ENGINEERING REFERENCE
Retaining Ring & Snap Ring Size Chart
Complete retaining ring size chart covering ANSI B27.7 and DIN 471/472 standards. Groove dimensions, ring thickness, free diameter, and maximum RPM for 26 standard sizes from 3/8″ to 3″ — shaft (external) and bore (internal) applications.
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ANSI B27.7 / DIN 471/472
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Groove Dimensions & Tolerances
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Free Excel Download
Retaining Ring Reference
Seven critical dimensions per standard
Groove Dia.Shaft / Bore
Groove WidthThickness Fit
Ring ThicknessANSI B27.7
Max RPMSpeed Limit
Downloadable Spreadsheet
Retaining Ring & Snap Ring Size Chart
FASTENER FUNDAMENTALS
What Are Retaining Rings & Snap Rings?
A retaining ring — also called a snap ring or circlip — is a stamped metal ring that fits into a machined groove on a shaft or inside a bore to stop components from sliding axially out of position.
Retaining ring is the broad category: any mechanical fastener that seats into a groove to prevent axial movement. Snap ring (or circlip) is a specific type — a C-shaped ring with tapered cross-section and lug holes for plier installation. Every snap ring is a retaining ring, but spiral rings, E-clips, and constant-section rings are also retaining rings that are not snap rings.
Why the Groove Matters
The retaining ring itself is a commodity — stamped to tight tolerances. The part you control is the groove. If groove diameter is off, the ring won’t seat. If groove width is undersized, the ring binds. If depth is too shallow, thrust capacity drops.
External vs. Internal
External (shaft) rings fit into a groove around the outside of a shaft — the free inside diameter is smaller than the groove so the ring grips under tension. Internal (bore) rings fit inside a housing bore — the free outside diameter is larger, so the ring expands outward to seat.
Standards Covered
ANSI B27.7 / ASME B18.27 for inch-series. DIN 471 (shaft) and DIN 472 (bore) for metric. JIS B 2804 and ISO 464 also referenced. This page compiles all five standards into one reference.
ANSI B27.7 & DIN 471/472 DATA
Retaining Ring Size Chart — Shaft & Bore Dimensions
External (shaft) and internal (bore) retaining ring dimensions with groove diameter, groove width, ring thickness, free diameter, and maximum RPM for standard sizes.
Note: Dimensions are from ANSI B27.7 / ASME B18.27 (inch series) and DIN 471/472 (metric). Values shown are typical for carbon spring steel rings. Groove tolerances must be held to ±0.002″ for proper seating. Always verify against your ring supplier’s catalog for production applications.
External Retaining Rings — Shaft Sizes 3/8″ to 3″
External rings fit into a groove on the outside of a shaft. The ring’s free inside diameter is smaller than the groove, so it grips the shaft under tension. Max RPM values assume balanced loading with standard carbon spring steel.
