Miniature & small ball bearings
Small size does not remove the need to specify load, closure and mounting tolerances.
On this page5 sections ⌄
Miniature bearing sizes, construction and handling
Start with a measured envelope and a complete part number. Micro, mini and miniature are size descriptions, not a guarantee of a particular construction, material or accuracy class.
What counts as a miniature bearing?
Manufacturers define their small-bearing ranges differently. NMB, for example, offers miniature ball bearings in chrome steel, stainless steel and proprietary corrosion-resistant materials, with open, shielded and flanged options. Treat the size label as a starting point, not a dimensional standard.
The searchable table here deliberately selects loaded deep-groove records with bore up to 10 mm and outside diameter up to 30 mm. Those are this table's search boundaries, not a universal definition of miniature. It is a snapshot of documented products, not a claim that every miniature product is included.
Read a miniature size chart without losing the variant
| Request | Record before searching | What must still match |
|---|---|---|
| 3 mm ID / bore | d = 3 mm, plus outside diameter D and width B | A bore alone can return several non-interchangeable series |
| 3×6×2.5 mm | d×D×B in millimetres; preserve the decimal | Exact width, closure and original designation |
| 4×8×3 mm / MR84ZZ | Keep the supplier's complete marking | A similar L-series marking needs a verified cross reference |
| 608ZZ, 8×22×7 mm | Basic envelope and shield description | Recorded material, clearance, lubricant and precision |
| Flanged miniature bearing | d, body D, B, flange diameter and thickness | The flange is not the bearing-body outside diameter |
| Inch miniature bearing | Original fraction or decimal for all dimensions | Convert with 25.4 mm/in; do not round to a metric size |
On a small screen, scroll the table horizontally.
These are instructions for interpreting requests, not claims that every requested variant is stocked or verified. The model table below supplies actual loaded dimensions. A missing result is a catalogue gap; it does not authorize inventing the dimensions or suffix.
Small bearings do not all carry the same loads
| Construction requested | Identify | Use the appropriate reference |
|---|---|---|
| Deep-groove ball | Radial rolling bearing; complete rings and ball set | Small-bore table below |
| Angular-contact | Contact angle, arrangement and axial load direction | Angular-contact family and preload requirements |
| Thrust ball | Axial washers and total assembly height | Thrust family; do not substitute radial width B |
| Needle / roller | Raceway, inner-ring provision and roller construction | Needle or roller family |
| Linear / guide rail | Shaft-guided motion or profiled rail carriage | Linear family and mounting interface |
| One-way / clutch | Locking direction and torque function | A free-running radial bearing is not a clutch |
| Pillow block / flange unit | Bearing plus housing and mounting pattern | Mounted-unit dimensions, not bore alone |
On a small screen, scroll the table horizontally.
Precision, speed and light-running behaviour
Specify dimensional/running accuracy, clearance, starting torque and running torque separately. NMB identifies preload, enclosure, lubrication and assembly as contributors to torque. More preload is not automatically better: excessive preload can increase heat and shorten useful life.
Compare rated speed at the stated lubrication and operating conditions. A long unloaded spin is not a measurement of ABEC class or loaded bearing life. Do not remove seals or reduce grease solely to improve a hand-spin test.
Mounting, removal and small bearing pullers
- Isolate the equipment and identify which ring has the interference fit; inspect shaft and housing seating surfaces.
- Use a square, aligned tool that acts on that ring's face. Keep installation force away from shields, seals and rolling elements.
- Apply controlled, continuous force rather than impact. Stop if the bearing cocks or the required force changes unexpectedly.
- For removal, record bore, access behind the ring and extraction clearance before choosing an internal puller, separator or press support. A tool advertised as micro or mini is not a fit specification.
- After assembly, check the specified rotation, endplay/preload and running behaviour before returning the equipment to service.
NMB warns that thin bearing rings can follow shaft or housing distortion. This checklist does not supply an equipment-specific press fit, puller size or mounting force.
Do not confuse small-bearing selection with equipment fitment
| Search term | Evidence still needed |
|---|---|
| Mini lathe / spindle | Machine model, spindle arrangement, load, speed, fit and preload specification |
| RC car, reel or Mini 4WD | Exact equipment version, bearing position and original complete designation |
| Mini bike / scooter / skate | Axle, hub, spacer stack, retention and actual duty |
| Mini Cooper / Mini One | Vehicle and component fitment; this is not a miniature-bearing classification |
| Bearing ball / loose ball | Ball diameter, material and ball grade, not assembled-bearing d×D×B |
On a small screen, scroll the table horizontally.
Search the recorded model candidates
1,012 loaded records in this table. Dimensions are d×D×B in mm. Filters narrow this snapshot immediately; open the exact product for its retained ratings and source description.
Table boundary: deep-groove descriptions, bore ≤10 mm and outside diameter ≤30 mm. It excludes other small-bearing structures and is not a universal miniature classification.
