📌 Quick read: If you spec bearings for OEM equipment or run a maintenance/procurement desk at a plant, this handbook will save you about three months of trial and error. We’ve reorganised the high-frequency models we ship into a “family × application” map covering everything from 305 micro-motor bearings to 29488 vertical-mill giants. ISO cross-references and an FAQ for the most common selection questions are at the end.
#bearing selection#industrial bearings#spherical roller#deep groove ball#thrust bearing#GB designation
📑 Table of Contents
- Why the wrong bearing spec costs seven figures
- The five bearing families at a glance
- Volume champions: small/micro deep groove ball bearings (305/307/309)
- Industrial workhorses: medium deep groove ball bearings (311/313/315/318)
- Heavy general-purpose: large deep groove ball bearings (319/326/6026/6230/6236L)
- Drivetrain core: spherical roller bearings (2217/2218/22224/2230)
- Specialty heavy-duty: metallurgy & mining bearings (3086313/29488/66412/66432/46416)
- Specialty thrust: equipment-specific spares (9039428/9039352)
- Selection in practice: a 4-step workflow
- Why work with ZQM Bearings
- FAQ
1. Why the wrong bearing spec costs seven figures
A single unplanned shutdown on a rolling mill costs somewhere between $70k and $300k in lost production, plus 30% emergency procurement premium and missed delivery penalties. When post-mortems trace the failure back to “the wrong bearing was specified”, the conversation gets very quiet very fast.
Across 12 years and 200+ industrial customers — steel mills, mines, motor and gearbox makers, crane and cement operators — we’ve found that over 70% of bearing failures are not quality issues. They’re selection issues. The usual suspects:
- A deep groove ball bearing installed in a heavy-shock position → early subsurface fatigue, 3–6 month life.
- A standard-tolerance spherical roller bearing on a spindle → vibration out of spec, life cut in half.
- An open bearing run in dusty or wet conditions → raceway wear, life drops from 20,000 h to 3,000 h.
- Substituting a new-designation bearing for an old GB code on legacy equipment → same bore, but the flanges don’t line up, and it won’t seat.
Bearing selection is application-driven, not catalogue-driven. The rest of this guide walks through 22 of our most-shipped models by family and application boundary.
2. The five bearing families at a glance
Before drilling into individual part numbers, here is the framework. All 22 models in this article fall into one of the five families below.
| Family | Typical code | Load profile | Typical applications | Models in this guide |
|---|---|---|---|---|
| Deep Groove Ball Bearing (DC) | 6xxx dominant | Light–medium radial + minor axial; high speed capability | Motors, pumps, fans, appliances | 12 |
| Spherical Roller Bearing (SRB) | 2xxx dominant | Heavy radial + moderate axial; self-aligns 1.5°–2.5° | Gearboxes, rolling mills, vibrating screens, mining | 4 |
| Thrust Spherical Roller (TSRB) | 294xx etc. | Very heavy axial + heavy radial | Vertical mills, marine propellers, cement mills | 1 |
| Tapered Roller Bearing (TRB) | 3xxxx (old: 6xxxxx) | Heavy radial + heavy axial; single row can take pure axial | Mill roll necks, gearboxes, wheel hubs | 1 |
| Thrust / Combined Bearing | 9039xxx, 664xx etc. | Axial-dominant; combined load configurations | Mill screw-down, cranes, injection moulding | 4 |
Framework in mind — let’s get into the actual models.
3. Volume champions: small/micro deep groove ball bearings (6305/6307/6309)
These three bearings (old codes 305 → 6305, 307 → 6307, 309 → 6309) are the highest-volume, lowest-cost, broadest-coverage SKUs in the entire deep groove ball family. Several ZQM customers run them through at the thousand-per-month level.305 (6305) — Small deep groove ball / 25 × 62 × 17 mm
The standard fit on micro-motors and consumer-grade equipment — washing-machine motors, extractor fans, power tools, office machines. Low unit price, high install base. Treat it as a “safety stock” SKU — keep 1.5–2× monthly consumption on the shelf.307 (6307) — Small deep groove ball / 35 × 80 × 21 mm
The “traffic driver” for small motors, power tools, farm machinery, conveyor systems. Very high volume, low unit price — a strong fit for e-commerce channels (Alibaba, Made-in-China, Amazon Business, etc.).309 (6309) — Small/medium deep groove ball / 45 × 100 × 25 mm
The volume leader for general-purpose motors, pumps, farm equipment, textile machinery. One load step up from 307 in radial capacity. Runs just behind 307 in volume — the plant MRO “hard currency”.
