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When a seized bearing brings a 3D printer, RC car, or small motor to a grinding halt, finding the right miniature replacement fast is critical. These 624–629 series miniature deep groove ball bearings are designed for makers, hobbyists, engineers, and repair technicians who need a dependable drop-in solution across a wide range of compact rotating assemblies.
Available in two seal types — 2RS (double rubber contact seal) and ZZ (double metal shield) — these bearings are manufactured from GCR15 bearing steel (equivalent to AISI 52100 chrome steel) with a precision-ground raceway. Bore diameters range from 4 mm to 9 mm (approx. 5/32" to 23/64"), with outer diameters from 13 mm to 26 mm and widths of 5 mm to 8 mm, covering the full 624 / 625 / 626 / 627 / 628 / 629 designation range.
Typical applications include miniature deep groove ball bearing replacement for 3D printers (idler pulleys, extruder arms), RC vehicle wheel hubs and steering pivots, small electric motor shaft support, inline skate wheels, fidget spinners, and light-duty conveyor rollers — anywhere a compact, low-friction rotating support is needed.
| Bearing Series | 624 / 625 / 626 / 627 / 628 / 629 |
|---|---|
| Seal Type | 2RS (rubber contact seal) or ZZ (metal shield) |
| Material | GCR15 chrome bearing steel (AISI 52100 equivalent) |
| Bore Diameter (ID) | 4 mm / 5 mm / 6 mm / 7 mm / 8 mm / 9 mm |
| Outer Diameter (OD) | 13 mm / 16 mm / 19 mm / 22 mm / 24 mm / 26 mm |
| Width | 5 mm / 5 mm / 6 mm / 7 mm / 8 mm / 8 mm |
| Lubrication | Factory-greased (2RS) / Unlubricated or lightly oiled (ZZ) |
| Sealing (both sides) | Yes |
| Load Type Supported | Radial + moderate axial |
| Pack Quantity Options | 1 pcs / 4 pcs / 10 pcs / 20 pcs |
| Operating Temperature | See variant options |
| Tolerance Class | See variant options |
2RS bearings have rubber contact seals on both sides that physically touch the inner ring, providing better exclusion of dust, dirt, and light moisture — ideal for 3D printers, outdoor RC vehicles, and dusty workshop environments. ZZ bearings use non-contact metal shields that leave a small gap, resulting in lower friction and drag, making them better suited for higher-speed, dry applications such as small electric motors and fans. If in doubt, 2RS is the more protective choice for general DIY use.
Match the bearing designation to your application's bore (inner diameter), outer diameter, and width. The variant names include all three dimensions — for example, 625-2RS 5×16×5mm means 5 mm bore, 16 mm OD, 5 mm wide. Measure your existing bearing or bearing seat with calipers before ordering. The 624 series (4 mm bore) is common in 3D printer idler pulleys; the 626–629 range suits slightly larger motors and wheel hubs.
GCR15 chrome steel is the standard material for precision ball bearings worldwide, offering a typical hardness of 60–64 HRC and good fatigue life under cyclic radial loads. These miniature bearings are well-suited for light-to-moderate radial loads in compact mechanisms. They are not intended for heavy industrial machinery, high-impact loads, or continuous operation at elevated temperatures. For specific dynamic load ratings, refer to the bearing designation in a standard bearing catalog (e.g., SKF, NSK equivalent data for 62x series).
GCR15 chrome steel provides moderate corrosion resistance suitable for indoor and dry outdoor use. The 2RS rubber seals help keep moisture out of the raceway. However, these are not stainless steel bearings — for applications with continuous water exposure, salt spray, or aggressive chemicals, consider stainless steel (AISI 440C) alternatives. For typical DIY, hobby, and light-industrial use in normal environments, these bearings perform reliably.
Yes, provided the bore, outer diameter, and width match your OEM specification. The 624 and 625 sizes are among the most common bearings used in FDM 3D printer idler pulleys (often pressed into GT2 pulley bores), and the 626–629 range covers many RC car wheel hubs and steering knuckles. Always verify dimensions with calipers before installation. These bearings conform to standard ISO dimensional tolerances for interchangeability.
If you need a single emergency replacement, the 1-piece option gets you back up and running quickly. However, bearings in high-cycle applications (3D printer idlers, RC drivetrains) tend to wear in sets — buying a 4, 10, or 20-piece pack means you have spares on hand for the next service interval and typically lowers the per-unit cost. For workshop stock or ongoing builds, the 10 or 20-piece packs offer the best value per bearing.
The 2RS variants are factory-greased — the rubber seals retain the grease inside the raceway for the bearing's service life. The ZZ metal-shield variants may have a light oil film applied at the factory; for higher-speed or precision applications, you can add a small amount of appropriate bearing oil through the shield gap. Do not over-lubricate, as excess grease increases drag and heat.
