Retaining Ring Groove Dimensions Chart: DIN 471/472 & ANSI Circlips
When turning an external shaft retaining ring groove (DIN 471 / ANSI Series 5100) or internal housing bore groove (DIN 472 / Series 5000), the groove width must carry a unilateral plus tolerance (+H13), bottom corner radii must not exceed 0.1 × ring thickness, and the outer edge margin must be at least three times the radial groove depth (Y ≥ 3d).
🔄 Interactive Internal & External Retaining Ring (Circlip) Groove & Thrust Load Calculator
Lookup standard groove diameter (D_g), width (W), radial depth (d), minimum safe edge margin (Y = 3d), and groove wall yield thrust capacity for DIN 471/472 and ANSI B27.7 snap rings.
How Do DIN 471/472 and ANSI B27.7 Retaining Ring Grooves Carry Axial Thrust Loads?
Tapered-section retaining rings (commonly called circlips or Truarc / Rotor Clip snap rings) governed by ANSI Engineering Standards Webstore (ANSI B27.7), DIN 471 (external shaft rings), DIN 472 (internal bore rings), and Machinery's Handbook (Industrial Press) provide a compact axial shoulder to lock ball bearings, gears, and Press-Fit Bushings without machining expensive stepped shaft shoulders or threading locknuts. Because the spring-steel ring (hardened to 47–53 HRC) snaps radially into a precision flat-bottomed lathe groove of radial depth d = |D_nominal - D_groove| / 2, any axial thrust load is resisted by two distinct structural failure modes: Ring Shear through the hardened spring thickness s, and Groove Wall Yielding of the softer parent shaft or housing metal.
In 90% of machine design applications using unhardened carbon steel (1018/1045) or 6061-T6 aluminum shafts (see our ISO 286 Shaft Tolerance Calculator), the softer groove wall yields long before the hardened spring steel ring shears! According to NASA Fastener & Mechanical Design Manual (NASA RP-1228) and ASME Geometric & Mechanical Standards mechanical design equations, the allowable static thrust load limited by groove wall compressive yielding with a safety factor SF = 2.0 is:
P_groove_allowable = (π × D_nominal × d_groove × S_yield_shaft) / SF
To prevent the thin outer lip of metal between the groove and the end of the shaft from shearing out like a shear pin, you must maintain a minimum axial Edge Margin of Y_min = 3 × d_groove.
| Nominal Size (D) | Ring Thickness (s) | Groove Width m (+H13) | DIN 471 Shaft Groove d_2 | DIN 472 Bore Groove d_2 | Radial Depth (d) | Min Edge Margin (Y=3d) | Action |
|---|---|---|---|---|---|---|---|
| 10.0 mm | 1.00 mm | 1.10 mm (+0.14/0) | 9.60 mm | 10.40 mm | 0.20 mm | 0.60 mm | |
| 12.0 mm | 1.00 mm | 1.10 mm (+0.14/0) | 11.50 mm | 12.50 mm | 0.25 mm | 0.75 mm | |
| 15.0 mm | 1.00 mm | 1.10 mm (+0.14/0) | 14.30 mm | 15.70 mm | 0.35 mm | 1.05 mm | |
| 20.0 mm | 1.20 mm | 1.30 mm (+0.14/0) | 19.00 mm | 21.00 mm | 0.50 mm | 1.50 mm | |
| 25.0 mm | 1.20 mm | 1.30 mm (+0.14/0) | 23.90 mm | 26.20 mm | 0.55 mm | 1.65 mm | |
| 30.0 mm | 1.50 mm | 1.60 mm (+0.14/0) | 28.60 mm | 31.40 mm | 0.70 mm | 2.10 mm | |
| 40.0 mm | 1.75 mm | 1.85 mm (+0.14/0) | 37.50 mm | 42.50 mm | 1.25 mm | 3.75 mm | |
| 50.0 mm | 2.00 mm | 2.15 mm (+0.14/0) | 47.00 mm | 53.00 mm | 1.50 mm | 4.50 mm |
Why Must Circlip Grooves Have Sharp Bottom Corners and Unilateral Plus Width Tolerances?
