Bearing Selection FAQ — Types, Sizes, Applications & OEM Service

The 6204 and 6205 share the same 62 series geometry but differ in size: 6204 is 20×47×14 mm (bore × OD × width), while 6205 is 25×52×15 mm. The 6205 therefore fits a 25 mm shaft versus 20 mm, has roughly 10% higher dynamic load capacity (about 14.0 kN vs 12.7 kN) and a slightly lower limiting speed. Choose 6204 where space and weight are tight; choose 6205 when the shaft is 25 mm or the load margin matters more than envelope size.

Both fit the same bore, but the 69 series is a thin-wall design. A 6900 measures 10×22×6 mm and weighs about 9 g, whereas a 6000 measures 10×26×8 mm at about 19 g: the 6900 saves 4 mm in OD, 2 mm in width and roughly 50% in weight, with a radial cross-section about 28% smaller. The trade-off is load: dynamic capacity is around 2.02 kN for the 6900 versus 4.58 kN for the 6000.

If the housing bore is fixed at 22 mm OD and radial load stays below 2 kN, specify the 6900. If the housing accepts 26 mm and you need the higher load margin, use the 6000. They are not interchangeable without re-machining the housing.

The 30205 and 30206 are both 02-series single-row tapered roller bearings (ISO 355 / GB T 297), differing by one size step. The 30205 is 25×52×16.25 mm with C_r about 32.2 kN and a grease limiting speed around 7,000 rpm; the 30206 is 30×62×17.25 mm with C_r about 34.2 kN and a grease limit around 6,000 rpm. Both have a contact angle near 14°.

The 30206 carries a slightly higher radial and axial load at the cost of a larger shaft (30 mm vs 25 mm) and lower speed. Always install tapered rollers in pairs or with a counter-bearing to support the thrust direction.

ZZ means two pressed-steel metal shields with a small non-contact gap; 2RS means two rubber contact seals. Metal shields run faster and cooler (the 6204ZZ limiting speed is roughly 23,000 rpm grease vs about 17,000 rpm for the 2RS) but allow fine dust and water past the gap. Rubber seals give far better protection against moisture and contamination but add friction and lower the speed limit.

Rule of thumb: ZZ for high-speed, clean and dry positions such as motors and fans; 2RS for wet, dusty or washdown environments. Both are pre-greased for life and are dimensionally interchangeable, but check that the 2RS fits within the lower speed limit.

Self-aligning ball bearings have a spherical outer race and tolerate shaft misalignment of roughly 1° to 3°, making them ideal for long shafts, agricultural equipment and conveyor idlers where alignment is poor. Deep groove ball bearings have no self-aligning capability and are sensitive to misalignment beyond about 0.5°, but they support higher speed, handle moderate axial loads in both directions and are more economical.

Choose self-aligning when shaft deflection or installation error is unavoidable; choose deep groove for high-speed, accurately aligned general machinery.

Both are single-row cylindrical roller bearings built for high radial load and high speed, with no significant axial capacity. The difference is rib location: the N type has two inner-ring ribs and no outer-ring ribs, allowing the outer ring to move axially in both directions; the NU type has two outer-ring ribs and no inner-ring ribs, allowing the inner ring to move axially in both directions.

Both suit floating (non-locating) positions and accommodate thermal shaft expansion, but the separable ring differs, which affects mounting and dismounting. For a fixed location with limited bidirectional thrust, use NJ or NUP instead.

For standard ISO dimension series (6000, 6200, 6300, 30200, NU/NJ/NUP etc.), the boundary dimensions are interchangeable, so a 6204 from any reputable manufacturer will mount in the same housing. Internal design, cage, grease, seal suffix and load ratings can differ, however.

Never assume interchangeability on clearance (CN vs C3), precision class (P0/P6/P5 or ABEC), seal type (2RS vs ZZ), contact angle or preload without checking the datasheet. For critical positions, match the original designation or have the supplier validate the equivalent in writing.

Radial internal clearance is the total radial movement of one ring relative to the other before load is applied, standardised by ISO 5753. CN (normal) is the default and is unmarked. C3 is greater than normal, while C4 and C5 are larger still; C2 and C1 are tighter.

C3 is specified when the bearing runs hot, has a tight interference fit on the shaft or operates at high speed, because both press fits and thermal expansion consume clearance during operation. Electric motors, generators and many gearbox positions commonly use C3 so the mounted, warmed-up bearing settles at a small positive operating clearance rather than going into preload.

ABEC (ABMA Std 20, from the Annular Bearing Engineering Committee) rates dimensional and running accuracy on a 1, 3, 5, 7, 9 scale. A higher number means tighter tolerance and lower runout, not higher load capacity. The approximate mapping to ISO 492 is ABEC 1 = P0 (normal), ABEC 3 = P6, ABEC 5 = P5, ABEC 7 = P4 and ABEC 9 = P2.

Most industrial machinery runs on normal or P6; P5 and P4 are typical for machine-tool spindles, while P2 is reserved for the most demanding precision spindles. Precision class is independent of internal clearance, so the two must be specified separately.

