DIN 11024 Spring Hairpin Cotter Pin

A spring cotter pin is a resilient steel wire bent in half, with one end straightened and the other shaped into a wave.

A round eye is formed at the bend.

The spring hairpin cotter pin is manufactured according to the German standard DIN 11024, whose international counterpart is ISO 7072. The term “counterpart” does not mean full equivalence, so when selecting fasteners it is recommended to additionally check the parameters with specialists.

Types of spring hairpin cotter pins per DIN 11024

Different versions of spring-type cotter pin fasteners differ in the diameter of the source material (wire), steel grade, quality of corrosion protection, and product length. Two types of cotter pins are distinguished by their shape.

The spring hairpin cotter pin DIN 11024 Form D has a head made with a double wire coil. It is effective as a locking device that prevents loosening or self-unscrewing of bolted connections. The fastener is used in the machine-building and automotive industries, as well as in applications where fastener assemblies with low loads need to be reliably secured.

The eye of the spring hairpin cotter pin DIN 11024 Form E is shaped as an incomplete ring. In appearance, the product resembles a bobby pin used in women’s hairstyling. Like the previous version, the Form E cotter pin is used to secure lightly loaded parts, assemblies and components. Its use improves the strength of the bolted connection and helps prevent nuts from self-unscrewing, especially under dynamic and vibration loads.

What materials are used to make spring cotter pins

Various steel alloys are most commonly used to produce hairpin cotter pins. This can be plain steel, treated with zinc powder in electroplating equipment for corrosion protection. Such products can withstand humid operating conditions.

If the fastener assemblies being created will come into contact with a more demanding environment, cotter pins made of austenitic stainless steel grade A2 should be selected. Chromium-nickel steel with molybdenum added, grade A4, is used to manufacture fasteners intended for operation in contact with acids, alkalis, and seawater.

The source raw material is wire. To give its cross-section a half-round shape, round-section wire rod is passed through drawing equipment or flattened by another method.

Installation technique for the spring hairpin cotter pin

For correct use of D and E cotter pins, holes must be provided in advance in the head of the bolt and/or nut. When assembling the fastener joint, the straight leg of the cotter pin is inserted into the hole, and the wave-shaped part snaps into place on the outside at several points simultaneously, like a spring.

The DIN 11024 hairpin cotter pin is used across various branches of industrial production: in equipment assembly in mechanical engineering, in the outfitting of instruments, units and apparatus of various purposes. It is also used in automotive equipment, machine tool building, and for DIY repairs.

Selecting cotter pins by parameters

FLOK supplies spring hairpin cotter pins DIN 11024. Use the filter in the catalogue to select the right type by length, wire diameter, and material.

d₁	d₃	l
2.5	2.25	42
3.2	2.8	48
4.0	3.6	64
5.0	4.5	80
6.3	5.6	97
7.0	6.3	125
8.0	7	150