| Shaft Dia. | Ring Thick. | Free Dia. | Groove Dia. | Groove Width | Groove Depth | Max RPM |
|---|---|---|---|---|---|---|
| 3/8″ | 0.025″ | 0.360″ | 0.348″ | 0.028″ | 0.021″ | 32,000 |
| 7/16″ | 0.025″ | 0.422″ | 0.409″ | 0.028″ | 0.021″ | 28,000 |
| 1/2″ | 0.035″ | 0.484″ | 0.468″ | 0.038″ | 0.023″ | 24,000 |
| 9/16″ | 0.035″ | 0.547″ | 0.530″ | 0.038″ | 0.023″ | 21,000 |
| 5/8″ | 0.042″ | 0.609″ | 0.590″ | 0.046″ | 0.027″ | 19,000 |
| 11/16″ | 0.042″ | 0.672″ | 0.651″ | 0.046″ | 0.027″ | 17,000 |
| 3/4″ | 0.042″ | 0.734″ | 0.712″ | 0.046″ | 0.027″ | 15,000 |
| 13/16″ | 0.050″ | 0.797″ | 0.773″ | 0.054″ | 0.031″ | 13,500 |
| 7/8″ | 0.050″ | 0.859″ | 0.833″ | 0.054″ | 0.031″ | 12,000 |
| 15/16″ | 0.050″ | 0.922″ | 0.894″ | 0.054″ | 0.031″ | 11,000 |
| 1″ | 0.050″ | 0.984″ | 0.955″ | 0.054″ | 0.031″ | 10,000 |
| 1-1/8″ | 0.050″ | 1.109″ | 1.078″ | 0.054″ | 0.031″ | 9,000 |
| 1-1/4″ | 0.062″ | 1.234″ | 1.198″ | 0.068″ | 0.035″ | 8,000 |
| 1-1/2″ | 0.062″ | 1.484″ | 1.443″ | 0.068″ | 0.035″ | 6,500 |
| 1-3/4″ | 0.078″ | 1.734″ | 1.688″ | 0.086″ | 0.042″ | 5,500 |
| 2″ | 0.078″ | 1.984″ | 1.933″ | 0.086″ | 0.042″ | 4,500 |
| 2-1/4″ | 0.093″ | 2.234″ | 2.178″ | 0.102″ | 0.050″ | 4,000 |
| 2-1/2″ | 0.093″ | 2.484″ | 2.423″ | 0.102″ | 0.050″ | 3,500 |
| 2-3/4″ | 0.109″ | 2.734″ | 2.668″ | 0.120″ | 0.058″ | 3,100 |
| 3″ | 0.109″ | 2.984″ | 2.913″ | 0.120″ | 0.058″ | 2,800 |
Internal Retaining Rings — Bore Sizes 3/8″ to 2-1/2″
Internal rings fit into a groove machined inside a housing bore. The free outside diameter is larger than the groove — the ring is compressed during installation and expands outward to seat.
| Bore Dia. | Ring Thick. | Free Dia. | Groove Dia. | Groove Width | Groove Depth | Max RPM |
|---|---|---|---|---|---|---|
| 3/8″ | 0.025″ | 0.394″ | 0.406″ | 0.028″ | 0.021″ | 32,000 |
| 7/16″ | 0.025″ | 0.457″ | 0.470″ | 0.028″ | 0.021″ | 28,000 |
| 1/2″ | 0.035″ | 0.520″ | 0.534″ | 0.038″ | 0.023″ | 24,000 |
| 9/16″ | 0.035″ | 0.583″ | 0.598″ | 0.038″ | 0.023″ | 21,000 |
| 5/8″ | 0.042″ | 0.646″ | 0.662″ | 0.046″ | 0.027″ | 19,000 |
| 11/16″ | 0.042″ | 0.709″ | 0.726″ | 0.046″ | 0.027″ | 17,000 |
| 3/4″ | 0.042″ | 0.771″ | 0.790″ | 0.046″ | 0.027″ | 15,000 |
| 7/8″ | 0.050″ | 0.896″ | 0.917″ | 0.054″ | 0.031″ | 12,000 |
| 1″ | 0.050″ | 1.021″ | 1.044″ | 0.054″ | 0.031″ | 10,000 |
| 1-1/8″ | 0.050″ | 1.146″ | 1.170″ | 0.054″ | 0.031″ | 9,000 |
| 1-1/4″ | 0.062″ | 1.271″ | 1.296″ | 0.068″ | 0.035″ | 8,000 |
| 1-1/2″ | 0.062″ | 1.521″ | 1.548″ | 0.068″ | 0.035″ | 6,500 |
| 1-3/4″ | 0.078″ | 1.771″ | 1.800″ | 0.086″ | 0.042″ | 5,500 |
| 2″ | 0.093″ | 2.021″ | 2.052″ | 0.102″ | 0.050″ | 4,500 |
| 2-1/4″ | 0.093″ | 2.271″ | 2.303″ | 0.102″ | 0.050″ | 4,000 |
| 2-1/2″ | 0.109″ | 2.521″ | 2.555″ | 0.120″ | 0.058″ | 3,500 |
Metric Retaining Rings — ANSI B27.7 Metric Series / DIN 471
Metric-dimensioned rings for shafts and bores. Dimensions align with DIN 471 (shaft) and DIN 472 (bore) for most common sizes.
