Circlip Guide: Types, Sizes & Installation

A circlip is one of those fasteners that tradespeople handle dozens of times without ever stopping to think about what it actually is or how it works — until one flies across the workshop and disappears under the bench. This guide covers everything you need to know: the different types, how to read a size chart, which pliers to use, and how to install and remove them correctly the first time.

Types of Circlips — Quick Reference

Internal and external are the primary categories, but within those categories there are several distinct construction types. The type determines groove compatibility, installation method, and performance characteristics.

Type	Installation direction	Plier holes	Groove profile	Typical load
Standard external (DIN 471)	Axial	Yes	DIN 471 tapered shoulder	Medium–high
Standard internal (DIN 472)	Axial	Yes	DIN 472 tapered shoulder	Medium–high
E-clip	Radial (side-on)	No	Simple circumferential groove	Light–medium
Bowed circlip	Axial	Yes	DIN 471/472 (wider groove)	Medium (preload)
Wire circlip	Axial	No	Round-bottomed groove	Light–medium
Heavy-duty	Axial	Yes	Heavy-duty DIN variant	High

What Is a Circlip?

A circlip — also called a snap ring, retaining ring, or C-clip — is a semi-flexible, open-ended metal ring that snaps into a machined groove on a shaft or inside a bore. Once seated, it acts as a mechanical shoulder: it allows rotation but prevents axial movement, stopping components from sliding along the shaft or out of the housing.

The core mechanism is simple. The ring is manufactured slightly smaller (for external clips) or slightly larger (for internal clips) than the groove it sits in. To install it, you deform the ring elastically — opening it to pass over a shaft, or closing it to fit inside a bore — then release it into the groove. The ring springs back toward its natural diameter, gripping the groove walls. The groove geometry (depth, width, and shoulder profile) determines how much axial load the circlip can resist.

The name "circlip" is a portmanteau of "circle" and "clip," and has become the standard Australian and British term for this fastener family. The American equivalent term is "snap ring" or "retaining ring." You will also encounter the term "Jesus clip" — a workshop colloquialism that refers to the circlip's tendency to launch itself at high velocity when being removed with pliers, prompting the inevitable exclamation when it disappears. This is not merely humorous: a releasing circlip under spring tension can travel several metres and cause eye injury. Safety glasses are not optional.

Internal vs External Circlips

The single most important distinction in circlips is whether the clip is internal or external. Getting this wrong means you are looking at a component that physically cannot be installed.

External Circlips

An external circlip fits around a shaft, seating in a groove machined into the shaft's outer diameter. To install it, you expand (open) the clip using external circlip pliers, pass it over the shaft to the groove position, and release. The clip springs closed into the groove. The clip's outer surface sits proud of the shaft OD, creating a shoulder that retains whatever component is loaded onto the shaft — a bearing, gear, pulley, or collar.

External circlips are the type you encounter most often in shaft-and-hub assemblies. They stop components from migrating along a shaft toward an open end. On a wheel hub, for example, an external circlip retains the bearing in its axial position. On a conveyor roller shaft, external circlips hold the roller body in place between two flanges.

Internal Circlips

An internal circlip fits inside a bore or housing, seating in a groove machined into the bore's inner diameter. To install it, you compress (close) the clip using internal circlip pliers, guide it into the bore to the groove position, and release. The clip springs open into the groove. The clip's inner surface now sits proud of the bore ID, creating a shoulder that retains whatever component sits inside the bore — a bearing outer race, bushing, or pin.

Internal circlips are standard in bearing housings and gear housings. The bearing's outer race is pressed into the bore, and the internal circlip prevents it from being pushed axially through the housing under load.

How to Tell Which You Have

If you are looking at an existing assembly and need to identify the clip type: an external circlip is visible around the outside of a shaft, with the lugs (plier holes) pointing radially outward. An internal circlip is recessed inside a bore, visible when looking into the opening, with lugs pointing inward toward the bore centreline. If you are selecting from scratch, the rule is: shaft groove → external clip, bore groove → internal clip.

Types of Circlips

Internal and external are the primary categories, but within those categories there are several distinct construction types. The type determines groove compatibility, installation method, and performance characteristics.

Standard Stamped Circlip (DIN 471 / DIN 472)

The most common type. Stamped from flat spring steel strip, these have a tapered cross-section (thicker at the outer radius for external, thicker at the inner radius for internal) with two lugs and plier holes for installation and removal. The tapered section locks into the groove's angled shoulder under axial load — the harder the clip is pushed, the tighter it wedges into the groove. DIN 471 is the standard for external clips; DIN 472 for internal. When someone says "circlip" without qualification, this is what they mean.

