DIN 471, DIN 472 and DIN 6799 explained
Three standards cover almost every metric retaining ring you will meet. Picking the wrong one is usually a matter of measuring the wrong surface, not of choosing the wrong part.
What a retaining ring does
A retaining ring sits in a machined groove and forms a removable shoulder. That shoulder holds a bearing, gear, pulley, bush or pin in position against axial load — load along the axis of the shaft — without the cost of machining an integral collar or the permanence of a pressed fit.
Because the ring is a shoulder rather than a clamp, it resists movement along the shaft but does nothing to stop rotation. Anything that must not turn needs a key, spline, pin or interference fit as well.
DIN 471 — external circlips, fitted to a shaft
DIN 471 covers rings that fit into a groove machined around the outside of a shaft. The ring is expanded to pass over the shaft, then relaxes into the groove, and the portion standing proud of the shaft forms the shoulder.
The nominal size quoted against a DIN 471 ring is the shaft diameter, not any dimension of the ring itself. A 12 mm external circlip is the ring for a 12 mm shaft; its free outer diameter is larger than 12 mm and its inner diameter, once seated, is smaller. This is the single most common ordering mistake — measuring the old ring with callipers and ordering that number.
DIN 472 — internal circlips, fitted to a bore
DIN 472 covers rings that fit into a groove machined inside a housing or bore. The ring is compressed to pass into the bore, then springs outwards into the groove, and the portion standing proud of the bore wall forms the shoulder that retains a bearing or bush from within.
The nominal size quoted against a DIN 472 ring is the bore diameter. A 20 mm internal circlip is the ring for a 20 mm bore. External and internal rings are not interchangeable and work in opposite directions: one has to be expanded to fit, the other compressed.
DIN 6799 — E-clips, fitted from the side
DIN 6799 covers E-clips, also called E-rings or retaining washers. Rather than passing over the end of a shaft, an E-clip is pushed on radially — from the side — with its open jaws springing around the groove. That makes it the practical choice wherever the shaft end is captive, obstructed or simply too far away to reach.
The nominal size quoted against a DIN 6799 clip is the groove diameter, measured at the bottom of the groove rather than across the full shaft. A clip listed as 4 mm suits a 4 mm groove, which will have been cut into a larger shaft. E-clips are common on linkages, small spindles, control mechanisms and light assemblies.
Choosing between them
The choice is set by the assembly, not by preference. If the groove is on the outside of a shaft and you can reach the shaft end, you need DIN 471. If the groove is inside a bore, you need DIN 472. If the groove is on a shaft you cannot get to the end of, you need DIN 6799.
Where more than one will physically fit, the deciding factors are the load the shoulder has to carry and the access you have for pliers. E-clips carry less thrust than an equivalent DIN 471 ring because less of the clip bears on the groove wall, so they are not a like-for-like substitute on a loaded joint.
The names all mean the same thing
Circlip, snap ring, retaining ring, lock ring and Seeger ring are used more or less interchangeably in the trade. Circlip and Seeger both began as trade names and passed into general use. None of them tells you whether a part is internal or external, so a supplier will always come back and ask.
The useful description is the standard plus the nominal size plus the surface it is measured on — "DIN 471, 25 mm shaft" leaves nothing to interpret.
Common questions
What is the difference between DIN 471 and DIN 472?
DIN 471 rings are external: they fit into a groove on the outside of a shaft and must be expanded to go on. DIN 472 rings are internal: they fit into a groove inside a bore and must be compressed to go in. They are not interchangeable, and each is sized by the surface it fits — shaft diameter for DIN 471, bore diameter for DIN 472.
Is a circlip the same as a snap ring or a retaining ring?
Yes. Circlip, snap ring, retaining ring, lock ring and Seeger ring all describe the same class of part. None of the names indicates whether the ring is internal or external, so quote the standard and the nominal size as well.
Does a 12 mm circlip fit a 12 mm shaft?
For a DIN 471 external circlip, yes — the nominal size is the shaft diameter, so a 12 mm ring is the ring for a 12 mm shaft. The ring's own free outside diameter is larger than 12 mm, so measuring an old ring across its widest point will give you the wrong number to order against.
What does DIN stand for?
Deutsches Institut für Normung, the German standards institute. A DIN number identifies the published standard that governs the part's dimensions and tolerances, which is why quoting it removes ambiguity between suppliers.
Can circlips be reused?
Reuse is not recommended. Fitting and removal both flex the ring, and it is easy to take it past the point where it returns to its original free diameter. A ring that no longer sits fully down in the groove is the usual cause of a retained part working loose, and the cost of a replacement is trivial against the cost of the failure.
Other guides
How to measure for a circlip
The ring you pulled out is the least reliable thing to measure. Measure the feature it sits in, and the size falls out of the standard.
Fitting and removing circlips safely
Most circlip failures are fitting failures. A ring that was over-expanded on the way in will not hold, however right the part number was.
Circlip materials and finishes
Carbon spring steel does almost every job. The cases where it does not are predictable, and they are worth knowing before the assembly is closed up.
Need it identified?
Send the dimensions you were able to measure, along with the quantity you need. Imperial sizes, obsolete references and parts identified from a drawing or a sample are handled through the trade desk.
Send a trade enquiry