Flat washers

A flat washer is a metal fastening element in the shape of a flat ring, designed to improve the quality of assembly of various products. It increases the contact area between the nut and the bearing surface, strengthening the structure. Most often two washers are used at once: under the nut and under the bolt head. The range of application is wide — mechanical engineering, construction and repair, instrument making, agriculture, the furniture industry and other sectors.

Main functions of a round flat washer:

• The load is distributed evenly over the area of the bearing surface. The washer serves as a layer between the head of the bolt or nut and the surface material. This is important in cases of sharp pressure fluctuations on the joint.
• When installing a stud with metric thread, greater force can be applied.
• Easier to install and remove. Metric fasteners are made from the same types of steel, so similar elements can be joined faster.
• Protection against unplanned loosening. An installed flat washer without a chamfer strengthens the clamping point.
• The washer protects the surface coating from scratches when screwing in fastening bolts.
• Ensures tight contact of various gaskets.
• A washer can be used to reduce the mounting hole if it is larger than the diameter of the bolt or stud.
• Roughness at the fastener connection point is covered by the washer, which evens out the surface for bearing elements.

Manufacturing standards

The production of flat washers is regulated by the German standard DIN 125, the corresponding domestic standard GOST 11371-78, and the international standards ISO 7089 and ISO 7090.

DIN 125

The German standard DIN 125 has product grade A. The washer has only an internal chamfer; Vickers hardness ranges from 300HV to 400HV.

Materials used for manufacturing can include stainless steel, titanium, copper, brass, polyamide.

Coating:

• Electro-galvanizing — deposition of zinc ions on the surface in an electrolytic solution;
• Hot-dip galvanizing — immersion of the cold product in molten zinc;
• Yellow chromating (yellow zinc plating) — coating of products with a yellowish film by immersion in a solution with chromates.

Galvanizing of metal products is relatively inexpensive compared to other methods and remains one of the effective ways to protect fasteners and parts. For example, a galvanized flat washer with a diameter of M6, M8, M10 and M12 is widely used in industry and everyday life.

The main dimensions of flat washer DIN 125A without a chamfer are shown in the table:

d		d1	d2	s
Flat washer DIN125	M2	2.2	5.0	0.3
	M2.5	2.7	6.0	0.5
	M3	3.2	7.0	0.5
	M4	4.3	9.0	0.8
	M5	5.3	10.0	1.0
	M6	6.4	12.0	1.6
	M8	8.4	16.0	1.6
	M10	10.5	20.0	2.0
	M12	13.0	24.0	2.5
	M14	15.0	28.0	2.5
	M16	17.0	30.0	3.0
	M18	19.0	34.0	3.0
	M20	21.0	37.0	3.0
	M22	23.0	39.0	3.0
	M24	25.0	44.0	4.0
	M27	28.0	50.0	4.0
	M30	31.0	56.0	4.0
	M33	34.0	60.0	5.0
	M36	37.0	66.0	5.0
	M39	40.0	72.0	6.0
	M42	43.0	78.0	7.0

GOST 11371-78

Flat washer GOST 11371-78 is produced in two versions, which differ by the presence or absence of a chamfer.

1. A washer without a chamfer has product grade designated A and C.
2. A washer with a chamfer has product grade A. The chamfer is made at an angle of 30–45 degrees.

The grades are defined as follows: A — increased precision grade, C — coarse precision grade. The tolerance of the inner diameter for grade C has a larger allowance.

Washers are manufactured by cold stamping from steel, including stainless steel, brass, bronze and other non-ferrous metals and alloys. Vickers hardness for washers of product grade A must be at least 140 HV.

GOST 11371-78 also contains requirements for acceptance:

• washers with obvious external defects and incorrect shape are not allowed; the coating must be even, without burrs or roughness;
• compliance with the standard for the main parameter of the flat washer — the inner diameter — is strictly checked;
• hardness control of the washer is carried out using various methods.

An analog does not mean full compliance: washers without a chamfer under GOST may differ from DIN in diameter and thickness.

Comparison table of standards for flat washers GOST 11371-78 and DIN 125

Parameter	DIN 125	GOST 11371-78
d - thread diameter of the fastener, mm	from M1 to M90	from M1 to M48
h - washer thickness, mm	from 0.3 to 12	from 0.3 to 8
d2 - outer diameter of the washer, mm	from 3 to 160	from 3.5 to 92
Product grade	A	A and C
Vickers hardness, HV	from 300 to 400	A ≥ 140 C ≥ 100

How to order and buy

In the website catalogue, you can find the items you need by filtering products by categories and parameters. An online calculator for the weight of fasteners and hardware is available for calculating your order independently.

Products can be selected in the catalogue, added to the cart and ordered. The “Send request” button opens a form where you need to provide a contact person and a way to reach them — a sales manager will get in touch to advise on product availability or to discuss manufacturing items based on a sketch or drawing.