E-Clip (E-Ring)

An E-clip is installed radially — from the side — rather than axially. The groove for an E-clip is a simple circumferential groove without the tapered shoulder of a DIN 471/472 groove. The clip has an E-shaped cross-section: a central spine with three prongs that grip the groove. You push it onto the shaft from the side until it snaps into the groove; no pliers required, though a flat-bladed screwdriver or punch is often used.

E-clips are used where axial installation is impossible — for example, on a pin that is captive in an assembly and cannot have components slid over the end. They are common in light to medium-duty applications: lawn equipment, conveyor systems, light industrial machinery. They are not rated for high axial loads — the three-point contact provides considerably less retention force than a full DIN-style circlip in a tapered groove.

Bowed (Dished) Circlip

A bowed circlip is stamped with a deliberate axial bow — when viewed from the side, the ring is slightly curved rather than flat. When installed, this bow is partially compressed, and the spring-back force applies a continuous axial preload to the retained component. This takes up end-float (axial play) in an assembly, preventing the component from rattling or fretting in its groove.

Bowed circlips are used in precision bearing applications, instrument mechanisms, and anywhere that controlled end-float or preload is required. The standard flat circlip allows the retained component to move axially within the groove clearance; the bowed circlip eliminates that play.

Wire Circlip

A wire circlip is bent from round-section wire rather than stamped from flat strip. The circular cross-section means it requires a different groove profile — specifically a round-bottomed or semicircular groove, not the flat-bottomed tapered groove of a DIN 471/472 clip.

This is a critical compatibility point. Wire circlips and stamped circlips are not interchangeable in the same groove. A stamped DIN circlip installed in a wire-groove, or a wire circlip installed in a DIN tapered groove, will not seat correctly and will fail under load. If you are replacing a wire circlip, verify the groove profile before ordering.

Wire circlips are used in piston pin (wrist pin) applications in two-stroke and four-stroke engines, where the small bore diameter and the need for a low-profile clip favour the wire construction.

Heavy-Duty / Reinforced Circlip

Heavy-duty circlips are manufactured to tighter tolerances from higher-grade spring steel, with increased section thickness for higher axial load capacity. They follow DIN 471/472 groove profiles but are not interchangeable with standard clips — groove dimensions for heavy-duty clips differ. Specify by load rating, not just nominal size.

Type	Installation direction	Plier holes	Groove profile	Typical load
Standard external (DIN 471)	Axial	Yes	DIN 471 tapered shoulder	Medium–high
Standard internal (DIN 472)	Axial	Yes	DIN 472 tapered shoulder	Medium–high
E-clip	Radial (side-on)	No	Simple circumferential groove	Light–medium
Bowed circlip	Axial	Yes	DIN 471/472 (wider groove)	Medium (preload)
Wire circlip	Axial	No	Round-bottomed groove	Light–medium
Heavy-duty	Axial	Yes	Heavy-duty DIN variant	High

Circlip Materials

The material determines the circlip's corrosion resistance, operating temperature range, and suitability for specific environments. Most industrial circlips are spring steel, but several alternatives exist for specialised applications.

Spring Steel (Carbon Steel)

The standard material for the vast majority of industrial and automotive circlips. Carbon steel is heat-treated and tempered to give the combination of high yield strength (to resist permanent deformation under load) and adequate ductility (to allow elastic deformation during installation without cracking). Hardness is typically 47–52 HRC.

Spring steel circlips are supplied either self-colour (plain steel, no surface treatment) or zinc-plated for basic atmospheric corrosion protection. Self-colour clips are suitable for enclosed, lubricated applications — inside gearboxes, sealed bearing housings, engine components. Zinc-plated clips are adequate for mild workshop environments. Neither is appropriate for wet, chemical, or outdoor exposure.

Stainless Steel (304 and 316)

Stainless circlips are specified for corrosive environments: food processing equipment, marine and coastal installations, wash-down areas, and outdoor plant. The trade-off is reduced spring hardness compared to carbon steel — stainless spring material is softer, which reduces the maximum axial load rating for a given size compared to the carbon steel equivalent.

Select 304 stainless for general atmospheric and mild corrosive environments. Specify 316 stainless for chloride-rich exposure — coastal salt spray, CIP cleaning with chlorinated solutions, marine immersion. Do not assume 304 is adequate for a coastal Queensland installation; the chloride content of coastal air is sufficient to cause pitting on 304 over time.

