An 820 mm Spiral Retaining Ring: What Changes When a Ring Gets This Big

The ring in the photograph has an outside diameter of 820 mm. It is taller than the operator inspecting it, it is made from 304 stainless steel, and it is a spiral retaining ring — the same component that most engineers know at 20 mm, scaled up by a factor of forty. It is worth looking at closely, because almost nothing about making one scales linearly.

This article covers what actually changes at this diameter: why coiling rather than stamping is the only economic route, how the groove and the thrust load are calculated, why 304 was the right alloy for this part, and what handling a ring this size demands from a factory.

A note on names. The same component is catalogued as a retaining ring, a snap ring and, in British and Commonwealth usage, a circlip; ask what separates a retaining ring vs snap ring and the honest answer is regional habit rather than engineering. Coiled parts are listed as snap rings or as a spiral snap ring interchangeably. Retaining rings are then grouped by where they sit — an internal retaining ring locates in a bore, an external retaining ring locates on a shaft — and by how they are made: stamped from sheet, produced as a wire formed retaining ring, or coiled from flat wire, which is what a spiral ring is.

1. Why a ring this large has to be coiled

A stamped retaining ring is blanked out of sheet steel by a die. Scale that to 820 mm and two problems appear at once. The die becomes an enormous single-purpose tool that has to be paid for before the first part exists, and the blanking operation throws away everything inside the ring — at this diameter, well over ninety percent of the sheet. Neither problem has a good answer if the order quantity is fifty pieces.

A spiral wound retaining ring is made differently. Flat wire is fed on its narrow edge and coiled into two or more turns at the required diameter, then cut and finished. The machine sets the diameter, so a new size is a setup change rather than a new die, and the only material consumed is the wire that ends up in the part. That is why a large diameter retaining ring is normally a coiled retaining ring, and why a custom retaining ring at 820 mm costs far less than intuition suggests. At low volume the retaining ring cost is dominated by tooling, and a coiled part simply does not have any.

Coiling also changes the metal. The grain runs continuously around the circumference rather than being cut across by a blanking punch, so there is no severed grain at the load-bearing edge — one of the reasons a spiral ring holds its rated thrust load with a thinner section than a stamped equivalent.

2. What a spiral ring gives you that a stamped one does not

1. A uniform cross section retaining ring bears on the groove evenly. A stamped ring is thickest at the back and tapers toward its tips, so load distribution is never symmetrical.
2. A gapless retaining ring makes contact around the full circumference. Where a stamped ring leaves an open gap, a spiral ring closes on itself — a no gap retaining ring in the literal sense, and what a 360 degree contact retaining ring means in practice — no unsupported arc for a shaft end to push into.
3. A retaining ring without lugs has no protruding ears standing proud of the groove. Nothing sticks into the surrounding assembly, so the mating part can sit flush against the ring face.
4. A removable retaining ring can be supplied with a removal notch, so the ring is uncoiled out of its groove rather than levered out. On an 820 mm part, that is a genuine safety consideration, not a convenience.

The choice between a spiral retaining ring vs stamped retaining ring is therefore not only about cost at low volume. It is about whether the assembly needs even contact, a flush face and controlled removal — and at large diameters it usually does.

3. Structure: turns, duty and orientation

Three decisions define the part before any dimension is written.

1. Turns. A two turn spiral retaining ring is the standard build and covers most work; the photographed part is a 2 turn spiral retaining ring. A three turn spiral retaining ring, or a wider multi turn retaining ring, is specified where thrust load exceeds what two turns will carry within the available groove depth.
2. Duty. Light duty retaining ring, medium duty spiral retaining ring and heavy duty spiral retaining ring describe increasing radial wall and thickness for the same nominal diameter. Duty grade is chosen from the load, not from the diameter — a large ring in a lightly loaded housing cover does not need a heavy duty retaining ring.
3. Orientation. An internal spiral retaining ring — listed in some catalogues as a bore retaining ring or a housing retaining ring — is coiled slightly larger than the bore groove and springs outward into it; an external spiral retaining ring is coiled slightly smaller than the shaft groove and springs inward. Internal snap ring and external snap ring are the shop-floor names for the same two families.

