Industrial MRO Reference Library · Technical Reference

Tapered Roller Bearings — Cone & Cup Numbers

Tapered roller bearings are sold as a cone (inner ring with rollers and cage) and a cup (outer ring), each with its own number. This sheet explains inch cone and cup part numbers and the basic metric tapered series.

Ref MRO-0005ABMA 19.2ISO 355

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

A tapered roller bearing has tapered rollers running between a tapered inner ring and a tapered outer ring. It carries heavy radial load and thrust load in one direction, so it is usually mounted in pairs. Wheel hubs, gearboxes and axles are common uses. The cone is the inner ring with the rollers and cage assembled. The cup is the separate outer ring. In inch sizes, cone and cup are numbered separately, and the pair is called a set. ABMA 19.2 covers inch tapered roller bearings. Metric tapered roller bearings follow ISO 355 and are usually sold as complete bearings.

How to identify

Read both parts. The cone number is stamped on the large end of the cone or the cage. The cup number is stamped on the cup face. A complete set is written cone/cup, for example a cone number followed by a slash and a cup number. Metric bearings carry one number, such as 30205, often with suffixes.

Inch part number elements

Element	What it tells you	Notes
Letter prefix	Duty series, from light to heavy	Common prefixes include LL, L, LM, M, HM, H and HH
Digits after the prefix	Series and angle, then the part	The series portion is shared by cones and cups that work together
Final two digits in the cone range	Identifies a cone	In ABMA prefixed numbering, cone numbers commonly end in the 30 to 49 range, such as 48 or 49. Older non-prefixed numbers follow other patterns; check the maker's catalog
Final two digits in the cup range	Identifies a cup	In ABMA prefixed numbering, cup numbers commonly end in the 10 to 19 range, such as 10 or 11
Set number	A brand's shortcut for a cone and cup pair	Set numbers are brand catalogs, not ABMA standard

Metric tapered series

Metric tapered roller bearings use series such as 302xx, 303xx, 320xx, 322xx, 323xx, 330xx, 331xx and 332xx. The last two digits are the bore code, read the same way as ball bearings: 05 x 5 = 25 mm, so a 30205 has a 25 mm bore. ISO 355 also defines an alphanumeric designation system for metric tapered bearings that some makers print alongside the basic number.

Key points

A cone and cup must be a matching pair from the same series. A cup from a different series may fit the housing but not the cone.
Replace cone and cup together. A new cone in a worn cup fails early.
Bearing set-up (endplay or preload) is set by the equipment maker's procedure. Follow it.
Brand set numbers are handy, but always confirm the cone and cup part numbers they stand for.

Common mistakes

Ordering only the cone when the cup is worn.
Cross-referencing by bore alone. Many cones share a bore but have different cups and widths.
Treating a set number from one brand as a universal number.
Mixing an inch cone with a metric cup of similar size.

Governing standards: ABMA 19.2 (tapered roller bearings, inch design); ISO 355 (metric tapered roller bearings). Manufacturer catalogs for interchange.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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