Phosphor Bronze

Phosphor bronze circlips are used in hazardous-area equipment and electrical applications. Bronze has low spark-generation risk on impact (non-ferrous), making it appropriate for use near flammable or explosive atmospheres. It also has good electrical conductivity and is used where galvanic compatibility with other copper-alloy components is required. Not a common stocked item — typically a special-order material.

Beryllium Copper

Very high conductivity and good spring properties. Used in precision electrical connectors and instrument assemblies. Not generally available in standard DIN circlip profiles — a specialist item for specific applications.

Standards — DIN 471 and DIN 472

The two standards you will encounter on most circlip packaging and engineering drawings in Australia are DIN 471 and DIN 472. Both are German Industrial Standards (Deutsche Industrie Norm) that have become the de facto international standard for metric stamped circlips.

DIN 471 specifies external circlips for shafts. The nominal size equals the shaft diameter in millimetres. A DIN 471 – 25 circlip is for a 25mm shaft. The standard specifies the circlip's free diameter, section thickness, section height, and the corresponding groove dimensions (groove diameter, groove width, and groove corner radius) that the shaft must be machined to.

DIN 472 specifies internal circlips for bores. The nominal size equals the bore diameter in millimetres. A DIN 472 – 52 circlip is for a 52mm bore. The standard specifies the same parameters as DIN 471 but for bore grooves.

The groove dimensions in these standards are not arbitrary — the tapered shoulder and groove depth are designed so that the clip's bevelled inner face engages the groove shoulder under axial load, increasing the effective retention force. If the groove is cut to incorrect dimensions, the clip will either fall out (groove too wide or too shallow) or not seat fully (groove too narrow or too deep).

Other standards you may encounter: JIS B 2804 (Japanese standard, dimensionally similar to DIN 471/472 for most sizes), BS 3673 (British standard, now largely superseded by DIN in practice). Imperial-size circlips are available for equipment manufactured to inch standards — these are specified by shaft/bore diameter in fractional inches and follow their own groove dimension tables.

Circlip Sizes — How to Measure and Order

The most common ordering error is measuring the wrong dimension. Here is the correct approach.

For External Circlips (DIN 471)

Measure the shaft diameter. The nominal circlip size equals the shaft diameter. Do not measure the groove — the groove dimensions are specified by the standard and derived from the shaft diameter. If the shaft is 20mm, you need a DIN 471 – 20 circlip.

If you are replacing an existing circlip and the shaft groove is already cut, you can verify the shaft diameter from the groove itself: the shaft nominal diameter equals the groove diameter plus twice the groove depth (approximately), but measuring the shaft directly away from the groove is simpler and more accurate.

For Internal Circlips (DIN 472)

Measure the bore diameter. The nominal circlip size equals the bore diameter. A 40mm bore takes a DIN 472 – 40 circlip. Do not measure the groove ID.

External Circlip Reference Table (DIN 471 — Selected Metric Sizes)

Shaft Ø (mm)	Groove Ø d2 (mm)	Groove Width b (mm)	Circlip Thickness s (mm)	Circlip Free Ø (approx mm)
8	7.4	0.9	0.8	7.1
10	9.3	1.1	1.0	9.0
12	11.0	1.1	1.0	10.5
15	14.1	1.1	1.0	13.8
17	16.2	1.1	1.0	15.7
20	18.5	1.3	1.2	18.1
25	23.2	1.3	1.2	22.9
30	27.9	1.5	1.5	27.6
35	32.2	1.7	1.5	31.5
40	37.0	1.7	1.75	36.5
45	42.0	1.7	1.75	41.5
50	47.0	2.0	2.0	46.0
55	51.5	2.0	2.0	50.5
60	56.5	2.0	2.0	55.5
70	65.5	2.5	2.5	64.0
80	74.5	2.5	2.5	74.0
100	93.5	3.0	3.0	93.0

Internal Circlip Reference Table (DIN 472 — Selected Metric Sizes)

Bore Ø (mm)	Groove Ø d2 (mm)	Groove Width b (mm)	Circlip Thickness s (mm)	Circlip Free Ø (approx mm)
10	10.8	1.0	0.8	11.2
12	13.0	1.1	1.0	13.4
15	16.2	1.1	1.0	16.8
17	18.2	1.1	1.0	18.8
20	21.5	1.3	1.2	22.2
25	26.6	1.3	1.2	27.2
30	32.1	1.5	1.5	32.8
35	37.8	1.7	1.5	38.5
40	43.5	1.7	1.75	44.0
45	48.5	1.7	1.75	49.0
50	54.0	2.0	2.0	54.5
55	59.0	2.0	2.0	59.5
60	64.0	2.0	2.0	65.0
70	74.5	2.5	2.5	75.5
80	85.0	2.5	2.5	86.0
100	106.0	3.0	3.0	107.0

Dimensions are indicative for standard spring steel circlips. Always verify against the manufacturer's catalogue or DIN standard tables for critical applications.