When programming a CNC lathe grooving cycle for a retaining ring, toolmakers must avoid using standard turning inserts with 0.4 mm or 0.8 mm nose radii! Because stamped circlips have a sharp inner corner (and must be installed with the sharp stamped burr edge facing away from the load-bearing groove wall), a large fillet radius at the bottom of the lathe groove prevents the ring from seating flat against the vertical load wall, causing the ring to dish conically and pop out under vibration. Always use a dedicated flat-bottomed precision grooving insert whose corner radius is under 0.1 × s (typically ≤ 0.10 mm or 0.004") and verify surface finish on our Surface Finish Ra to Rz Converter and ANSI B17.1 Keyway Calculator per NIST (National Institute of Standards and Technology) and ISO International Metrology Standard metrology protocols.
| Shaft / Bore Dia | External Part # | Ext Groove Dia | Internal Part # | Int Groove Dia | Groove Width (W) | Groove Depth (d) | Min Edge Margin (3d) |
|---|---|---|---|---|---|---|---|
| 1/4" (0.250") | 5100-25 | 0.230" (±0.0015") | 5000-25 | 0.268" (±0.001") | 0.029" (+0.003") | 0.010" | 0.030" |
| 3/8" (0.375") | 5100-37 | 0.352" (±0.002") | 5000-37 | 0.397" (±0.002") | 0.029" (+0.003") | 0.0115" | 0.035" |
| 1/2" (0.500") | 5100-50 | 0.468" (±0.002") | 5000-50 | 0.530" (±0.002") | 0.039" (+0.003") | 0.016" | 0.048" |
| 3/4" (0.750") | 5100-75 | 0.704" (±0.003") | 5000-75 | 0.796" (±0.003") | 0.046" (+0.003") | 0.023" | 0.069" |
| 1.000" (1") | 5100-100 | 0.940" (±0.003") | 5000-100 | 1.066" (±0.003") | 0.046" (+0.003") | 0.030" | 0.090" |
| 1-1/2" (1.500") | 5100-150 | 1.406" (±0.004") | 5000-150 | 1.594" (±0.004") | 0.056" (+0.004") | 0.047" | 0.141" |
When turning DIN 471 or DIN 472 retaining ring grooves on a CNC lathe, tool selection directly governs the axial fatigue life of the shaft. While the thrust-bearing groove wall must remain strictly perpendicular (90°) to the shaft axis with a sharp top edge to prevent ring cam-out under axial shock loads, the bottom root corners of the groove should carry a controlled tool nose radius of R_max = 0.1 × t to minimize geometric stress concentration factors (K_t).
To eliminate axial end-play (backlash) in precision ball screw assemblies and gearbox bearing stacks, specify beveled retaining rings (Truarc Series 5102 / N5002) or bowed wave-spring circlips (DIN 471L / Series 5101). A 15° beveled circlip wedges into a matching 15° angled groove wall under its own radial spring tension, automatically taking up up to 0.010" (0.25 mm) of cumulative bearing race and housing tolerance stack-up without requiring precision ground shim packs.
During high-RPM spindle operation, external shaft retaining rings experience outward centrifugal force that reduces their radial grip in the groove bottom diameter (d2). Whenever a shaft rotates above 3,000 RPM, verify the manufacturer limiting speed rating or switch to a self-locking two-part balanced ring or threaded bearing locknut (DIN 981 KM/MB series) so centrifugal expansion cannot unseat the circlip during emergency spindle deceleration.
Frequently Asked Questions About Retaining Ring and Circlip Groove Machining
Which way should the sharp stamped edge of a retaining ring face during assembly?
Because retaining rings are stamped from flat spring-steel strip in a punch press, one face has a slight die-roll radius while the opposite face has a crisp 90° sheared edge; always orient the crisp sheared edge facing the outer load-supporting groove wall (away from the retained bearing or gear) for maximum thrust capacity.
Why is retaining ring groove width toleranced +0.14 / -0.00 mm (H13) instead of bilateral ± tolerance?
If a groove is machined even 0.02 mm narrower than the maximum ring thickness, the circlip will bind and fail to snap into the bottom of the groove, leaving it unseated and creating a severe safety hazard under axial load.