Chrome steel bearings use high-carbon chromium steel such as GCr15 / 52100, giving the best combination of hardness, fatigue life and cost for the vast majority of industrial uses. Stainless steel bearings (commonly AISI 440C for rings and balls, sometimes 316L for housings) trade some load capacity for corrosion resistance in wet, chemical, food, marine and washdown environments.

Stainless also costs more. Neither material is inherently better: choose chrome steel for dry, high-load and high-speed duty; choose stainless where rust or contamination is the dominant failure risk, and pair it with food-grade grease and FDA-compliant seals for food contact.

Preload is a deliberate, controlled compressive load applied to a bearing during installation to remove internal clearance. It is used on precision spindles and paired angular contact or tapered roller arrangements to reduce axial play, increase stiffness and improve running accuracy.

Preload is typically achieved with spring washers, spacers, locknuts or by grinding a bearing shoulder to a controlled dimension. Applying too much preload causes excess heat and shortens life, so the manufacturer's specified preload range should be followed.

The basic dynamic load rating (C) is the constant radial load a bearing can endure for a rating life of one million revolutions, used to calculate fatigue life under given operating conditions. The basic static load rating (C₀) is the maximum static load the bearing can carry without permanent deformation of the rolling elements or raceways exceeding a defined limit (commonly 0.0001 times the rolling element diameter).

For high-speed rotating parts, select by C and calculate L₁₀ life; for slow, oscillating or stationary-but-loaded parts, select by C₀ to avoid brinelling and deformation.

Lubrication interval depends on bearing type, speed, temperature and environment. Sealed-for-life bearings (2RS, ZZ) are pre-greased and generally require no re-lubrication during their service life. Open or re-greaseable bearings in normal conditions are typically re-greased every 3 to 12 months; in hot, wet or heavily contaminated environments, intervals shorten to weekly or monthly.

A practical rule is to fill the free space to about one-third to one-half with lithium or polyurea grease of the correct NLGI grade. Always follow the equipment and grease supplier recommendation, and do not mix incompatible greases.

The most common early warnings are unusual noise (grinding, clicking or rumbling), vibration or shaking, elevated operating temperature, and visible lubricant leakage or discolouration. Other signs include axial or radial play you can feel by hand, scoring or brinelling on the raceway, and metal particles in the grease.

Catching these early lets you replace the bearing during a planned stop instead of suffering a seized shaft or collateral damage to the housing and seal.

Store bearings in their original, undamaged packaging in a clean, dry, vibration-free place at 20–25°C and relative humidity below about 60%. Keep them flat rather than stacked, away from direct sunlight, dust, corrosive fumes and strong magnetic fields.

Do not remove anti-rust paper or open seals until mounting, and observe the first-in first-out principle. Grease and oil can age, so check the shelf life declared by the manufacturer before fitting long-stored bearings, especially for precision or sealed-for-life units.

Most centrifugal and general-purpose pumps use a pair of deep groove ball bearings on the pump shaft, commonly 6204 or 6305 in a 2RS sealed version to keep lubricant in and water and grit out. If the pump sees significant axial thrust (vertical pumps, mixed-flow designs), add an angular contact ball bearing or paired tapered rollers at the thrust side.

For submerged or heavily corrosive services, specify stainless steel rings, FKM or FDA-grade elastomer seals and NSF H1 grease. Standard guidance is C0 clearance for normal pumps and C3 for high-speed or hot-running units.

Conveyor idlers and pulleys are typically fitted with deep groove ball bearings for light to medium loads, or spherical roller bearings for heavy, shock-loaded or misaligned lines. In practice, many plants use housed units (pillow block / insert bearings) that include a sealed, self-aligning insert for easy installation and maintenance.

Apply a safety factor of about 1.5 to 2 times the calculated dynamic load, use multi-labyrinth or rubber-sealed closures in dusty conditions, and reserve axial-load or high-torque drive positions for tapered roller bearings.

Standard IE3 / IE4 electric motors most often use deep groove ball bearings from the 6000, 6200 and 6300 series, with the 6200 series (for example 6204, 6205, 6206) being the most common for small to medium frames. Motor applications favor low-noise, low-vibration grades with a glass-fibre nylon cage, and many specify C3 clearance to compensate for rotor heat growth and interference fits.

Shielded (ZZ or 2Z) versions are preferred for high speed and low torque; sealed (2RS) versions are chosen for dirty or humid environments, provided the lower speed limit is acceptable.

Agricultural machinery combines heavy, shock and vibrating loads with dust, mud and washdown, so favour sealed-for-life deep groove ball bearings, self-aligning ball bearings where shaft alignment is poor, and tapered or spherical roller bearings at high-load gearbox and wheel positions. Common sizes include 6204 to 6206 and the 6300 series.

Specify 2RS or multi-seal closures, C3 clearance for combined thermal growth and interference fits, and re-greaseable housings for conveyor and baler rollers. Confirm the exact model against the OEM parts list before replacing.

