A ball bearing is a rolling bearing in which balls roll as rolling elements between the inner ring and the outer ring. The point contact between ball and raceway creates very low friction, allows high rotational speeds and enables the bearing to carry both radial and axial loads. Ball bearings are the most widely used type of rolling bearing worldwide – from household appliances to high precision machine tools.
But not every ball bearing is the same: between a standardised mass product from a catalogue and a precision ball bearing that acts as a key component in a machine, there are worlds of difference – in tolerance, material, geometry and function. Franke develops and manufactures ball bearings exclusively for the second case: as high quality precision components in mechanical engineering.
Design and function of a ball bearing
A ball bearing consists of four basic components: the inner ring, which rotates with the shaft, the outer ring, which is fixed in the housing, the balls as rolling elements and the cage, which keeps the balls evenly spaced. The balls roll on annular raceways (grooves) in the inner and outer ring. The point contact keeps friction to a minimum – at the cost of a lower radial load capacity compared with a roller bearing.
Overview of ball bearing types
Deep groove ball bearing
The most universal ball bearing: deep grooves in the inner and outer ring allow radial and axial loads to be carried in both directions. High rotational speeds, low maintenance, wide range of applications. The standard in mechanical engineering – standardised according to DIN 625 / ISO 15.
Angular contact ball bearing
The inner and outer ring are offset from each other, so that loads are transmitted at a defined contact angle (15°, 25° or 40°). Ideal for high axial loads in one direction – usually installed in pairs. Typical applications: machine tool spindles, pumps, compressors.
Four point contact ball bearing
Each ball contacts both raceway rings at four points. This allows high axial loads in both directions as well as moment loads to be carried – in a compact single row design. Particularly suitable for slewing rings and rotary tables.
Self-aligning ball bearing
The outer ring has a spherical raceway that tolerates misalignment and shaft deflection of up to several degrees. Used in agricultural machinery, conveyor technology and wherever shafts cannot be exactly aligned.
Slim bearing
Extremely thin wall thickness with a relatively large diameter. Slim bearings save installation space and weight in compact designs – for example in robot joints, medical devices or camera platforms. Franke offers slim bearings as type LSA.
Standard ball bearing vs. precision ball bearing: the key distinction
The term "ball bearing" covers an enormous range – from standard parts produced by the million for household appliances and vehicles to high precision custom designs for medical technology or aviation. For mechanical engineers and designers, this distinction is decisive:
| Feature | Standard ball bearing (mass product) | Precision / customised ball bearing |
|---|---|---|
| Tolerance | Normal class | Tighter tolerances depending on the application |
| Geometry | standardised (DIN/ISO) | adapted to the design |
| Material | standard steel | corrosion resistant steel, aluminium, bronze, plastic, carbon |
| Bearing ring | separate component | can be integrated into housing / shaft |
| Typical application | electric motors, household appliances, vehicles | mechanical engineering, robotics, medical technology |
| Procurement | catalogue product, available immediately | project based, advice intensive |
Franke serves exclusively the field of precision and customised ball bearings. Standard ball bearings as mass products are not part of the portfolio – the focus is on bearing arrangements in which installation space, weight, material or integration place special demands.
The Franke wire race bearing principle: ball bearings rethought
The most consistent form of customisation is the Franke wire race bearing principle: instead of separate bearing rings, steel wires are inserted into slots in the housing or shaft. The balls run directly on these wires – the inner or outer ring is completely eliminated as a separate component.
The result: the bearing becomes part of the design. This saves installation space, weight and number of parts. At the same time, geometry, material and specifications can be freely adapted to the respective application.
Typical Franke ball bearing product lines:
- Type LEL – ball bearing with ground raceways for maximum smooth running and precision, diameter 70 to 150 mm
- Type LER – economical ball bearing with profiled raceways for medium rotational speeds and accuracies, diameter 40 to 150 mm
- Type LSA – slim bearing with thin wall thickness for confined installation spaces, inner diameter 3 to 15 inches
- Type LVA/LVB – ready to install slewing rings in steel, diameter 100 to 1,800 mm
Applications of precision ball bearings
- Medical technology – computer tomograph, C-arm X-ray device, surgical microscope
- Robotics & automation – articulated robot, tool changer, swivel station in a placement machine
- Intralogistics – steering gear for automated guided vehicles (AGV)
- Aviation & antenna technology – antenna bearings, laser optics on aircraft, satellite antennas
- Mechanical engineering – circular knitting machine, beverage filling, packaging machines
- Camera technology – camera crane, aerial camera
Frequently asked questions about ball bearings
What is a ball bearing?
A ball bearing is a rolling bearing in which balls roll as rolling elements between the inner ring and the outer ring. The point contact between ball and raceway creates very low friction and allows high speeds. Ball bearings can carry both radial and axial loads and are the most widely used bearing type in mechanical engineering.
What is the difference between standard ball bearings and precision ball bearings?
Standard ball bearings (e.g. according to DIN 625) are standardised mass products for general applications. Precision ball bearings are manufactured with tighter tolerances and are used in demanding applications such as machine tools, medical technology or measuring technology. In addition, there are customised ball bearings such as the Franke wire race bearing principle, in which the bearing rings are integrated directly into the customer’s design.
What types of ball bearings are there?
The most important ball bearing types are: deep groove ball bearings (universal, radial and axial loads), angular contact ball bearings (high axial loads in one direction), four point contact ball bearings (axial loads in both directions), self-aligning ball bearings and slim bearings for confined installation spaces. For customised bearings, Franke offers wire race bearings with balls as a ball bearing variant.
When is a customised ball bearing worthwhile instead of a standard bearing?
A customised ball bearing is worthwhile when standard bearings force design compromises: in confined installation spaces, with unusual geometries, special materials (e.g. corrosion resistant, non-magnetic) or when the bearing ring is to be integrated directly into a housing component. This saves weight, reduces the number of parts and can lower the overall cost of the design.
What is a wire race bearing with balls?
A wire race bearing with balls is a special form of ball bearing in which solid raceways are replaced by inserted steel wires. The balls run directly on these wires. The wires are inserted into grooves in the housing or shaft, so the bearing ring is no longer a separate component. The principle was developed by Franke and allows maximum design freedom with minimal installation space and weight.
Further terms in the Franke glossary: Rolling bearing | Roller bearing | Slewing ring | Individual bearings