Bearing size reference
Miniature ball bearings: size tables
Small deep groove ball bearings with 3–9 mm bores — 608, 625, 688 and friends — used in skateboards, 3D printers, fans and small motors.
Miniature bearings are deep groove ball bearings with bores under 10 mm. Their designations use a single-digit bore code that equals the bore in millimetres: a 608 has an 8 mm bore, a 625 a 5 mm bore.
The 60x, 62x and 63x series follow the same light-to-heavy logic as larger bearings. The 68x and 69x series are thin-section miniatures; they are normally sold shielded (ZZ) or sealed (2RS), and those versions are slightly wider than open ones.
| Property | |
|---|---|
| Loads | Radial and light axial in both directions |
| Typical uses | Skateboards and scooters, 3D printers and CNC, Fans and small motors, RC models and instruments |
| Standard sizes listed | 33 |
| Dimension standard | ISO 15 |
Dimension series 10
60x miniature series
Includes the 608, the most common skateboard and 3D-printer bearing.
Dimension series 02
62x miniature series
Light miniature series — 625 and 626 are common in 3D printers and RC models.
Dimension series 03
63x miniature series
Medium miniature series with larger section.
Dimension series 18
68x thin miniature series
Widths shown are shielded/sealed widths (ZZ, 2RS); open versions are narrower.
Dimension series 19
69x thin miniature series
Widths shown are shielded/sealed widths (ZZ, 2RS); open versions can be narrower.
Other types
Browse other bearing types
Deep groove ball bearings
The most common rolling bearing: one row of balls running in deep raceway grooves, available open, shielded or sealed.
Size tablesSelf-aligning ball bearings
Two rows of balls with a common spherical outer raceway, tolerating shaft misalignment and deflection.
Size tablesAngular contact ball bearings
Raceways offset so that loads are carried at a contact angle, supporting combined radial and axial loads in one direction.
Size tablesCylindrical roller bearings
Cylindrical rollers with line contact for high radial load capacity; ring flanges determine axial guidance.
Size tablesSpherical roller bearings
Two rows of barrel-shaped rollers with a spherical outer raceway: heavy loads plus misalignment tolerance.
Size tablesTapered roller bearings
Tapered rollers between a cone and a cup carry heavy combined radial and axial loads — the wheel-hub and gearbox workhorse.
Size tablesThrust ball bearings
Shaft washer, housing washer and a ball-and-cage assembly for purely axial loads in one direction.
Size tablesPillow block bearing units
UCP two-bolt pillow block units: a set-screw insert bearing (UC2xx) in a cast-iron P2xx housing, ready to bolt to a frame.
Size tables
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