M7 Washer Dimensions & Size

M7 washer dimensions are standardized for specialized mechanical and automotive applications, including engine component assembly, custom industrial mounting, and older European machinery maintenance. Specifically designed for fasteners with a 7 mm nominal diameter, these components ensure stable load distribution and protect mating surfaces from damage during tightening. This chart covers Form A plain washers, which feature a flat surface without a chamfer (unlike Form B).

The M7 size is available in two standardized series: the Normal Series (DIN 125A / ISO 7089) for standard load distribution and the Large Series (DIN 9021 / ISO 7093) for increased surface area. Based on these standards, M7 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 clamping force of high-tensile bolts.

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

Washer dimension diagram showing inner diameter, outside diameter, and thickness
M7 Standard Series Washer – DIN 125A/ISO 7089
Dimension Size (mm)
Min Max
Inner Diameter 7.4 7.62
Outside Diameter 13.57 14
Thickness 1.4 1.8
M7 Large Series Washer – DIN 9021/ISO 7093
Dimension Size (mm)
Min Max
Inner Diameter 7.4 7.62
Outside Diameter 21.48 22
Thickness 1.8 2.2
  • 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 “M7” designation mean on a washer?

The “M” stands for Metric, and the number represents the nominal thread diameter of the screw or bolt. An M7 washer is designed specifically for fasteners with a 7 mm nominal major diameter.

When should I use a Large Series (DIN 9021) M7 washer?

The Large Series (DIN 9021 / ISO 7093) features a significantly wider outside diameter—approximately three times the nominal thread size (22mm). It is used when fastening into soft materials like plastic or wood, or when a larger surface area is needed to bridge oversized holes and prevent the fastener head from pulling through.

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 M7 fasteners, a rating of 200 HV or 300 HV is standard for steel and stainless steel. This rating ensures the washer maintains its flatness and resists indentation when tightened to the torque levels required for secure mechanical fastening.

Is there a Small Series available for M7?

According to standard industrial datasets, a dedicated Small Series (DIN 433) is not typically utilized for the M7 size. If a compact profile is required, engineers often specify the Normal Series or look for custom specialized spacers.

In which materials are M7 washers commonly available?

M7 washers are most frequently produced in A2 (304) and A4 (316) Stainless Steel for corrosion resistance. They are also available in Zinc-Plated Steel for general mechanical use and Brass for specific decorative or conductive applications.