Choose a machined brass cage when heavy loading, shock, or severe service dominates, and consider a ribbon steel cage when its construction is appropriate for the application.
The decision is not a generic material upgrade. Angular contact bearings typically use pressed steel cages, while machined brass, polyamide 46, and other designs serve defined duty envelopes [S4][S1].
Compare cage construction, load handling, and operating limits
A machined brass cage is used in vibration-sensitive applications, and two-part brass or steel cages are clamped together at assembly [S6]. Angular contact ball bearings generally use pressed steel cages, while polyamide resin and machined brass cages are also used [S4]. The suffix “M” identifies machined brass in the coding system described for angular contact bearings [S5].
A ribbon cage is a thin, formed steel separator that holds the balls apart, guides them around the raceway, limits rolling-element contact, and assists lubricant circulation [S1][S3].
For an angular contact bearing used in a pump, gearbox, or machine-tool spindle, the cage should be selected alongside contact angle, bearing series, lubrication, and preload, not by material label alone.
Use machined brass for robustness and controlled installation
For centrifugal pumps in petrochemical plants and oil refineries, the API advocates bearings with the “M” suffix, which denotes machined brass cages, although brass can smear and cause problems if light loading causes ball skidding [S5]. The suffix “M” has been used for machined-brass cage bearings in API-advocated centrifugal-pump selections for petrochemical plants and refineries [S5]. A machined cage is also preferred for vibration-sensitive applications in the cited Swiss bearing practice, where two-part brass or steel cages are identified by “Y” or “J” and machined brass by “M” [S6].
The robustness case includes installation tolerance. Brass is not universally immune to failure: under light loading that causes ball skidding, it can smear and create operating problems [S5]. Heavy radial or axial loading must still support proper rolling-element motion, correct preload, and adequate lubrication.
Machined brass cages also present chemical and thermal boundaries. These are material constraints on the cage, not permission to exceed the bearing’s own speed, temperature, or load ratings. For the related selection problem of high-speed angular contact cages, see angular contact cage selection for high dn operation.
Use ribbon steel for economical, low-inertia service
A ribbon cage is the practical choice when the duty is clean, lubrication is reliable, loads are moderate, and procurement cost matters. Pressed steel cages are economical, production-efficient, mechanically strong, and well suited to mass-produced bearings [S1]. In angular contact bearings, pressed steel is the normal cage option for many designs, including double-row 5xxx examples [S4].
It is also not a substitute for a polymer cage where lower friction, quiet running, and reduced centrifugal force are the governing requirements. Polyamide is listed among the common cage materials, and cage design helps ensure stable bearing operation at high speed [S1].
Two practical details remain bearing-specific. First, stamped riveted steel cages should not be used in centrifugal pumps because a detached rivet head can enter the raceway and cause immediate bearing failure [S5].
Match the cage to failure risks and service conditions
For a centrifugal pump with uncertain lubrication quality, hot installation, shock loading, or concern about degraded oil, specify machined brass with the “M” suffix after confirming the manufacturer supports that option [S5]. This comparison concerns installation exposure, not continuous operating temperature.
For a clean gear or conveyor drive with steady loading, favorable cooling, and no need for a heavy-section cage, use the manufacturer’s pressed or ribbon steel option to reduce cost. Stamped ribbon and stamped crown are two standard cage designs [S7]. In miniature high-speed instrument applications, a machined crown retainer may be more appropriate than either standard stamped ribbon or stamped crown designs [S7].
Do not select a machined brass cage above 300°C or in ammonia service [S3]. Do not select a riveted stamped cage for a centrifugal pump [S5]. Do not use a ball bearing merely because its bore and outside diameter match; contact angle, arrangement, load rating, speed, clearance, preload, lubrication, and cage code must all be checked.
Verify procurement and bearing-level limits
The cage decision should be recorded on the datasheet as a material and construction requirement, such as “machined brass, M suffix,” rather than as the vague instruction “heavy-duty cage.” NSK identifies pressed steel, Nylon-46, and machined-brass cage options for angular contact bearings, and notes that polyamide resin cages are sometimes used in high-precision bearings with contact angles of 30° or less [S4].
Do not transfer a cage choice from one bearing size or series to another without the manufacturer’s approval. For example, NSK’s comparison of a 5206 double-row bearing with a 7206ADB(M) bearing shows the same 30 mm bore and 62 mm outside diameter, but widths of 23.8 and 32 mm, dynamic ratings of 29.6 and 36.5 kN, static ratings of 21.1 and 29.5 kN, and oil limiting speeds of 9,500 and 13,000 min-1 [S4]. Equal principal dimensions do not make their cages or performance equivalent.
The final procurement record should also state lubricant type, contamination level, continuous operating temperature, installation-heating limit, radial and axial loads, target speed, preload, and any requirement for an M suffix. This prevents a procurement substitution from changing speed capability or environmental suitability without engineering review.