Two further variants come up on drawings. A balanced spiral retaining ring is wound so the ring ends are positioned to cancel out-of-balance forces, which matters on rotating assemblies. A self locking retaining ring is designed to resist being pushed out of its groove under high axial load without needing a separate keeper. Alongside these, the constant section retaining ring is a related but distinct product — a single-turn ring of unchanging section, used where a shaft retaining ring must be very thin radially.

4. Why 304 for this part

The photographed ring is a 304 stainless steel retaining ring, and for a part of this size that is a deliberate choice rather than a default.

1. 304 forms well. Austenitic stainless work-hardens as it is coiled, so the ring gains strength during manufacture rather than needing a separate heat treatment at 820 mm — which would introduce distortion that is very hard to correct at this diameter.
2. It resists general corrosion. A stainless steel retaining ring is specified for humid, washdown, outdoor and lightly chemical environments where a carbon steel retaining ring would need plating that will eventually wear at the groove contact.
3. It is close to non-magnetic in the annealed condition, though cold working during coiling raises the permeability somewhat. Where a strictly non-magnetic part is required, that has to be stated on the drawing, not assumed.

The alternatives, briefly. A 302 stainless steel retaining ring offers higher spring strength where corrosion demand is lower; when a drawing says only stainless steel snap ring, this is the decision hiding behind it. A 316 stainless steel retaining ring is the corrosion resistant retaining ring for chloride and marine exposure. 65Mn retaining ring and spring steel retaining ring builds remain the cost-driven choice for dry, enclosed assemblies, and a carbon steel ring will always be stronger per millimetre of section than austenitic stainless. A beryllium copper retaining ring is used where conductivity or non-magnetic behaviour is mandatory, and a nickel alloy retaining ring is the high temperature retaining ring option when service runs above what stainless will hold. Fix the environment first; the retaining ring material list is short once you do.

5. Groove design and thrust load

A retaining ring assembly has two possible failure modes, and the weaker one governs. Either the ring shears out of its groove, or the groove itself deforms and lets the ring escape. Retaining ring thrust load therefore has to be checked twice — once against the ring section and once against the groove material — and the lower of the two numbers is the real retaining ring load capacity.

Retaining ring groove design at 820 mm follows the same rules as at 20 mm, with two amplified cautions. Retaining ring groove depth and retaining ring groove diameter must both be held to tolerance around the whole circumference, because an out-of-round groove on a large part will unload one arc of the ring and overload another. And the corner radius at the base of the groove matters more, because the stress concentration it creates is acting on a much longer contact length. Retaining ring groove dimensions should be taken from the ring drawing rather than from a generic table when the part is custom.

One more effect is specific to large diameters. A shaft or bore this size has meaningful thermal growth, so the working clearance between ring and groove at operating temperature is not the clearance measured at 20 °C. On stainless parts running hot, this is worth calculating rather than assuming.

6. Handling, installation and removal

Retaining ring installation is where a large ring stops resembling a small one, and how to install a spiral retaining ring at this diameter is a materially different procedure. A 20 mm ring is spiralled into its groove between finger and thumb. An 820 mm ring is a spring with real stored energy, and it takes two people and a defined method.

1. The ring is started at one point in the groove and wound in progressively, following the coil, not sprung in as a whole.
2. Retaining ring removal reverses the process, using the removal notch. Levering a large ring out of a groove risks both the groove edge and the operator.
3. Rings of this size ship on a supported former or as a controlled coil. Left unsupported in a crate, a large ring takes a permanent set that no amount of care at assembly will recover.

If you would like the procedure in writing before your parts arrive, ask for it with the quotation — for large diameter snap ring orders we supply an installation sheet with the shipment as standard.

7. Standards, and what to do beyond them

Most retaining ring standard references stop well short of 820 mm. In the metric world, GB 893 covers internal rings and GB 894 covers external rings; a DIN 471 retaining ring is the shaft series and a DIN 472 retaining ring the bore series, and both are widely used as the drawing reference in export work. An ANSI retaining ring follows the inch series instead. A metric retaining ring and an inch series retaining ring differ in more than units — the groove proportions differ too, so converting a dimension is not the same as converting a part.

