M1 Washer Dimensions & Size

Q: What does the “M1” designation mean on a washer?

The “M” stands for Metric, and the number represents the nominal thread diameter of the screw or bolt the washer is intended to fit. For example, an M1 washer is designed specifically for fasteners with a 1 mm nominal major diameter.

Q: What does the HV rating mean on a washer?

HV stands for Vickers Hardness. It is a measurement of the material’s resistance to indentation and deformation. For miniature sizes like M1, a high rating (such as 200 HV or 300 HV) is crucial to ensure the washer does not “cup” or collapse when the bolt is tightened to its required torque.

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

The primary difference lies in the edge finish. Form A washers are standard flat washers with a square edge and no chamfer. Form B washers feature a 30° to 40° chamfer (a beveled or sloped edge) on one outer side, according to DIN 125B and ISO 7090 standards. While Form A is common for general use, the chamfered edge of Form B is often preferred in high-finish engineering to prevent the washer edge from catching and to provide a more aesthetic, professional appearance.

M1 washer dimensions are standardized for high-precision applications, including miniature electronics, precision instruments, and micro-mechanical assemblies. Specifically designed for fasteners with a 1 mm nominal diameter, these components ensure stable load distribution and protect mating surfaces from damage during tightening. This chart is based on Form A plain or flat washers, which do not have a chamfer (unlike Form B). Since M1 is considered a miniature or micro size, this chart follows the DIN 433 / ISO 7092 standards for small series washers. Based on these standards, M1 washers typically feature a hardness of 200 HV or 300 HV (Vickers Hardness), providing the necessary structural integrity to prevent 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

M1 Small Series Washer – DIN 433/ISO 7092
Dimension	Size (mm)
Dimension	Min	Max
Inner Diameter	1.1	1.24
Outside Diameter	2.25	2.5
Thickness	0.25	0.35

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 “M1” designation mean on a washer?

The “M” stands for Metric, and the number represents the nominal thread diameter of the screw or bolt the washer is intended to fit. For example, an M1 washer is designed specifically for fasteners with a 1 mm nominal major diameter.

What does the HV rating mean on a washer?

HV stands for Vickers Hardness. It is a measurement of the material’s resistance to indentation and deformation. For miniature sizes like M1, a high rating (such as 200 HV or 300 HV) is crucial to ensure the washer does not “cup” or collapse when the bolt is tightened to its required torque.

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

The primary difference lies in the edge finish. Form A washers are standard flat washers with a square edge and no chamfer. Form B washers feature a 30° to 40° chamfer (a beveled or sloped edge) on one outer side, according to DIN 125B and ISO 7090 standards. While Form A is common for general use, the chamfered edge of Form B is often preferred in high-finish engineering to prevent the washer edge from catching and to provide a more aesthetic, professional appearance.

How many different forms are available for metric washers?

In standard metric specifications (like DIN 125), there are primarily two forms: Form A (no chamfer) and Form B (with chamfer). However, washers are also categorized by “series” based on their outside diameter: Small Series (DIN 433), Normal Series (DIN 125), and Large Series (DIN 9021).

In which materials are these washers commonly available?

Metric washers in this size range are most frequently produced in A2 (304) or A4 (316) Stainless Steel for excellent corrosion resistance. For specialized applications, they are also available in Zinc-Plated Steel, Brass, and Nylon for electrical insulation or weight reduction.