What is an adapter bearing (Y-bearings)?

Adapter bearings are used in ball bearing units which consist of a precision wide inner ring bearing assembled into a housing made of cast iron, pressed steel, or rubber. The precision wide inner ring bearings are called y-bearings because their typical locking mechanism, two grub screws 120° apart. The induced direction from this locking forms a Y. Ball bearing units are supplied pre-lubricated and are designed to slip fit onto the shaft. The locking method is either eccentric self-locking or set-screw locking.

SKF
skf.com