Showing 1–24 of 1,012 records. Filter or choose next to load more.
| Brand / full model | d×D×B (mm) | Original description | Closure | Clearance | Precision |
|---|---|---|---|---|---|
| KOYO 681 | 1×3×1 | Deep groove ball bearing | Open | Not reported | Not reported |
| KOYO F681 | 1×3×1 | Deep groove ball bearing | Open | Not reported | Not reported |
| SKF W 618/1 | 1×3×1 | Stainless steel deep groove ball bearing | Without | CN | Not reported |
| KOYO ML1003 | 1×3×1.5 | Deep groove ball bearing | Open | Not reported | Not reported |
| KOYO 691 | 1×4×1.6 | Deep groove ball bearing | Open | Not reported | Not reported |
| KOYO F691 | 1×4×1.6 | Deep groove ball bearing | Open | Not reported | Not reported |
| KOYO ML1204 | 1.2×4×1.8 | Deep groove ball bearing | Open | Not reported | Not reported |
| KOYO 68/1.5 | 1.5×4×1.2 | Deep groove ball bearing | Open | Not reported | Not reported |
| KOYO F68/1.5 | 1.5×4×1.2 | Deep groove ball bearing | Open | Not reported | Not reported |
| SKF W 618/1.5 | 1.5×4×1.2 | Stainless steel deep groove ball bearing | Without | CN | Not reported |
| KOYO W68/1.5 ZZ | 1.5×4×2 | Deep groove ball bearing | Shielded ZZ | Not reported | Not reported |
| KOYO WF68/1.5 ZZ | 1.5×4×2 | Deep groove ball bearing | Shielded ZZ | Not reported | Not reported |
| SKF W 638/1.5-2Z | 1.5×4×2 | Stainless steel deep groove ball bearing with integral sealing | Shield on both sides | CN | Not reported |
| KOYO 69/1.5 | 1.5×5×2 | Deep groove ball bearing | Open | Not reported | Not reported |
| KOYO F69/1.5 | 1.5×5×2 | Deep groove ball bearing | Open | Not reported | Not reported |
| KOYO W69/1.5 ZZX | 1.5×5×2.6 | Deep groove ball bearing | Shielded ZZ | Not reported | Not reported |
| KOYO WF69/1.5 ZZ | 1.5×5×2.6 | Deep groove ball bearing | Shielded ZZ | Not reported | Not reported |
| KOYO ML1506 | 1.5×6×2.5 | Deep groove ball bearing | Open | Not reported | Not reported |
| KOYO MLF1506 | 1.5×6×2.5 | Deep groove ball bearing | Open | Not reported | Not reported |
| KOYO WML1506 ZZX | 1.5×6×3 | Deep groove ball bearing | Shielded ZZ | Not reported | Not reported |
| KOYO WMLF1506 ZZ | 1.5×6×3 | Deep groove ball bearing | Shielded ZZ | Not reported | Not reported |
| SKF W 617/2 | 2×4×1.2 | Stainless steel deep groove ball bearing | Without | CN | Not reported |
| KOYO 682 | 2×5×1.5 | Deep groove ball bearing | Open | Not reported | Not reported |
| KOYO F682 | 2×5×1.5 | Deep groove ball bearing | Open | Not reported | Not reported |
Catalogue snapshot: 2026-10-01T16:36:30+00:00. Unknown properties are not inferred. This list is neither live availability nor replacement approval.
Questions to settle before selecting a model
Does a 3 mm bore identify the bearing?
No. Select outside diameter, width, construction and the complete suffix as well. The table can narrow the loaded records, but it does not approve interchangeability.
Is miniature the same as high precision?
No. Size and accuracy are separate attributes. Keep an unreported precision class unknown and verify the manufacturer's actual class.
Can I print a miniature bearing size chart?
Use your browser's Print / Save PDF on this page for the reference and currently displayed rows. The model table is a selection from the loaded catalogue, not a complete manufacturer catalogue.
Can I install a ceramic version wherever a small steel bearing fits?
Not from size alone. Ring material, fit, load, speed, lubrication and thermal behaviour need their own check. Use the ceramic and hybrid guide before treating it as a candidate.
Reviewed 2026-10-02. Technical basis: NMB miniature bearing range and Ball Bearing Engineering; BearingScope original manufacturer-record snapshot. Original BearingScope explanations and checklists. Product-specific approval remains necessary.
What to check
Start with the actual envelope
Use d, D and B rather than a marketing label such as micro or mini. The size finder includes sub-millimetre decimal dimensions when records exist.
Check handling and friction
Seal drag, lubricant quantity and mounting damage can be important in a small assembly. Do not rank bearings by unloaded spin time.
Read the complete part number
Metric and inch miniature series can look similar. Retain any flange, extended-ring or special-material designation.
Continue with real catalogue data
Preserve the full model, source description and unknown fields when making your shortlist. This reference website does not sell bearings or certify a replacement.
Related questions and tools
Thin-section & thin-wall bearing selection
A small cross section is a design characteristic, not a statement that every thin bearing is interchangeable.
Read and apply →Flanged bearings: ring flanges vs flanged housing units
A flange on a miniature bearing ring is not the same component as a two-bolt or four-bolt flanged housing.
Read and apply →Ceramic, hybrid & steel bearing selection
Separate rolling-element material from ring material and the complete bearing construction.
Read and apply →Stainless & corrosion-resistant bearing selection
A stainless label does not establish compatibility with every chemical, washdown or marine exposure.
Read and apply →Air & gas bearings: selection requirements and data limits
Air-film systems are not ordinary rolling bearings with an interchangeable part number.
Read and apply →Magnetic bearing systems: selection & comparison limits
A magnetic bearing is part of a rotor support and control system, not a simple size replacement for a ball bearing.
Read and apply →Hydrodynamic journal bearings & plain-bearing selection
A journal-bearing system depends on the sliding geometry and lubricant film, not a rolling-bearing L10 calculation alone.
Read and apply →Reference basis & data limits
Manufacturer terminology is retained in the product records. Technical reference basis: JTEKT Basic Bearing Knowledge (boundary dimensions, tolerance classes and lubrication); NSK Bearing ABCs (lubrication, designations and clearance); NTN technical FAQs (closure codes and component interchange); SKF rolling-bearing selection and maintenance references.
Selection workflows and catalogue grouping are BearingScope editorial aids. Verify the current drawing and application requirements before using a candidate. Missing database information is not converted into an assumed match.