Grooved Pins

What are grooved pins?

Grooved pins are press fit fasteners which lock themselves in place. They are frequently used as locking devices, bearing faces, pivots.and for locating elements that do not have a high degree of end load.

Grooved pins are solid, cylindrical pins with grooves in them. The most common grooved pins are formed from unhardened, low carbon steel that has been zinc plated. However many other materials can be used, including stainless steel and alloy steel. Heat treatments and finishes can be used to improve the shear resistance, so some grooved pins are plated with Zinc, Cadmium, Black Oxide, Oil or Nickel.

Grooves are cut into the pin at 120-degree intervals using three tools which penetrate slightly into the metal. As each grooving tool makes its groove the displaced metal forms a raised ridge on either side of the cut. This increases the diameter of the pin and is known as “Dx”. The normal diameter “D” is usually just a few thousandths of an inch smaller that the new “Dx”, but this depends on the original pin diameter, what material it is made of, and the style of groove that is being cut. No material is removed from the pin in this process, it is simply displaced.

grooved pin manufacturing

How do grooved pins work?

The grooved pin is inserted into a drilled hole that is very slightly larger than the pin’s original diameter. Groove pins can be inserted using a hammer, a hydraulic press or an air cylinder. When the pin is introduced into the hole the material that was displaced during the grooving process is forced back into the grooves, partially closing them and locking the pin in place. It is the compression of the expanded part of the pin which causes radial holding forces which keeps the pin secured within the drilled hole. This unique locking action is achieved with no permanent deformation of either the pin or the base material. Grooved pins have excellent holding power and will not move even when used in conditions where they are subject to vibrations or shocks.

What types of grooved pins are there?

The material, length and groove pattern depends on the situation in which the pin is used.

Some grooved pins have three parallel grooves which run the full length. They have short pilots and chamfers for easy insertion from either end. Pins with a parallel groove have a higher pullout strength than ones with a tapered groove due to the higher engagement between the hole walls and the pin. Grooved pins with full-length parallel grooves are commonly used to fit two or three units together with maximum rigidity

Grooved pins which are to be used as fastening or connecting elements frequently have three tapered grooves which run the full length. These can be used as cover retaining pins, pulley locking pins and flywheel balance plugs. Full-length taper grooves require less insertion force. Half-length taper grooves are used in assemblies where a free fit is required. 

Domed grooved pins have half-length grooves with a short pilot and these can be used for both through-hole and blind applications. For cord assemblies, the grooves are normally located in the centre of the pin and extend more than half the pin length. Pins with reverse taper grooves over half the length have an ungrooved section which acts as a handle or a stop. When the two ends need to act as pivots, as on hinges or clevises, centre grooves measuring a third of the length is the indicated.

What are the advantages of using Grooved pins?

Grooved pins are simple to use and fast and easy to install. They provide a permanent, functional, and reliable union between two or more pieces. There is no wrenching involved, the hole preparation is basic with no need to ream the drilled hole, and there are no exposed heads,

Grooved pins come in all different sizes and specifications for different jobs. When deciding which pin you need, consider the overall length, the diameter of the pin, the expansion diameter and the groove length. Pattern Fasteners Ltd. can manufacture any type of grooved pin to exactly meet your needs and they can assist you in determining what kind of grooved pin you require.