Bearing Basics: What Bearings Do and How to Use This Site

What does a bearing do?

A bearing supports a rotating shaft and reduces friction between the shaft and its housing. Almost every machine with rotating parts — motors, gearboxes, pumps, wheels, fans — relies on bearings.

A typical rolling bearing has four parts:

• Inner ring — mounted on the shaft, rotates with it
• Outer ring — seated in the housing, usually stationary
• Rolling elements — balls or rollers between the rings
• Cage — keeps the rolling elements evenly spaced

The most common type: deep groove ball bearings

Deep groove ball bearings are the workhorse of the bearing world. They handle radial loads and moderate axial loads in both directions, run at high speed, need little maintenance, and are inexpensive. When someone mentions a bearing number like 6204, it is almost always a deep groove ball bearing.

Understanding a bearing number

A designation like 6204 packs the key facts into a short code:

• The first digit (6) is the bearing type: deep groove ball bearing
• The second digit (2) is the dimension series: light, medium or heavy
• The last two digits (04) give the bore: 04 × 5 = 20 mm

Suffixes add more detail — 2RS means rubber seals on both sides, /C3 means internal clearance greater than normal.

How to use this site

• Know the model? Use the search on the home page or the Find Specs page to see dimensions and load ratings per manufacturer.
• Not sure which bearing you need? Try the Bearing Selection guide — four questions lead you to a recommendation.
• Want to compare brands? Every detail page lists manufacturer data (currently NSK and SKF) side by side, with catalog references.

A word on the numbers

Load ratings differ slightly between manufacturers because each tests and calculates to its own methods. The values on this site always cite the official manufacturer catalog they come from — use them for comparison and preliminary design, and confirm final selections with the manufacturer’s own engineering tools.