What is a Bearing? Construction, Functions and Common Types

A bearing is a precision machine element that allows one part to rotate or move relative to another with as little friction as possible, while carrying load. If a shaft turns, a wheel spins, or a linear slide moves — there is almost certainly a bearing somewhere doing the work.

At SLS Bearings India, we supply bearings from NTN, SKF, FAG, Timken, NSK and Koyo to plants across textile, cement, steel, gearbox, CNC, wind, solar, hydraulic and aviation sectors. This guide is the starting point: what a bearing actually is, how it's built, and which type belongs where.

What does a bearing do?

Every bearing has two jobs:

1. Reduce friction between moving parts so they consume less energy, run cooler and last longer.
2. Support load — either radial (perpendicular to the shaft), axial / thrust (along the shaft), or a combination of both.

Without bearings, shafts would seize, gearboxes would overheat in minutes, and wheels would grind themselves into scrap. Bearings are the reason modern machinery is reliable.

Construction of a typical rolling bearing

Most industrial bearings are rolling-element bearings. They share four core parts:

1. Outer ring (cup) — the stationary race, usually press-fit into a housing.
2. Inner ring (cone) — the rotating race, mounted on the shaft.
3. Rolling elements — balls, cylinders, tapered rollers, spherical rollers or needles that roll between the two rings.
4. Cage (retainer) — a steel, brass or polyamide frame that keeps the rolling elements evenly spaced.

A seal or shield is often added to retain grease and keep contamination out. The contact surfaces are made from hardened chrome steel (100Cr6 / SAE 52100) ground to micron-level tolerances — which is why even a cheap-looking bearing is in fact a high-precision component.

Plain bearings vs rolling bearings

• Rolling-element bearings use balls or rollers — low starting torque, high efficiency, ideal for most rotating machinery.
• Plain bearings (bushes) use a sliding film of oil between two surfaces — quieter, simpler, used in engines, large turbines and some heavy presses.

The rest of this guide focuses on rolling bearings, which make up the bulk of the SLS catalog.

Common bearing types in Indian industry

How to pick the right bearing

For most maintenance and procurement decisions, three questions get you 90% of the way:

1. What kind of load? Radial only, axial only, or both?
2. How fast does it spin? High-speed favours ball bearings; heavy slow loads favour rollers.
3. Is there shaft misalignment or shock? Then look at spherical or self-aligning designs.

From there, the size is fixed by the shaft diameter (bore), housing bore (outer diameter) and width — the three numbers stamped on every bearing.

Sealing, lubrication and life

A correctly chosen bearing will still fail early if it's not protected and lubricated:

• Open bearings rely on the housing for grease and protection.
• ZZ / 2Z shields keep large debris out — used in clean indoor applications.
• 2RS / DDU rubber seals retain grease and block water and dust — preferred for outdoor, wet or dusty plants.
• Most bearings are grease-lubricated for life; high-speed spindles and large industrial bearings use oil bath or oil-mist systems.

Follow the manufacturer's L10 life rating, keep loads within the dynamic capacity (C), and a quality bearing from SKF, NTN, FAG, Timken, NSK or Koyo will routinely outlast the machine around it.

Where to go next

• Browse [bearing types](/bearings) to see series, sizes and applications for each design.
• See the [brands we stock](/brands) and what each is best known for.
• Have a part number in hand? Use the search at the top of the page or [send an RFQ](/rfq) and we'll get back to you the same working day.

Bearings look simple from the outside, but the right one in the right place is what keeps a plant running. If you're unsure which type fits your application, talk to us — that's what we're here for.