.9 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
M30 Standard Series Washer – DIN 125A/ISO 7089
Dimension Size (mm)
Min Max
Inner Diameter 31 31.39
Outside Diameter 55.26 56
Thickness 3.7 4.3
M30 Large Series Washer – DIN 9021/ISO 7093
Dimension Size (mm)
Min Max
Inner Diameter 33 34
Outside Diameter 89.8 92
Thickness 5 7
M30 Small Series Washer – DIN 433/ISO 7092
Dimension Size (mm)
Min Max
Inner Diameter 31 31.39
Outside Diameter 49.38 50
Thickness 3.7 4.3
  • 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 “M30” designation mean on a washer?

The “M” stands for Metric, and the number represents the nominal thread diameter of the screw or bolt. An M30 washer is designed specifically for fasteners with a 30 mm nominal major diameter.

When should I use a Large Series (DIN 9021) M30 washer?

The Large Series (DIN 9021 / ISO 7093) features a massive outside diameter of 92 mm, which is more than three times the nominal thread size. It is used when fastening into softer materials like structural timber or when bridging oversized holes in heavy base plates where the clamping force must be spread over a maximum area to ensure joint stability.

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 does the HV rating mean on a washer?

HV stands for Vickers Hardness. For M30 fasteners, a rating of 200 HV or 300 HV is standard for steel and stainless steel. This ensures the washer maintains its flatness and resists indentation even when subjected to the extreme torque levels required for large-scale structural mechanical joints.

What is the difference between Small Series (DIN 433) and Normal Series?

The Small Series (DIN 433 / ISO 7092) has a narrower outside diameter compared to the Normal Series. It is specifically intended for use with Socket Head Cap Screws or in recessed counterbores where a standard-width washer would be too large to fit the available housing.

In which materials are M30 washers commonly available?

M30 washers are most frequently produced in Hot-Dip Galvanized Steel for outdoor structural work due to its superior corrosion protection. They are also widely available in A4 (316) Stainless Steel for marine environments and Zinc-Plated Steel for general industrial hardware.