M42 Washer Dimensions & Size

M42 washer dimensions are standardized for high-capacity structural and mechanical engineering, including heavy-duty turbine mounting, bridge abutment anchoring, large-scale industrial presses, and maritime propulsion systems. Specifically designed for fasteners with a 42 mm nominal diameter, these heavy-duty components ensure uniform load distribution and protect critical mating surfaces from deformation during the extreme-torque tightening required for industrial-scale joints. This chart covers Form A plain washers, which feature a flat surface without a chamfer.

The M42 size is represented by the Normal Series (DIN 125A / ISO 7089), the primary standard for general heavy engineering and structural applications. These components typically feature a hardness of 200 HV or 300 HV (Vickers Hardness), providing the structural integrity required to prevent “cupping” or indentation under the massive clamping forces generated by high-tensile structural bolts.

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

Washer dimension diagram showing inner diameter, outside diameter, and thickness
M42 Standard Series Washer – DIN 125A/ISO 7089
Dimension Size (mm)
Min Max
Inner Diameter 43 43.62
Outside Diameter 76.8 78
Thickness 6 8
  • 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 “M42” designation mean on a washer?

The “M” stands for Metric, and the number represents the nominal thread diameter of the fastener. An M42 washer is engineered specifically for bolts and screws with a 42 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.

Which standard is used for M42 washers?

M42 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 signify for M42 hardware?

HV stands for Vickers Hardness. For M42 hardware, a rating of 200 HV or 300 HV is standard. This rating ensures the washer maintains its flatness and resists the intense indentation forces produced during the high-torque installation of large-diameter structural bolts.

Which materials are standard for M42 washers?

M42 washers are commonly manufactured in Hot-Dip Galvanized Steel for superior corrosion resistance in outdoor structural environments. They are also available in A4 (316) Stainless Steel for marine and chemical applications and Plain (Black) Steel for heavy internal machinery.