Imperial Circlips

Imperial circlips are available for equipment manufactured to inch standards — older British-heritage machinery, American-specification plant, and some agricultural equipment. Imperial sizes are specified by shaft or bore diameter in fractional or decimal inches (e.g., ½", ¾", 1", 1¼"). The groove dimensions follow their own tables and are not interchangeable with metric grooves at nominally similar diameters. When ordering imperial circlips, specify both the nominal diameter and the standard (e.g., ½" external, AS circlip or DIN 471 equivalent in imperial).

Circlip Pliers — Types and Selection

"Circlip pliers" at 2,100 searches per month in Australia — more than "circlip" itself — tells you something: the pliers are frequently the blocker. Using the wrong plier type, or using pliers with tips that don't fit the clip, causes most of the installation problems, including the "Jesus clip" launch event.

The Four Basic Types

Internal straight: Tips point directly forward, parallel to the handles. When the handles are squeezed, the tips move together — compressing the clip. Used for internal circlips in bores where there is clear axial access. The straight configuration gives the best control for accessible bores and larger sizes.

Internal bent (angled tips): Tips are angled — typically at 45° or 90° — relative to the handles. The compress-on-squeeze action is the same as internal straight, but the angle allows access to bores that are recessed, at the bottom of a counterbore, or otherwise obstructed. If you find yourself twisting your wrist awkwardly with straight pliers, bent tips are the answer.

External straight: Tips point forward and the action is reversed — squeezing the handles moves the tips apart, expanding the clip. Used for external circlips on shafts with clear access. The most common type for general shaft work.

External bent (angled tips): Same expand-on-squeeze action, angled tips for restricted access. Used when the shaft groove is close to a housing face, deep in an assembly, or otherwise difficult to approach axially.

Combination and Reversible Pliers

Combination circlip pliers can be configured for either internal or external use by reversing the plier tips or switching between tip sets. These are useful for a general workshop where both internal and external clips are handled, and where the volume of circlip work does not justify a full set of dedicated pliers. The trade-off is slightly more setup time when switching between types and occasionally less ergonomic feel than a dedicated plier.

Knipex is the benchmark for quality circlip pliers in the Australian trade market — their 4-piece and 8-piece circlip plier sets cover the common size ranges and configurations. For a general maintenance fitter, a 4-piece set (internal straight, internal bent, external straight, external bent) in the 19–60mm range covers most everyday applications.

Tip Size and Fit

Circlip pliers come in different size ranges because the plier holes in the clip vary with clip size. The key rule: the tip must fit the plier hole fully. A tip that is too large cannot enter the hole. A tip that is too small enters but doesn't engage the hole wall — under spring tension, the tip slips out and the clip launches.

Most quality circlip pliers include interchangeable tips of different diameters to cover a range of clip sizes. When selecting a set, check that the stated size range covers the clips you are working with. Small engine circlips (8–12mm shaft) require finer tips than industrial bearing clips (40–100mm).

Plier type	Handle action	Tip action	Use case
Internal straight	Squeeze	Tips move together (compress)	Internal circlips, open access
Internal bent	Squeeze	Tips move together (compress)	Internal circlips, restricted/recessed bores
External straight	Squeeze	Tips move apart (expand)	External circlips, open access
External bent	Squeeze	Tips move apart (expand)	External circlips, restricted/deep shaft access
Combination / reversible	Squeeze	Configurable	General workshop, both clip types

How to Install a Circlip Correctly

Correct installation has three components: using the right pliers with fully-seated tips, installing the clip the right way around, and verifying the clip is fully seated in the groove. Missing any one of these causes failures that range from annoying (clip falls out during assembly) to hazardous (clip ejects under load in service).

Which Way Round Does a Circlip Go?