Mining equipment operates under heavy, shock and contaminated loads, so spherical roller bearings are widely used for crushers, vibrating screens, conveyors and gearboxes because they combine high radial and axial capacity with self-alignment. Tapered roller bearings suit wheel hubs and pinion shafts, while cylindrical roller bearings (NU, NJ, NUP) are common in high-speed gearbox and shaft-support positions.

Specify sealed or labyrinth closures, C3/C4 clearance for thermal growth, and schedule frequent re-lubrication with extreme-pressure grease. Every critical position should be validated against the OEM load and speed envelope.

Food and beverage bearings must prevent contamination and survive aggressive washdown. Key requirements are stainless steel rings and balls (AISI 440C or 316L), FDA-compliant elastomer seals, NSF H1-registered grease for incidental food contact, and a hygienic, easy-to-clean housing design.

Relevant frameworks include FDA 21 CFR, EU 1935/2004, NSF H1, 3-A and EHEDG depending on the market. Contact seals (2RS) are required because shielded (ZZ) versions allow wash water in; confirm chemical compatibility with the cleaning agents used in your plant.

Textile machinery commonly uses deep groove ball bearings for spindles, rollers and fans, angular contact ball bearings for high-speed precision spindle positions, and self-aligning ball or spherical roller bearings where shaft deflection and misalignment are unavoidable. Low-noise and low-vibration grades are important in spinning and weaving, and sealed-for-life versions reduce fibre contamination and maintenance.

The exact type and size must be matched to the spindle speed, load and the OEM specification, since textile machines vary widely between spinning, weaving, knitting and finishing.

Construction machinery combines heavy, shock and vibrating loads with dust, mud and wide temperature swings. Use tapered roller bearings for wheel hubs, pinion and axle positions; spherical roller bearings for heavy swing, undercarriage and gearbox positions; cylindrical roller bearings for high-speed shaft support; and deep groove ball bearings for auxiliary fans and pumps.

Specify C3/C4 clearance, high-load capacity, multi-seal or labyrinth closures and extreme-pressure re-greaseable housings, then validate each position against the equipment OEM load and speed envelope.

RAYSDE Bearing maintains a documented quality management system and material and heat-treatment controls that are verified against customer and order requirements. The specific certificates held for a given product line (such as ISO 9001, IATF 16949, or material and test reports) depend on the manufacturing site and series ordered.

For an up-to-date certificate list and valid copy of each certificate, please contact our sales team at [email protected] — we will issue the exact documents applicable to your order. Claims are limited to what can be verified by the issued certificate number and scope.

Yes. On request, RAYSDE can supply material traceability documents including material certificates (Mill Test Reports / EN 10204 2.1 or 3.1 as agreed), heat-number traceability, heat-treatment records and inspection reports. Availability depends on the product series and the agreed Incoterms, so please state the required standard (for example ISO 9001, ASTM, EN or customer-specific) when requesting a quotation.

For regulated industries such as food and automotive, full batch-level traceability can be arranged as part of the quality agreement.

Standard deep groove ball bearings are usually available from a few hundred pieces for common sizes, with the exact MOQ depending on the series, precision class, seal type and packaging. Modified clearance, special grease, stainless steel and custom markings carry a higher MOQ because of setup and minimum batch requirements.

Please send us the complete designation (for example 6204-2RS C3 P6) and required quantity, and we will confirm the applicable MOQ and unit price.

Lead time is typically 15–45 days depending on whether the item is in stock, the order quantity, customization and the agreed Incoterms. Standard sea freight, air freight and express courier are all available, and we can ship FOB, CIF, DAP or other terms as agreed.

For an exact delivery date and shipping method, please provide the destination port or address, required quantity and any documentation needs (such as certificate of origin or packing list) with your inquiry.

Yes, samples are available before bulk order. For standard sizes we can usually arrange a small quantity of free samples, with the customer covering the express freight; for custom specifications the sample may be charged at cost. Please confirm the complete bearing designation, quantity and delivery address, and we will issue a sample quotation.

Sample approval is recommended before mass production to verify fit, noise, running accuracy and packaging.

Yes. RAYSDE offers OEM and ODM service and can manufacture non-standard or custom bearings according to customer drawings or samples, including special dimensions, materials, clearances, greases, seals, cages, coatings and markings. The typical process is drawing review and quotation, sample production and approval, then mass production and inspection.

Please provide 2D/3D drawings, material and tolerance requirements and the required quantity so we can evaluate feasibility and MOQ.

RAYSDE is a bearing manufacturer and supplier producing deep groove ball bearings as its core product range, together with rolling bearings for industrial applications. The company serves motor, pump, fan, agricultural, conveyor, textile, construction and general machinery customers through both standard catalogue items and OEM/ODM custom production.

Products are supplied in bulk or as branded and private-label packaging, with quality documentation and global shipment arranged per the order requirements. Please contact us for the current product catalogue and manufacturing scope of your local RAYSDE entity.