Above the standard range, the standards stop being a catalogue and start being a method. Retaining ring dimensions, retaining ring sizes and every retaining ring size chart are derived rather than looked up: bore or shaft diameter, groove diameter, thrust load and material go in; radial wall, thickness and turn count come out. That is what a non standard retaining ring actually is — not an exotic part, just one whose numbers were calculated instead of read off a page. A custom spiral retaining ring is quoted from exactly those four inputs. If a listed size does fit, our retaining ring catalog and downloadable retaining ring catalogue remain the fastest route to a part number, with retaining ring CAD and a retaining ring 3D model available for the assembly check.

8. Where large rings like this one are used

An 820 mm ring is not a general-purpose item. A large spiral retaining ring — or an oversized retaining ring beyond any published series — appears where something large has to be located axially without a bolted flange.

1. Rotating equipment — a bearing retaining ring on a large bearing retaining ring seat, a slewing bearing retaining ring on excavators and tunnel boring machines, and a crane retaining ring in hoist drums.
2. Fluid power and process — a hydraulic cylinder retaining ring on large-bore cylinders, a pressure vessel retaining ring on closures, plus valve retaining ring and pump retaining ring work.
3. Energy and heavy industry — a wind turbine retaining ring in pitch and yaw assemblies, a turbine retaining ring in power generation, an oil and gas retaining ring and downhole retaining ring in well equipment, a mining equipment retaining ring and rolling mill retaining ring where shock loading is routine.
4. Corrosion-critical sectors — a marine retaining ring and food grade retaining ring, both of which drive the choice toward stainless in the first place.

Smaller diameters from the same production line serve gearbox retaining ring, automotive retaining ring, aerospace retaining ring and medical retaining ring applications — the process is identical, only the setup changes.

9. Making a ring this size, and proving it

Lispring has produced spiral retaining rings and wave springs since 2009 from a 21,400 m² plant in Wenzhou, China. Coiling large diameters is a capability, not a size class — the same imported Japanese equipment and German FERD design software that produce a 20 mm ring produce this one.

1. Roundness and free diameter are the controlling measurements at this size, and both are checked on the full part rather than sampled from an arc.
2. Material is verified by spectrometer on arrival, and the coiled part is checked in our CNAS-accredited ISO/IEC 17025 testing centre — hardness, metallographic structure after forming, and load testing where the drawing calls for it.
3. Quality systems: IATF 16949, AS9100D, ISO 13485, ISO 9001, ISO 14001, ISO 45001, ISO 50001, and ISO/IEC 27001 covering customer drawing confidentiality.
4. 43 authorized patents as of 2025 and roughly 7 % of annual revenue returned to R&D, across a deliberately narrow product family: spiral retaining rings, constant section rings, laminar seal rings and wave springs.
5. More than 10,000 standard items in stock and over 20,000 catalogued variants, with a US subsidiary shortening North American lead times.

Choosing a spiral retaining ring manufacturer for a part this size is not the same as choosing a retaining ring factory for catalogue items. Buyers evaluating a retaining ring manufacturer at this diameter ask two questions: can you actually coil it, and can you prove what you coiled. Photographs answer the first. The laboratory answers the second — which is why customers who arrive comparing several retaining ring manufacturers tend to consolidate onto one retaining ring supplier. If you are shortlisting retaining ring suppliers now, a sample with its full test report is the quickest comparison you can run.

10. Common questions

What is the largest spiral retaining ring you can make?

820 mm outside diameter — the ring shown is the largest we have produced to date. An 800mm retaining ring is comfortably inside that, and anything below it is routine. Beyond 820 mm the constraint is coiling setup, handling and packaging rather than the coiling process itself, so send the diameter and we will confirm directly rather than guess.

Does a large ring need new tooling?

No. Coiling sets diameter by machine setup, so an 820 mm ring needs no die. This is the single biggest cost difference against a stamped part at low volume, and it is why prototype quantities are practical.

304 or 316 for outdoor use?

304 is sufficient for general outdoor and washdown exposure. Move to 316 where chlorides are present — coastal air, de-icing salt, or process chemistry. If load matters more than corrosion, 302 or a carbon steel grade will carry more per millimetre of section.

How do I get a price?

Send the groove drawing, or the bore or shaft diameter, groove diameter, axial load and material. You will receive a recommended section, a turn count, a retaining ring price and a lead time. For a straightforward retaining ring quote we do not need a full assembly model — the groove is enough.

Request a quotation

Large diameter, small quantity, or a size no catalogue lists — those are the enquiries this line was built for. Contact: +86-577-62606161 · [email protected] · www.lispring.com