This is the question most articles skip, and it is the second-most-common installation error after wrong plier size. Stamped circlips have two distinct sides that result from the manufacturing process:

Smooth/chamfered side: The side from which the stamping die entered the metal. This side has a slight chamfer on the inner radius of the clip. This is the load-bearing side.

Burr/flat side: The underside of the stamp. This side has slight raised edges (burr) and a square inner edge. This side faces away from the retained component.

The smooth chamfered side must face the retained component — that is, the side that contacts the component being held against the clip. The reason matters: the groove in the shaft or bore has a matching tapered shoulder. When axial load is applied, the clip's chamfered face bears against the groove's tapered shoulder. The chamfer-to-taper contact geometry causes the clip to wedge tighter into the groove the harder it is pushed — self-reinforcing retention.

If the clip is installed reversed (flat/burr side toward the component), the flat edge bears against the rounded groove shoulder. Under axial load, the flat edge bites into the groove wall, the clip deforms, and it can ride up the chamfer and eject from the groove. This failure mechanism is responsible for a significant proportion of circlip field failures and is entirely preventable by installing the clip the right way around.

Installing an External Circlip (Step by Step)

1. Put on safety glasses. Position a cloth or your free hand to cover the clip during the final installation — this contains the clip if it slips from the pliers.
2. Select external circlip pliers of the correct size range for the clip. Check the tip diameter fits the plier holes fully — tips should enter without force and without visible play.
3. Hold the clip with the smooth (chamfered) face toward you. The smooth face will face the retained component, which is between the clip and the shaft shoulder.
4. Seat both plier tips fully into the plier holes. Both tips must be fully engaged before you apply any opening force.
5. Squeeze the handles to expand the clip. Expand only as far as needed to pass over the shaft — over-expansion permanently deforms the clip and reduces retention force.
6. With the clip expanded, slide it along the shaft to the groove position. Keep the clip square to the shaft axis — do not tilt.
7. Release the handles slowly, allowing the clip to spring closed into the groove.
8. Remove the pliers and check the clip is fully seated: run a fingernail or a flat probe around the entire circumference of the clip. The clip must sit flat and flush in the groove with no section standing proud. If any section is proud, the clip is not fully engaged — do not proceed. Partially seated circlips can eject under load with no warning.

Installing an Internal Circlip (Step by Step)

1. Safety glasses on.
2. Select internal circlip pliers of the correct size. Verify tip fit in the plier holes.
3. Orient the clip with the smooth (chamfered) face pointing toward the retained component (into the bore).
4. Seat both tips fully in the plier holes.
5. Squeeze to compress the clip until it is smaller than the bore diameter.
6. Guide the compressed clip into the bore, keeping it square to the bore axis. Do not tilt — a tilted clip can scratch the bore surface or spring into the bore in an uncontrolled manner.
7. Position the clip over the groove location and release the handles slowly. The clip will spring open into the groove.
8. Check seating — run a probe around the full inner circumference. The clip must sit flat in the groove, fully engaged around the entire perimeter.

Installing an E-Clip

E-clips do not require dedicated pliers. Hold the clip over the shaft groove (the shaft must be horizontal or supported). Position the central prong of the E over the groove. Press the clip onto the shaft with a flat-bladed screwdriver or a suitable punch, pushing firmly until the three prongs snap into the groove. Verify by trying to slide the clip axially — it should not move. Remove with a small flat screwdriver by levering one prong out of the groove.

How to Remove a Circlip

Removal is essentially installation in reverse, but with two additional considerations: the clip has been in service and may be corroded or deformed, and the clip should generally be replaced rather than reinstalled.

Standard Removal

Use the same plier type and tip-fit rules as for installation. For external circlips, expand the clip to clear the shaft diameter and slide it off. For internal circlips, compress the clip and withdraw it from the bore. Cover the clip as it releases — at the moment it clears the shaft or bore edge, the spring energy releases and the clip can launch.

Stuck or Corroded Circlips

A circlip that has been in a corrosive environment or has not been removed for years may be seized in the groove by rust or contamination. The approach:

1. Apply penetrating oil to the clip and groove. Allow a minimum of 10–15 minutes for penetration; longer for heavily corroded assemblies. Applying heat to the shaft or housing to expand the metal slightly, then allowing it to cool while the penetrating oil wicks in, significantly increases success rate on seized clips.
2. Re-attempt with circlip pliers, applying steady force rather than jerky leverage. Jerky force on a corroded clip is more likely to deform the plier holes and leave you with no purchase.
3. If the plier holes are damaged or obscured by corrosion, use two small flat-bladed screwdrivers — one at each ear of the clip — to pry it open (external) or closed (internal) simultaneously. This requires steadiness and eye protection.
4. As a last resort on an external circlip, a thin cold chisel driven carefully under the clip's outer edge can start it out of the groove. This damages the groove surface and should only be used when the clip will not be reinstalled and the groove condition does not matter.

