A roller bearing lets a shaft spin on a ring of rollers instead of a sliding surface. Use the view to look inside and identify each ring, then see how the load passes from the turning shaft out to the fixed housing.
A roller bearing is a round assembly that supports a turning shaft while letting it spin with very little friction. It is built from two hardened rings and a set of rollers between them, all held together by a cage. Instead of the shaft rubbing on its support, the rollers roll, so almost nothing is worn away.
From outside it is just a smooth metal ring. Everything that makes it work — the two raceways, the rollers and the cage — is hidden inside the metal, so a cross-section is the only way to see how the parts are arranged and how the load is carried.
The shaft is the part the bearing exists to support. It spins continuously, and without the bearing it would have to rub directly against the machine frame.
The inner ring is fitted tightly onto the shaft, so it turns at the same speed. Its hardened outer face forms one of the two smooth tracks, called raceways.
A ring of rollers sits in the gap between the two rings. As the shaft turns, each roller rolls along the raceways and carries the load, so the parts glide past each other instead of scraping.
The cage is a thin ring with pockets that hold every roller at an even spacing. It stops the rollers from crowding into one spot, rubbing together and jamming.
The outer ring stays still, held in the housing. The rollers pass the load from the turning inner ring out to this fixed ring, and from there into the machine frame.
Sliding surfaces rub, so they heat up and wear. Rollers roll, and rolling has far less friction than sliding, so a roller bearing turns a heavy shaft more freely and lasts much longer.
The cage keeps every roller evenly spaced around the ring. Without it the rollers would bunch together, rub against each other and jam, so the cage simply guides them at an even pitch.
Normally the shaft and the inner ring turn, while the outer ring is fixed in the housing. The rollers roll between the two, carrying the load from the turning side to the fixed side.
A roller meets the raceway along a line instead of a single point, so it spreads the same load over more metal. That lets it carry heavier loads than a ball of the same size.
Yes. A thin film of oil or grease keeps the rollers, cage and raceways apart so they never touch metal-to-metal, which is what keeps friction and wear low.