Selection tip: This group is also the one most exposed to cheap, off-brand product. For continuous-duty industrial use, insist on P0/P6 tolerance and a recognised manufacturer (SKF, FAG, NSK, NTN, or a Tier-1 domestic brand). Cage strength, clearance control, and ball roundness are exactly where counterfeit or low-grade bearings fail first.
4. Industrial workhorses: medium deep groove ball bearings (6311/6313/6315/6318)
If 305–309 are the “volume champions”, 311–318 are the backbone of any industrial MRO inventory. About 90% of standard industrial motors, gearboxes, pumps, fans, and compressors use this size range. They are also the deepest part of ZQM’s stock.
| Model | ISO code | Key size (d × D × B) | Typical applications | Positioning |
|---|---|---|---|---|
| 311 | 6311 | 55 × 120 × 29 mm | Standard motors, gearboxes | Volume / commodity |
| 313 | 6313 | 65 × 140 × 33 mm | Industrial standard motors | Volume / commodity |
| 315 | 6315 | 75 × 160 × 37 mm | Standard motors, pumps | Volume / commodity |
| 318 | 6318 | 90 × 190 × 43 mm | Industrial motors, gearboxes | High volume / volume-margin |
The real differentiator in this group is the trade-off between radial load capacity and limiting speed. For example, 6318 carries roughly 1.5× the dynamic load of 6315, but its limiting speed drops from 6,300 rpm to 4,500 rpm. Bigger is not always better — match the envelope to the duty cycle.
Selection tip: For motors and pumps running 24/7 under meaningful vibration (fans, crushers, hammer mills), upgrade from P0 to P6 tolerance. Real-world life extension is typically 30%–50%.
5. Heavy general-purpose: large deep groove ball bearings (6319/6326/6026/6230/6236L)
Once you cross ~60 mm bore, the role of a deep groove ball bearing changes. These are no longer just “motor bearings” — they become heavy-equipment general-purpose spares. Unit prices step up from tens of dollars to hundreds, and gross margin opens up significantly.
| Model | ISO code | Key size (d × D × B) | Typical applications | Positioning |
|---|---|---|---|---|
| 319 | 6319 | 95 × 200 × 45 mm | General machinery, gearboxes | Common large / mid-high margin |
| 326 | 6326 | 130 × 280 × 58 mm | Heavy motors, pump industry | Common large / high margin |
| 6026 | — | 130 × 200 × 33 mm | Motors, fans (thin-section / light) | Common large / mid margin |
| 6230 | — | 150 × 270 × 45 mm | Heavy general equipment | High value / high margin |
| 6236L | — | 180 × 320 × 52 mm | Heavy motors, centrifuges | Common large / high margin |
6026 is the easy-to-miss SKU in this group: it is a thin-section 62-series bearing (only 33 mm wide), specifically designed for large bore but limited radial envelope — vertical motors, fans, transmissions. If your drawing calls for “large bore 6-series with restricted width”, 6026 is usually a better fit than 6326.
The “L” suffix on 6236L denotes a machined brass cage. Compared with standard pressed-steel or polyamide cages, brass tolerates higher speeds and higher operating temperatures — which is why it is the default for heavy motors and centrifuges under continuous high load.
Installation tip: For large deep groove ball bearings, always use hot mounting (oil bath at 80–100 °C). Cold pressing leaves brinelling marks on the raceway. For removal, use a hydraulic puller — never strike the ring with a hammer.
6. Drivetrain core: spherical roller bearings (2217/2218/22224/2230)
If deep groove ball bearings are “general purpose”, spherical roller bearings are the workhorse of industrial drivetrains. They cover the duty cycle that ball bearings can’t: heavy load + shock + shaft deflection.
The core construction is two rows of barrel-shaped rollers running in a spherical outer raceway. “Self-aligning” means the outer race is spherically machined, so when the shaft deflects 1.5°–2.5° or the housing is slightly misaligned, the bearing compensates automatically and avoids edge stress concentration on the rollers.2217 — Medium spherical roller / 85 × 150 × 36 mm
High-frequency spindle spare. Used on machine-tool spindles, mining drivetrains, large fan shafts. Steady demand at a comfortable mid-high margin — a rolling 30–60 day safety stock is a sensible baseline.2218 — Medium spherical roller / 90 × 160 × 40 mm
High-frequency auxiliary-shaft spare. Pairs with 2217, typically supporting the inboard or outboard end of a gearbox. Strong repeat-order pattern — sell it as a bundle with 2217.22224 — Large spherical roller / 120 × 215 × 58 mm
High-volume / core margin SKU. One of the highest-volume spherical roller SKUs we ship. Primary applications: heavy gearboxes, vibrating screens, mining feeders, agitators. On vibrating screens, 22224 is essentially the default fit.2230 — Large spherical roller / 150 × 270 × 73 mm
Mining & heavy drivetrain dedicated. Roughly 2× the dynamic load of 22224. Found on large ball mills, SAG mills, stacker-reclaimers, and port equipment. High value / high margin — single order values are large, but decision cycles are long.