Removal Without Pliers

This is the emergency method — not the recommended method. For external circlips: use two small flat-bladed screwdrivers, one at each ear, to lever the clip open until it clears the shaft. The risk is clip ejection (cover with a rag) and tip-hole damage that may prevent re-installation if the clip needs to be reused. For internal circlips: two fine screwdrivers levering toward the centre to compress the clip into the bore.

A pair of needle-nose pliers can substitute for internal circlip pliers in a genuine emergency — insert the tips into the plier holes and squeeze. The geometry is wrong (needle-nose tips are parallel, not angled inward like internal pliers) but it works for larger clips in accessible bores. It does not work well for small clips or restricted access.

Should You Reuse a Circlip After Removal?

The technically correct answer is: a circlip can be reused if it is undamaged and has not been permanently deformed. In practice, for most applications the correct answer is: replace it.

Here is the reasoning. Every time a circlip is expanded or compressed for installation or removal, it is deformed elastically. If the deformation stays below the yield point, the clip returns to its original geometry and retains its spring force. However, repeated cycles — or even a single cycle where the clip was over-expanded or over-compressed — can cause permanent deformation: the plier holes elongate, the ring develops a slightly enlarged diameter, or the section loses some springiness. A clip with even modest permanent deformation has reduced retention force compared to a new clip.

For non-critical applications (handle pivot pins, light covers, low-load assemblies), a circlip that passes visual inspection — no cracks, plier holes intact, ring sits flat without visible distortion — can reasonably be reused. For critical applications — engine piston pins, transmission shaft retention, bearing housing retention in load-bearing equipment — replace on every disassembly. The cost of a circlip is negligible. The cost of a retained component migrating because of a fatigued circlip is not.

Signs a circlip should be replaced:

• Visible cracks anywhere in the ring
• Plier holes deformed, elongated, or enlarged
• Ring does not sit flat (permanent bow in a non-bowed clip)
• Visible corrosion pitting, especially at the plier holes or inner radius
• Ring diameter visibly larger (external) or smaller (internal) than a new equivalent
• Any clip that had to be forced during removal — it has absorbed the force as deformation

Common Mistakes When Working With Circlips

These are the errors that account for the majority of circlip installation failures, field ejections, and injuries:

Wrong Plier Type

Using internal pliers on an external clip (or vice versa) results in the tip action working against you — you are trying to expand while the pliers compress, or vice versa. The clip fights you, you apply more force, and the clip launches when it eventually slips. Internal and external are not interchangeable. Check the plier type before you start.

Tips Not Fully Seated

Partially inserted tips — resting on the rim of the plier hole rather than fully through it — have a point contact with the clip rather than a face contact. Under spring force, the tip slides off the hole edge and the clip releases suddenly. Seat tips fully, every time. Feel them bottom out before applying opening or closing force.

Installed Backwards

As described in the installation section: smooth/chamfered face toward the retained component. A reversed circlip can appear to seat correctly and may hold initially. Under cyclic axial load, the ejection mechanism described above eventually triggers. If a circlip in a known-good groove is failing repeatedly, check orientation before assuming it is the wrong size.

Wrong Size

A clip that is one size too large fits loosely in the groove and can rattle out or be pushed out under low axial load. A clip that is one size too small cannot be fully seated in the groove. Both are dangerous. Measure the shaft or bore diameter — do not guess, and do not reuse packaging from a previous clip if you are not certain it was the right size to begin with.

Over-Expanding or Over-Compressing

Opening an external clip only as far as needed to clear the shaft, then releasing — not expanding it wide and slamming it down. Excessive deformation during installation is permanent. Clips that have been over-worked feel loose in the groove even when nominally the correct size. Use the minimum deformation necessary.

Mixing Metric and Imperial

A 20mm shaft and a ¾" shaft (19.05mm) are close enough in diameter that a clip from one system may appear to fit the other's groove — and it will, loosely. This is a groove mismatch, not just a size mismatch. The groove profile for a metric DIN 471 – 20 clip is not the same as the groove profile for a ¾" imperial clip, so the clip will not fully engage the groove shoulder even if it appears seated. Always confirm metric vs imperial before ordering.

