A circlip (a portmanteau of circle and clip), also known as a C-Clip, Seeger ring, snap ring or Jesus clip,^[1] is a type of fastener or retaining ring consisting of a semi-flexible metal ring with open ends which can be snapped into place, into a machined groove on a dowel pin or other part to permit rotation but to prevent lateral movement. There are two basic types: internal and external, referring to whether they are fitted into a bore or over a shaft. Circlips are often used to secure pinned connections.

Details

When used to retain piston wrist pins /gudgeon pins the clips are known as wrist pin clips or wrist pin retainers or gudgeon pin clips . The most commonly used circlip for this application is a simple spring steel circlip , or plain wire ring.

Common examples include e-clips (e-ring) and the (both internal and external) snap ring or circlip . These general types of fasteners are sized to provide an interference fit onto (or into, in the case of an internal fastener) a groove or land when in use, such that they must be elastically deformed in order to install or remove them.

The term "Jesus clip" comes from the propensity of the clip's spring action to launch the clip at a high velocity when removing or installing. Typical remarks when the clip comes detached from the tool are "Oh Jesus, where did it go" or "Oh Jesus, we're gonna die."

Installation and lubrication

Since circlips are stamped out of sheet metal there is a smooth side and a rough side. To prevent potential damage, circlips are installed with the smooth side facing the part and the rough side facing out. Wet or dry lubrication is recommended to reduce friction against the circlip, maintaining its function.

Some circlips have two holes in the ends that are designed to be removed with specially shaped pliers tips. These are often referred to by their trade name; Tru-Arc clips or snap rings. They can be used as both external and internal retaining devices, hence, Tru-Arc pliers come in both compression (squeezing action) and expansion (spreading action) designs. Some Tru-Arc pliers are designed to be converted from one type to the other by simply moving the pliers screw in pivot point.

Circlips are designed to be removed with special circlip plier which can be reassembled for internal or external clips, but in field expedient situations, a pair of needle-nose pliers (for internal clips) or leverage with a flat-headed screwdriver (internal or external) is sometimes used.

Since most Tru-Arc snap rings are stamped from sheet steel, the stamping process results in a clip having a rounded side and a flat side, as the stamping die, acting like a cookie cutter slightly deforms and rounds the top of the clip’s edges as it penetrates the metal sheet.

The Tru-Arc snap ring must always be installed such that the rounded side of the ring is facing the side of the retaining groove that is holding the load or the force.

This is because no machined groove can or should be machined with perfectly square edges, as a perfect 90-degree square edge would constitute a stress riser and subject the shaft or part to cracking at that edge. Hence, snap ring grooves are always machined with their edges slightly (however microscopically) rounded.

Now, if one positions the snap ring with its flat side such that it is pushed into the rounded edge of the snap ring groove when load or force is applied, the flat and square edge of the snap ring will “bite” into the rounded edge of the retaining groove and as more force is applied the snap ring will distort as it rides up the rounded edge. This distortion will spread an external snap ring or compress an internal snap ring, leaving it prone to possibly being forced from the groove and releasing the part it is designed to hold.

• Definition with picture
• Historical background