| Shaft Dia. (S) | Free Dia. (D) | Thickness (t) | Groove Dia. (G) | Groove Width (W) | Depth (d) |
|---|---|---|---|---|---|
| 4 | 3.60 | 0.25 | 3.80 | 0.32 | 0.10 |
| 5 | 4.55 | 0.40 | 4.75 | 0.50 | 0.13 |
| 6 | 5.45 | 0.40 | 5.70 | 0.50 | 0.15 |
| 7 | 6.35 | 0.60 | 6.60 | 0.70 | 0.20 |
| 8 | 7.15 | 0.60 | 7.50 | 0.70 | 0.25 |
| 10 | 9.00 | 0.60 | 9.40 | 0.70 | 0.30 |
| 12 | 10.85 | 0.60 | 11.35 | 0.70 | 0.33 |
| 15 | 13.80 | 0.90 | 14.15 | 1.00 | 0.43 |
| 16 | 14.70 | 0.90 | 15.10 | 1.00 | 0.45 |
| 18 | 16.65 | 1.10 | 17.00 | 1.20 | 0.50 |
| 20 | 18.35 | 1.10 | 18.85 | 1.20 | 0.58 |
ANSI B27.7 & ASME B18.27
North American standard for tapered retaining rings (inch series). Specifies dimensions for external and internal rings, groove design, and material requirements.
DIN 471 / 472 & JIS B 2804
DIN 471 for metric external (shaft) rings; DIN 472 for internal (bore) rings. JIS B 2804 covers Japanese C-type retaining rings. ISO 464 for rings used with rolling bearings.
GROOVE DESIGN
Retaining Ring Groove Design & Machining Tolerances
Getting the groove right is where most retaining ring failures begin. Follow these DFM guidelines when machining grooves for snap rings.
01
Groove Diameter Tolerances
ANSI B27.7 specifies +0.002/−0.004″ for sizes up to 0.250″, loosening to +0.015/−0.020″ for 1.562–3.000″. Our CNC turning centers hold ±0.001″ as standard.
02
Break Sharp Corners
A sharp internal corner creates stress concentration. Specify a 0.005–0.015″ radius at the groove root to reduce notch effects without compromising ring seating.
03
Surface Finish
Ring bears against the groove sidewall under thrust load. Ra 63 μin (1.6 μm) or better on the loaded sidewall prevents galling and ensures consistent load distribution.
04
Wall Thickness Check
Maintain at least 1.5× the groove depth in remaining wall thickness for steel parts. Verify the wall behind the groove can withstand operating loads.
05
Concentricity
Hold groove-to-bore/shaft concentricity within 0.002″ TIR. An off-center groove creates uneven ring engagement and reduces effective thrust capacity.
06
Internal Groove Clearance
For internal grooves in blind bores, ensure adequate tool relief behind the groove. Our DFM review advises on reachable groove locations for deep bores.
Groove Tolerances — ANSI Inch Series
Groove diameters and ring thickness tolerances vary with size. Reference these values when specifying dimensions on your drawing.
+0.002/−0.004″0.125–0.250″ groove dia.
+0.005/−0.010″0.551–1.023″ groove dia.
±0.002″Ring thickness 0.188–1.500″
Retaining Ring Material Selection
The ring material determines corrosion resistance, temperature capability, and fatigue life. Match the material to your application environment to prevent premature failure.
| Material | Common Grades | Corrosion Resistance | Max Temp | Typical Finish | Best For | Rel. Cost |
|---|---|---|---|---|---|---|
| Carbon Spring Steel | SAE 1060–1090, 65Mn | Low (requires coating) | ~200°C | Zinc plate, black oxide, phosphate | General industrial, automotive interiors, machinery | $ |
| Stainless 304 (A2) | SUS304, 1.4301 | Good — food grade | ~300°C | Passivated | Food processing, medical devices, electronics, marine above waterline | $$ |
| Stainless 316 (A4) | SUS316, 1.4401 | Excellent — chemical/marine | ~300°C | Passivated | Chemical processing, coastal/marine, pharmaceutical, harsh environments | $$$ |
| Beryllium Copper | Alloy 25, C17200 | Good | ~200°C | Plain | Non-sparking environments (oil & gas), electrical conductivity, magnetic resonance | $$$$ |
| Alloy Steel | 51CrV4, 6150 | Low (requires coating) | ~250°C | Zinc plate, phosphate | Heavy-load automotive, high-fatigue applications | $$ |
Design tip: For most general-purpose applications, carbon spring steel with zinc plating or black oxide is the cost-effective default. Specify 304 stainless when the assembly sees moisture or outdoor exposure. Move to 316 only when chemical resistance or saltwater immersion is required — the material premium is significant for larger ring sizes.
