Metric Stainless Steel Internal Retaining Rings
What are metric internal retaining rings? Metric internal retaining rings are tapered stainless spring rings sized to millimeter bore diameters rather than inch fractions, seating in grooves machined to the DIN 472 specification. They compress into the bore with internal pliers and spring outward into the groove. Metric sizing is a fit requirement rather than a preference, because a DIN 472 groove is cut to a millimeter groove diameter and width that an inch ring will not match. AlbanyCountyFasteners.com stocks metric stainless internal retaining rings from 13mm through 46mm.
What size internal retaining ring fits a metric bore?
Order by the bore diameter in millimeters, then check it against the groove. Substitution is tempting here because the numbers land close: a 26mm bore is 1.024 inches, so a 1 inch ring looks workable on paper. It is not, because DIN 472 specifies the groove diameter and groove width to metric dimensions, and an inch ring seats against those surfaces with reduced contact or binds before it expands fully. An internal ring that has not sprung completely into its groove will push out under thrust. If you are working on an imported gearbox, a European pump, or anything built to metric drawings, match the ring to the bore in the units it was machined in.
Why choose metric stainless internal rings
- Correct fit in DIN 472 grooves, where inch substitutions seat poorly or bind on the way in
- Matches the metric groove diameter and width already machined into imported housings
- Stainless resists corrosion in enclosed bores where condensation collects
- Tapered section keeps the shoulder height even around the full circumference
- Standard lug holes for controlled installation with internal retaining ring pliers
Metric sizes and specification
- Bore sizes including 13mm, 22mm, 26mm, 30mm, 37mm, 42mm, and 46mm
- DIN 472 is the standard covering internal rings for bores and their groove dimensions
- DIN 471 is the external counterpart, covering rings for metric shafts
- Verify the groove diameter and groove width, not just the bore, before ordering
Where metric rings are needed
- Imported machinery from Europe and Asia, and their replacement parts
- Metric gearbox, gear motor, and drive housings
- Hydraulic and pneumatic cylinders built to metric bore sizes
- Motorcycle, scooter, and small engine cases
- Industrial pumps, blowers, and rotating equipment on metric housings
- Any repair where the ring you removed came out of a metric bore groove
For inch bores, see our stainless steel internal retaining rings. Background on compression installation, taper, and groove requirements is on our internal retaining rings page.
Related Categories
- Internal Retaining Rings
- Stainless Steel Internal Retaining Rings
- Black Phosphate Internal Retaining Rings
- External Retaining Rings
- E-Style Retaining Rings
Metric Internal Retaining Ring FAQs
What is DIN 472?
DIN 472 is the German standard covering internal retaining rings for bores, specifying both the ring dimensions and the groove they seat in. DIN 471 is the matching standard for external rings on shafts. If your equipment drawing calls out a DIN number, it tells you the ring pattern and the groove specification the housing was machined to.
Can I use an inch ring in a metric bore?
Not reliably. The nearest inch size is usually off enough that the ring binds before expanding fully or seats with reduced contact against the groove. Incomplete seating is the most common reason internal rings push out under thrust.
How do I measure a metric bore groove?
Measure the bore diameter, the groove diameter at its base, and the groove width. Compare all three against the ring specification. Measuring only the bore can mislead you if the groove was cut to a non-standard depth or has worn from a previous ring working in it.
Are metric internal rings shaped differently from inch rings?
Functionally no. Both are tapered, lug-holed rings that compress into a bore and spring outward into a groove. The difference is dimensional, with metric rings built to millimeter bore diameters and DIN 472 groove specifications.
Do I need special pliers for metric internal rings?
Standard internal retaining ring pliers work. Match the tip diameter to the lug hole size in the ring, which depends on the ring size rather than whether it is metric or inch. Tips that are too small cam out and can elongate the lug holes.
What if my metric bore size is not listed?
Contact us with the bore diameter and the groove dimensions from your parts diagram. Metric ring sizes follow the DIN 472 progression and we can confirm availability or identify the correct part for your assembly.