Circlip Calculator DIN 471/472
Determine groove dimensions for shaft (DIN 471) and bore (DIN 472) retaining rings directly from the nominal diameter and verify the groove against bearing (contact) pressure: from the axial force, groove geometry and the yield strength of the adjoining shaft/hub material follow the actual pressure, the allowable pressure and a traffic-light rating, live with every input.
Calculation
Model: simplified bearing-pressure check of the groove (static load), no ring own load capacity, tilting or speed limit. Sizing tool for mechanical engineering.
Results
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Formulas and fundamentals
Groove dimensions per DIN 471 and DIN 472
For each nominal diameter d1 (shaft or bore diameter) the standard fixes the groove diameter d2, the ring thickness s, the groove width m (tolerance class H13) and the minimum edge distance n. For a shaft ring (DIN 471) the groove is cut into the shaft, so d2 is smaller than d1; for a bore ring (DIN 472) the groove is cut outward into the bore wall, so d2 is larger than d1.
Projected bearing area and contact pressure
The axial force F is transferred from the adjoining part (e.g. a bearing ring, gear, or bushing) through the ring face into the groove flank of the shaft or bore. The projected bearing area is approximated as the annulus between the nominal and the groove diameter:
This gives the contact pressure:
Allowable pressure and traffic-light rating
The allowable contact pressure follows from the yield strength Re of the shaft/hub material (not the ring itself) and the required safety factor S:
The tool rates it: p ≤ 0.8·p_allow green (pass, comfortable margin), p ≤ p_allow amber (marginal), p > p_allow red (fail - the groove flank yields permanently).
Model limitations
This check covers only the bearing pressure of the groove - a simplified, static model. Not included: the notch effect of the groove on the shaft's own fatigue strength (use the shaft calculator per DIN 743 with the matching notch case for that), the ring's own load capacity F_R, and the tilting and rotational speed limits of the ring, which are manufacturer-specific (retaining ring catalog, e.g. Seeger-Orbis) and are not modeled here because they depend on the specific ring geometry and batch. If the adjoining part does not have a sharp edge but a radius or chamfer instead, the effectively usable bearing area shrinks and the load capacity drops noticeably; in that case the edge distance n should additionally be checked against the catalog.
Worked example
Given: a shaft retaining ring per DIN 471 with nominal diameter d1 = 25 mm sits on a shaft made of C45 (Re = 370 N/mm²) and supports a part with an axial force F = 5000 N. Required safety factor S = 1.5, the contact is sharp-edged.
Groove dimensions DIN 471, d1 = 25: groove diameter d2 = 23.9 mm, ring thickness s = 1.2 mm, groove width m = 1.3 mm, edge distance n = 1.7 mm.
Projected bearing area A = pi/4 · (25² − 23.9²) = pi/4 · (625 − 571.21) = 42.25 mm². Contact pressure p = 5000/42.25 = 118.4 N/mm².
Allowable pressure p_allow = Re/S = 370/1.5 = 246.7 N/mm², 80% of that is 197.3 N/mm². Since p = 118.4 N/mm² is below that, the tool rates the check green (pass) - a clear margin against the allowable contact pressure.
Frequently asked questions
Where do the groove dimensions for retaining rings come from?
The groove dimensions (groove diameter d2, ring thickness s, groove width m, minimum edge distance n) are standardized in DIN 471 (shaft rings) and DIN 472 (bore rings) and are listed per nominal diameter in mechanical engineering reference tables (e.g. Roloff/Matek). The tool uses these standard values directly; it does not size the groove geometry itself.
How much axial force can a retaining ring withstand?
There is no single blanket figure - two separate limits apply. First, the contact pressure in the groove, which depends on the yield strength of the shaft/hub material (that is what this tool checks). Second, the ring's own load capacity F_R (bending/expansion of the open ring), which varies by ring geometry and manufacturer and must be looked up in the retaining ring catalog (e.g. Seeger-Orbis). The actual allowable axial force is the smaller of the two.
What does a sharp-edged contact mean?
The standard load capacity values assume a sharp-edged (90°) contact face on the mating part, so the full ring face is available for load transfer. If the adjoining part has a radius or chamfer instead, the effective contact area between ring and part shrinks - the actual load capacity drops accordingly, and the edge distance n should additionally be checked.
Retaining ring versus shaft nut or set collar - which is better?
Retaining rings are compact, light and inexpensive, but their axial capacity is limited by contact pressure and the ring's own load capacity, and the groove weakens the shaft. Shaft nuts or set collars with a clamping screw transfer significantly higher axial forces without wear or a notch effect, but need more installation space and either a thread or a clamped connection. For high axial forces or safety-relevant applications, shaft nuts are usually the more robust choice.
Is there a rotational speed limit for retaining rings?
Yes - at high rotational speeds, centrifugal force tends to expand the open ring, weakening its seating in the groove and hence its load capacity. The allowable limit speed is manufacturer-specific (depending on ring mass, geometry and material) and is deliberately not calculated here - consult the manufacturer's retaining ring catalog.
Does the groove weaken the shaft?
Yes, every groove is a notch and noticeably reduces the shaft's fatigue strength at that location. This tool only checks the bearing pressure of the groove, not the notch effect on shaft strength. For the shaft's fatigue verification with the retaining-ring-groove notch case, use the shaft calculator per DIN 743.
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