M8 Washer Dimensions & Size
The M8 size is one of the most widely used industrial standards and is available in three series: the Normal Series (DIN 125A / ISO 7089) for standard load distribution, the Large Series (DIN 9021 / ISO 7093) for significantly increased surface area, and the Small Series (DIN 433 / ISO 7092) for applications where radial space is limited. Based on these standards, M8 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 substantial clamping forces of grade 8.8 or 10.9 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.
| M8 Standard Series Washer – DIN 125A/ISO 7089 | ||
|---|---|---|
| Dimension | Size (mm) | |
| Min | Max | |
| Inner Diameter | 8.4 | 8.62 |
| Outside Diameter | 15.57 | 16 |
| Thickness | 1.4 | 1.8 |
| M8 Large Series Washer – DIN 9021/ISO 7093 | ||
|---|---|---|
| Dimension | Size (mm) | |
| Min | Max | |
| Inner Diameter | 8.4 | 8.62 |
| Outside Diameter | 23.48 | 24 |
| Thickness | 1.8 | 2.2 |
| M8 Small Series Washer – DIN 433/ISO 7092 | ||
|---|---|---|
| Dimension | Size (mm) | |
| Min | Max | |
| Inner Diameter | 8.4 | 8.62 |
| Outside Diameter | 14.57 | 15 |
| Thickness | 1.4 | 1.8 |
- 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 “M8” designation mean on a washer?
The “M” stands for Metric, and the number represents the nominal thread diameter of the screw or bolt. An M8 washer is designed specifically for fasteners with an 8 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.
When should I use a Large Series (DIN 9021) M8 washer?
The Large Series (DIN 9021 / ISO 7093) features an outside diameter of 24 mm, which is exactly three times the nominal thread size. It is indispensable when fastening into soft materials like wood, fiberglass, or thin sheet metal, where the clamping force must be spread over a maximum area to prevent the bolt head from crushing or pulling through the surface.
What does the HV rating mean on a washer?
HV stands for Vickers Hardness. For M8 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 high torque levels required for 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 15 mm compared to the Normal Series 16 mm. It is specifically intended for use with Socket Head Cap Screws or in recessed counterbores where a standard-width washer would interfere with the surrounding housing.
In which materials are M8 washers commonly available?
M8 washers are most frequently produced in A2 (304) and A4 (316) Stainless Steel for superior corrosion resistance. They are also widely available in Zinc-Plated Steel, Hot-Dip Galvanized Steel for outdoor use, and Nylon for insulation and vibration damping.