Selection tip: Lubrication is the make-or-break factor for spherical roller bearings. In heavy, low-speed applications we recommend EP2 / EP3 extreme-pressure lithium grease, with provision for an auto-lube port on the housing. In dusty environments, use labyrinth seals + a flinger disc, not a simple rubber contact seal.
7. Specialty heavy-duty: metallurgy & mining bearings (3086313/29488/66412/66432/46416)
Now we cross into “specialty” territory. This group is defined by legacy GB designations, high unit value, high margin, and specialised applications. If you’ve ever stared at a code like 3086313, 29488, or 66412 and wondered where it came from — these are pre-1993 Chinese national standard designations that are still in widespread use, especially in legacy equipment.
For any of the legacy codes below, when ordering, supply all three: the old GB code, the equivalent ISO / current code, and the bore × OD × width dimensions. Three data points remove almost all ambiguity.3086313 — Heavy / specialty double-row tapered roller bearing (legacy GB)
Rolling mill & mining dedicated. Niche / high margin. “30” = tapered roller, “86” = structural code, “13” ≈ 65 mm bore. Used on mill roll necks and crusher supports, often cross-referenced to the ISO 3513xx series. Always verify with the drawing and dimensions before substituting.29488 — Extra-large thrust spherical roller bearing
Giant equipment / vertical mills. The largest and most valuable model in this guide — single-unit price typically $7,000 – $22,000. Operating envelope: vertical mill grinding rollers, cement-mill roller presses, large marine rudder propulsors, ore crushers. Subject to hundreds of tonnes of axial load plus severe radial shock. Very high value / very high margin — every order deserves dedicated follow-up.66412 — Medium-large double-direction thrust / combined bearing (legacy GB)
Metallurgy / heavy industry. “66” = double-direction thrust ball bearing, “412” = structural code. Common in rolling mill screw-down nuts, vertical mill supports, crane slewing rings. Cages are typically brass or solid steel to absorb shock.66432 — Large double-direction thrust / combined bearing (legacy GB)
Heavy gearboxes / metallurgy. Same family as 66412, but larger. Specialty / high margin. Applications: large rolling-mill screw-down, mine-hoist gearboxes, metallurgical roller-table drives.46416 — Medium-large thrust tapered roller bearing (legacy GB)
Metallurgy / heavy industry. “46” = thrust tapered roller, “416” = structural code. Specialty / high margin. Used in rolling-mill roll-adjustment mechanisms, continuous-caster roller arrays, and mine-hoist axial positioning.
Selection tip: For very large bearings like 29488, we strongly recommend an on-site survey + equivalent-model evaluation. Our application engineers can do this at no charge — a small dimensional error here can derail a months-long spares plan.
8. Specialty thrust: equipment-specific spares (9039428/9039352)
9039428 — Specialty thrust / combined bearing (legacy GB)
Equipment-specific spare. “9039” is the prefix for large thrust ball bearings, “428” is the size code. Niche / high margin. Used in mine-hoist head sheaves, rolling-mill roll-shaft positioning, special crane slewing mechanisms. Lead time is typically 30–60 days — plan ahead.9039352 — Specialty thrust / combined bearing (legacy GB)
Equipment-specific spare. Same family as 9039428, but larger. Niche / high margin. Applications: large cranes, port equipment, special chemical-process machinery running heavy axial loads.
Selection tip: The 9039 series is “niche but essential”. For plants that can’t tolerate downtime, we recommend a strategic safety stock arrangement — when this bearing fails, there is usually no drop-in replacement on the shelf.
9. Selection in practice: a 4-step workflow
Twenty-two models later, let’s ground this in process. The 4-step workflow below covers about 80% of industrial selection scenarios:
- Step 1 — Lock down the three operating parameters. Load (radial / axial / combined, and magnitude), speed (limiting vs. operating rpm), and environment (clean / dusty / wet / hot / corrosive).
- Step 2 — Pick the family. Use the family table in section 2. Light-to-medium load at high speed → deep groove ball. Heavy load with shock and shaft deflection → spherical roller. Extra-heavy axial → thrust spherical roller. And so on.
- Step 3 — Narrow to one to three candidates within the family. Filter by bore, limiting speed, and envelope (d × D × B).
