634 bearing
The 634 is a miniature ball bearing with a 4 mm bore, 16 mm outside diameter and 5 mm width, open (no seals or shields).
Size & specs
| Type | Miniature ball bearing |
|---|---|
| Bore (ID) | 4 mm (0.157 in) |
| Outside diameter (OD) | 16 mm (0.63 in) |
| Width | 5 mm (0.197 in) |
| Seals / shields | Open |
Cross reference: same bearing, other brands
| SKF | 634 |
|---|---|
| NTN | 634 |
| NSK | 634 |
| FAG | 634 |
| Timken | 634 |
| Koyo | 634 |
Budget brands usually sell this as 634. Add C3 if your old bearing was stamped C3 (looser fit for hot-running motors).
Where to buy
Other bearings with a 4 mm bore
Questions
What size is a 634 bearing?
4 × 16 × 5 mm (bore × outside diameter × width).
What is an open 634 bearing?
It has no seals or shields, so it must be lubricated by the machine (oil bath or grease). Choose 2RS or ZZ if the bearing needs to stay clean on its own.