RETAINING RING TYPES
Retaining Ring Types — Quick Comparison
Not every application calls for a snap ring. Choose the right retaining ring type for your load, speed, installation access, and cost requirements.
Snap rings dominate general industrial use — but spiral retaining rings, E-clips, constant-section rings, and push-on rings each have advantages in specific applications. Match the type to your operating conditions.
Snap Ring / Circlip
C-Shape with Lug Holes
Axial installation with snap ring pliers. High thrust capacity, medium RPM suitability. Available in a wide range of standard sizes per ANSI and DIN. The default choice for most industrial assemblies.
Spiral Retaining Ring
1.5–3 Turn Flat Wire Coil
No lugs — uniform 360° profile. Very high RPM capability. Wind into the groove without tools. Ideal for high-speed spindles, turbine shafts, and precision rotary equipment above 10,000 RPM.
E-Clip
E-Shaped, 3 Prongs
Radial installation — push directly onto the shaft from the side. Ideal when axial access is blocked, such as retaining gears mid-shaft on a long assembly. Low to medium thrust capacity.
When to Switch from Snap Ring to Spiral Ring
If your application runs above 10,000 RPM, the snap ring’s protruding lugs create imbalance and windage. Spiral rings have no lugs — just a uniform 360° coil — making them the standard choice for high-speed spindles, turbine shafts, and precision rotary equipment. For low-speed, high-load applications, the standard snap ring remains the most cost-effective solution.
32,000 RPM3/8″ snap ring max
2,800 RPM3″ snap ring max
10,000+ RPMSwitch to spiral rings
RETAINING RING FAQs
Frequently Asked Questions
A retaining ring is the broad category: any fastener that fits into a machined groove to prevent axial movement. A snap ring (or circlip) is a specific type — C-shaped, tapered cross-section, with lug holes for plier installation. All snap rings are retaining rings; spiral rings, E-clips, and constant-section rings are also retaining rings but are not snap rings.
Measure three things: the shaft or bore diameter where the ring will sit (nominal size), the groove diameter (verify it matches the standard), and the ring’s free diameter (uninstalled). The shaft/bore diameter is the key lookup value — all other dimensions follow from it in the ANSI B27.7 or DIN chart.
Groove depth ranges from 0.010″ (small rings under 1/2″) to 0.058″ (rings around 3″) per ANSI standard. See the groove depth column in the chart above for your specific size. Deeper grooves increase thrust capacity but reduce wall thickness — balance both factors.
Not recommended for critical or safety-related applications. Removing a snap ring permanently deforms it — the lug area stretches and the ring loses preload when reinstalled. For non-critical, low-load assemblies, reuse may be acceptable if no visible deformation and still requires firm plier pressure. When in doubt, replace — rings are the cheapest component in any assembly.
Depends on diameter — smaller rings handle higher RPM. A 3/8″ external snap ring is rated to 32,000 RPM; a 3″ ring drops to 2,800 RPM. The limitation comes from centrifugal force overcoming tension and imbalance from lug protrusions. For applications above 10,000 RPM, switch to spiral retaining rings.
ANSI B27.7 / ASME B18.27 for inch-series tapered retaining rings in North America. DIN 471 for metric external (shaft) rings. DIN 472 for metric internal (bore) rings. JIS B 2804 for Japanese C-type rings. ISO 464 for rings used with rolling bearings.
Get Retaining Ring Grooves CNC Machined
Upload your CAD file for an instant quote on retaining ring groove machining. Our CNC turning centers hold groove diameter tolerances to ±0.001″ with Ra 32–63 μin surface finish — well within ANSI B27.7 and DIN 471/472 requirements. Free DFM review, CMM inspection reports, ISO 9001 & AS9100 certified. Parts ship in 3–7 days, no minimum order quantity.