What is Mechanical Pins | Types Of Pins

Pins are used to fasten the shaft-supported elements to the shaft where they will prevent the axial movement, that might result from thrust load, and at the same time enable the transmission of torque. The simplest type of pins is the Straight pin which has a circular-cross section and it is specified by its diameter and length. Pins can be used in different ways to fix the shaft to the surrounding element.

The figure shows three different ways of using pins. In the first case the pin is used in a configuration similar to that of keys and in such case it is referred to as a round key. The most commonly used configuration for using pins is the radial configuration (the image in the middle).

In order to insert a pin, a hole of the same nominal diameter is drilled in the shaft and the surrounding element, then the pin is tightly inserted (usually under interference type of fit) through the two holes. However, it is not feasible to drill a radial hole through a gear or a pulley, therefore the gear or pulley needs to have a Hub into which the pin is inserted. Otherwise, an external hub or a collar may be used.

Pins are specified by their nominal diameter and length (d × L).

Pins are not only used for connecting shafts to the surrounding components, where they are used for other applications as well (such as positioning components accurately during assembly, making rotational joints between linkages, etc.).

Therefore many different types of pins are available, and these types include:

Tapered pins:

Tapered pins are typically used to fasten hubs or collars to shafts when the loads are small. According to ISO standards, the size of a tapered pin is specified by to the diameter at the small end and the length (the diameter of the large end is used to specify the pin size according to the American standard). Tapered pins have a fixed taper angle of 1% (i.e., about 0.57 degree).

types of pins - tapered , grooved , spring pin — types of pins – tapered , grooved , spring pin

Grooved pins:

Grooved pins are similar to straight pins but they have axial grooves (three groves) on their surfaces. The grooves could extend over the entire length of the pin or part of the length. The purpose of the grooves is to make it easier to compress the pin such that it can be installed tightly into smaller holes.

Spring pins:

Spring pins are hollow cylindrical pins with an axial cut along their length. The cut makes them more flexible and that enables them to be squeezed into smaller holes. They are usually used for making pin joints connecting linkages.

Dowel pins:

Dowel pins are cylindrical or conical in shape and they are usually used to keep two parts in a fixed position or to preserve the alignment during and after assembly. They are usually used where accurate alignment is essential. Dowel pins are sometimes made from wood or plastic according to the type of application in which they will be used.

Types of pins - clevis ,cotter ,hairpin cotter — Types of pins – clevis ,cotter ,hairpin cotter

Clevis pins:

Clevis pins are used in a clevis and they are usually held in place by cotter pins.

Cotter pins:

Cotter pins are used to keep parts in position. A cotter pin has a round head and ends that are bent after assembly to be locked in position. Cotter pins are typically used with slotted nuts to keep the nuts from being loosened. Another type of cotter pins is the Hairpin cotter which has a preformed shape and behaves like a locking spring to keep parts such clevis pins in position.