Not Checking Seating After Installation

Visual inspection from above is not sufficient. Run a fingernail or a probe around the full circumference of the clip after installation. A clip that is fully seated sits flush in the groove with no section proud. A section that has jumped the groove edge looks seated from above but is sitting on the groove shoulder rather than in it — and it will eject as soon as any axial load is applied.

Common Applications

Circlips are found in nearly every mechanical assembly that involves rotating shafts, linear motion components, or pinned joints. These are the most common contexts an Australian maintenance fitter will encounter them:

Automotive and Vehicle

Piston pin (wrist pin) retention in petrol and diesel engines is one of the highest-volume circlip applications — wire circlips retain the piston pin from migrating axially through the piston bosses. Gearbox and transmission assemblies use circlips extensively: shaft retention, gear and synchroniser hub positioning, output shaft bearing retention. CV joints and axle shafts use circlips to retain the joint to the shaft. Wheel hub bearing retention — both inner bearing retention in the hub and outer retention in the knuckle — frequently uses external and internal circlips. Brake caliper pin retention and ABS sensor ring retention are further examples.

Industrial Bearings and Shafts

The largest category by part count in a typical industrial maintenance environment. External circlips retain bearings on shafts in conveyor rollers, pump shafts, gear reducers, agitators, and fan assemblies. Internal circlips retain bearing outer races in housings — the bearing is pressed into the housing bore and the circlip prevents it from being pushed axially through under load. Shaft collars and sprocket hubs are frequently retained by external circlips rather than set screws in lower-load applications.

Hydraulic and Pneumatic Cylinders

Piston rod retention within the cylinder barrel, and end-cap retention in some cylinder designs, uses internal circlips. These are safety-critical: the circlip is the sole mechanism preventing the piston rod assembly from being expelled from the cylinder under hydraulic pressure. Specification, groove condition, and clip condition must be to manufacturer's requirements.

Tools and Equipment

Angle grinder guard retention, drill chuck retention, impact driver anvil retention, and handle pivot assemblies in hand tools all use circlips. These are generally E-clips or standard external clips in smaller sizes (8–20mm range). A maintenance fitter disassembling a tool for a gear or bearing replacement will encounter these routinely.

Electric Motors

Bearing retention at both drive-end and non-drive-end of electric motors uses internal and external circlips in the end-shield bores and on the shaft respectively. When reconditioning motors, these clips should be replaced as a matter of course — the cost is trivial relative to the labour in the bearing replacement.

Agricultural and Mining Equipment

Pin and clevis joints in agricultural equipment (linkage pins on implements, PTO shaft joints, harvester components) use E-clips and external circlips for pin retention. Mining equipment — conveyor systems, screens, crushers — uses larger-format circlips in bearing housings and shaft retention. For high-vibration mining applications, circlip selection and groove condition are particularly important; vibration is the enemy of an incorrectly seated or undersized circlip.

Frequently Asked Questions

What is a circlip?

A circlip is a semi-flexible, open-ended metal ring that snaps into a machined groove on a shaft or inside a bore to prevent axial movement while allowing rotation. It creates a mechanical shoulder — a stop — that retains components in their axial position. Circlips are one of the most compact and cost-effective fastening methods for shaft and bore assemblies, requiring no threading, no adhesives, and no welding. They are removable and reusable (with limitations) and can be installed and removed with the correct pliers in seconds.

What is the difference between a circlip and a snap ring?

Nothing practical. They are the same fastener. "Circlip" is the Australian and British term; "snap ring" is the American term. "Retaining ring" is the broader generic category that includes circlips but also other ring-style retainers. "C-clip" is a colloquial alternative. In Australian industrial supply, you will typically find them catalogued as circlips. American machinery documentation will call them snap rings. If someone asks for a snap ring and gives you a shaft diameter, order a circlip of the same nominal size — they are dimensionally equivalent.

What is the difference between internal and external circlips?

An external circlip fits around a shaft, in a groove on the shaft's outer diameter. An internal circlip fits inside a bore, in a groove on the bore's inner diameter. They require different pliers — external pliers expand the clip to pass over the shaft; internal pliers compress the clip to fit inside the bore. They are not interchangeable: an external clip cannot function as an internal clip and vice versa, as the groove profiles, nominal size references, and retention geometry are all different.

What is an E-clip?