- Step 4 — Validate four boundary conditions. Operating temperature (drives clearance and cage material), lubrication method (grease / oil / oil-air), sealing (2RS / 2Z / open), mounting method (hot / cold / hydraulic).
If you still have questions after these four steps, the fastest path forward is to talk to the manufacturer’s application engineer — not to keep searching online. Two models that look interchangeable on paper can differ by an order of magnitude in real-world performance for your specific duty cycle.
10. Why work with ZQM Bearings
A quick word about us. ZQM Bearings is a specialist in industrial-spare bearings. Over 12 years, we’ve supported more than 200 plant customers across steel, mining, motors, gearboxes, cranes, cement, and chemicals. What we deliver is not just a catalogue — it’s selection support and accountability:
- ✅ Stock on all 22 core models — small sizes ship same day, large items (29488, 9039428, etc.) kept in strategic reserve.
- ✅ Dual designation support — old GB codes and current ISO codes handled side by side, so legacy drawings never block procurement.
- ✅ Free duty-cycle assessment + selection support — 1-on-1 application engineering, not a chatbot.
- ✅ Mill certificate + test report shipped with every order — third-party re-inspection welcome.
- ✅ OEM customisation — non-standard sizes, special materials, special clearances on request.
Need a quote or technical consultation on any of these 22 models?
Send us your duty cycle (equipment type, load, speed, bore) and we will return a selection recommendation and a quote within 24 hours.
📩 Email: [email protected] ｜ 🌐 Web: www.zqmbearings.com
11. FAQ
❓ Q1. What’s the difference between a deep groove ball bearing and a spherical roller bearing?
A: Deep groove ball bearings (6xxx series) primarily carry radial loads, run at high speeds, are simple in structure, and cost less — ideal for electric motors, pumps, and consumer appliances at moderate speeds. Spherical roller bearings (2xxx series) use two rows of barrel-shaped rollers and a spherical outer raceway. They carry heavy radial loads plus moderate axial load, and self-align by 1.5°–2.5°, tolerating shaft deflection and misalignment — the standard choice for gearboxes, rolling mills, and vibrating screens under shock loads.
❓ Q2. Can I still source bearings under old GB designations like 3086313, 66412, or 9039428?
A: Yes. While new designs use GB/T 272 or ISO designations, metallurgical, mining, and heavy-machinery plants still run equipment designed to legacy codes, so specialist bearing manufacturers keep moulds and stock for these. When ordering, supply the legacy GB code, the equivalent ISO code (if known), and the bore × OD × width (d × D × B) in mm to remove ambiguity.
❓ Q3. What type of bearing should I use in a vertical roller mill or rolling mill?
A: Vertical mill grinding rollers typically run on large thrust spherical roller bearings (e.g., 294xx series like 29488). Rolling-mill work rolls are usually supported on four-row or double-row tapered roller bearings (e.g., 3086313, equivalent to ISO 3513xx). Rolling-mill roll necks are commonly supported on large spherical roller bearings (22224 / 2230). Service life is long (8,000–20,000 hours), but a single unplanned shutdown costs multiples of the bearing price — use first-tier OEM product or a certified industrial equivalent.
❓ Q4. How should inventory strategy differ between high-volume commodity bearings and specialty high-margin bearings?
A: Commodity models (small deep groove ball bearings like 305/307/309/311/313/315) have low unit price and steady demand — best handled with high-turnover stock distributed through e-commerce or dealer networks. Specialty high-margin items (29488, 9039428, 66432, etc.) involve large single-order value, infrequent demand, and longer decision cycles — best handled with make-to-order production plus a strategic safety stock for key accounts. Slower turnover, materially higher gross margin.
❓ Q5. Beyond the part number, what other parameters matter when selecting an industrial bearing?
A: At minimum: basic dynamic load rating Cr, static load rating C0, limiting speed, clearance group (C2 / CN / C3 / C4), tolerance class (P0 / P6 / P5), cage material, seal type, and operating temperature range. ZQM Bearings lists all of these on every product datasheet — request it and cross-check before purchase.
❓ Q6. Can you cross-reference old drawing numbers to current ISO codes?
A: Yes. Send a photo of the equipment nameplate, the assembly drawing number, or the failed bearing itself. Our application engineering team will respond with the current ISO equivalent, dimensional verification, and a recommended substitute. Common legacy codes like 3086313, 66412, 9039428, 9039352, 29488, and 46416 are all on our standard cross-reference table.
Written by the ZQM Bearings engineering team, drawing on 12 years of industrial bearing supply experience.