Cotter pins

A cotter pin is a fastening element made of steel wire with a semicircular cross-section. Finished products are manufactured in various design configurations. It is rarely used as a standalone fastener. Usually a cotter pin serves as a locking element in bolted connections. For this purpose, a special hole is made in the head or tip of the bolt, or on the face of the nut. The cotter pin is passed through this hole and the mounting channel in the secured part, and is secured at the exit by bending the legs apart in different directions. For ease of use, one end of the fastener is slightly longer than the other.

Range of cotter pins in the FLOK catalogue

Cotter pin fasteners are manufactured in several configurations and with various geometric parameters. The FLOK catalogue offers a wide selection of products that differ in length, source wire diameter, and fastener shape.

1. The straight (split) cotter pin meets the technical requirements of the German standard DIN 94, which corresponds to the domestic GOST 397-79 and the international ISO 1234. The product is formed by bending a wire segment of a specific size. After forming, a round eye remains at the bend point. This type of cotter pin is the most popular and in demand across various industrial and domestic fields.
2. The T-shaped cotter pin, like the previous fastener, is manufactured in accordance with DIN 94 and using the same principle. However, at the bend point a kind of crossbar is formed, giving the finished product a silhouette resembling the letter “T” referenced in its name.
3. The spring (wire) cotter pin to DIN 11024 (ISO 7072) has a complex configuration. One end of the product is a straight rod, while the other has a wavy shape. Depending on the eye design, products are divided into two types: with an incomplete loop or with a double twist resembling a spring coil. The loop makes it easier to install the cotter pin and remove it from the fastening assembly.
4. The ring cotter pin is manufactured to DIN 11023 (also known as an agricultural machinery linch pin). It has no equivalents among Russian or international standards. It is produced in two ways: 1) by twisting a wire segment into a ring with a special projection directed into the ring; 2) as a straight rod with a ring attached at one end.

How to determine cotter pin characteristics from the marking

The designation of each product encodes the cotter pin name, diameter and length, as well as the material grade, and the type and thickness of the protective coating. If there is no corrosion protection and the fastener is made of low-carbon steel, this is not reflected in the marking in any way. In addition, the designation of the standard according to which the specific product is manufactured must always be present.

For example, the marking 4×80.3.36. GOST397-79 belongs to a straight cotter pin with a diameter of 4 mm and a length of 80 mm. It is made of brass with a nickel coating 6 mm thick. The technical characteristics of the product comply with GOST 397-79.

Another marking example: 4×100 GOST 379-79. This cotter pin, with a diameter of 4 mm and a length of 100 mm, is made of low-carbon steel without corrosion protection. Its parameters meet the requirements of GOST 397-79.

The metals used to manufacture cotter pin fasteners also each have their own designation. Thus, 0 stands for low-carbon steels, 2 for corrosion-resistant steel alloys (austenitic chromium-nickel), 3 for brass, and 4 for aluminium alloys and pure aluminium.

Cotter pin manufacturing technology

Wire with a semicircular cross-section is used to manufacture this type of fastener. It is produced by drawing through wire-drawing machines or by flattening round wire on one side. Mass production is organized using automated equipment.

First, the raw material is fed into a straightening device consisting of several roller mechanisms arranged in a single plane. There are machines that operate simultaneously in two planes. They are equipped with two roller systems fixed perpendicular to each other.

After straightening, the wire is cut into segments of a specific length, pre-programmed in the equipment settings. The segments are then fed to the bending section, where they take on their final shape. During bending, the wire is positioned with its flat side facing inward.

Cotter pin fasteners: purpose and application

The main purposes of using cotter pins in bolted connections are: preventing the risk of nuts spontaneously unscrewing and providing convenient fixation of components under light loads. It is hard to find a field of human activity where these products are not used.

Installation of cotter pin fasteners is practiced in mechanical and instrument engineering, the food and medical industries, shipbuilding, weapons manufacturing, and precision technologies. They are used by manufacturers of automotive and agricultural machinery, as well as by DIY enthusiasts at home. No special tools are required for installation — a pair of pliers or combination pliers is enough.

FLOK supplies cotter pin fasteners in any quantity across the entire territory of the Russian Federation.