An E-clip (also called an E-ring or push-on clip) is installed radially from the side of the shaft rather than axially over the end. It has an E-shaped cross-section with a central spine and three prongs that grip a simple circumferential groove on the shaft. No pliers are required — the clip is pushed onto the shaft from the side until it snaps into the groove. E-clips are used where axial installation is impossible (the shaft is captive in an assembly with no access from the end) and in lighter-duty applications where the full retention force of a standard DIN circlip is not required.

Which way round does a circlip go?

The smooth (chamfered) side faces the retained component. Stamped circlips have a smooth chamfered side and a flat burred side as a result of the stamping process. The chamfered inner edge of the smooth side engages the angled shoulder of the groove under axial load, wedging the clip tighter the harder it is pushed. If installed reversed (flat side toward the component), the flat edge bears against the groove shoulder and can ride up under load, eventually ejecting the clip. If a circlip is failing in a correct groove, check orientation before assuming size is the problem.

How do you measure what size circlip you need?

For an external circlip (on a shaft): measure the shaft diameter. The nominal circlip size equals the shaft diameter in millimetres. For an internal circlip (in a bore): measure the bore diameter. The nominal size equals the bore diameter in millimetres. Do not measure the groove — the groove dimensions are derived from the shaft or bore diameter in the DIN 471/472 standard tables. If you are unsure of the shaft or bore size, measure it directly with a calliper rather than trying to measure the groove or the old clip.

Can you install a circlip without pliers?

In an emergency, yes — but it is not recommended. External circlips can be expanded over a shaft using two flat-bladed screwdrivers, one at each ear, levering outward simultaneously. The risks are high: the clip can launch from the screwdrivers, the plier holes can be damaged, and without control over the expansion the clip is easily over-deformed. Internal clips are harder to compress without dedicated pliers. If you regularly work with circlips, a basic four-piece plier set is a one-time investment that prevents the frustration, the risk, and the lost clips.

Why does my circlip keep coming out of its groove?

Four causes, in rough order of frequency: (1) Clip installed backwards — flat side toward the component; the ejection mechanism described above is triggered under axial load. (2) Clip not fully seated — one section has jumped the groove shoulder and appears seated but is resting on the groove face. (3) Wrong size — a clip one size too large sits loosely in the groove and can be displaced by vibration or low axial loads. (4) Groove damage or wear — a groove that has been burred, worn wide, or has an incorrect shoulder angle will not retain the clip correctly. Check orientation first, then seating, then size, then groove condition.

Can you reuse a circlip after removing it?

For non-critical applications, yes — if the clip passes inspection: no cracks, plier holes intact, ring sits flat, no permanent enlargement (external) or reduction (internal) of diameter. For critical applications — engine components, transmission shafts, load-bearing bearing retention, hydraulic cylinders — replace on every disassembly. A circlip costs cents; the consequences of a retained-component failure in a critical assembly are significantly more expensive and potentially unsafe.

What is the difference between DIN 471 and DIN 472?

DIN 471 specifies external circlips for shafts. DIN 472 specifies internal circlips for bores. Both are German Industrial Standards that define the clip geometry, material requirements, and the groove dimensions that the shaft or bore must be machined to. The nominal size in DIN 471 is the shaft diameter; in DIN 472, it is the bore diameter. A component marked "DIN 471 – 25" is an external circlip for a 25mm shaft. A component marked "DIN 472 – 52" is an internal circlip for a 52mm bore.

What material should I use for my circlip in a corrosive environment?

Stainless steel. For general corrosive environments and mild coastal exposure, 304 stainless is adequate. For chloride-rich environments — direct coastal exposure, marine installations, salt spray, or wash-down with chlorinated cleaning agents — specify 316 stainless. For food processing applications where both corrosion resistance and hygiene standards apply, 316 stainless is standard. Zinc-plated spring steel is suitable for enclosed, protected environments (inside a sealed gearbox or housing) but not for wet or outdoor exposure. Standard self-colour spring steel should not be used in any environment where moisture contact is expected.

What is the difference between circlip pliers and snap ring pliers?

Nothing — they are the same tool. "Circlip pliers" is the Australian and British term; "snap ring pliers" is the American term. In practice both refer to the same family of tools: internal straight, internal bent, external straight, external bent, and combination types. If you search for "snap ring pliers" in an Australian tool catalogue you will typically be redirected to or find the same products listed as circlip pliers. The selection criteria — internal vs external, straight vs bent, tip size range — are identical regardless of the name used.