Technology Explained in a Nutshell The Development of the Rolling Bearing

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FAULHABER Drive Systems

In our series “Technology Explained in a Nutshell,” we regularly showcase masterpieces of engineering and special innovations. Today: the rolling bearing—an unassuming machine component without which modern mechanical and plant engineering would be virtually unthinkable.

Rolling bearings support rotating shafts, transmit forces between the shaft and the housing, and reduce friction in the process. They are found in many machines and systems, such as electric motors, gearboxes, and pumps. The history of rolling bearings ranges from simple wooden rollers to high-precision, sensor-monitored components for automated machines.

From Rolling Under Load to Roller Bearings

The basic principle is simple: A load is easier to move when it does not slide across a surface but rolls on rollers or balls. Even the builders of antiquity used logs to transport heavy stones and building components. 

An early precursor to a ball bearing was found in a Roman shipwreck in Lake Nemis, Italy. A wooden structure containing balls likely enabled a platform to rotate. 

Leonardo da Vinci also studied friction in the 15th and 16th centuries. His notes contain sketches of balls moving along raceways, as well as early concepts for a cage that separates the rolling elements from one another. At that time, the balls were made of wood and, by today’s standards, were not particularly durable. Nevertheless, the concept of roller bearings became established in industry by the end of the 16th century. Gradually, the technology was further developed, and new areas of application were explored. Important areas of application during this period included wagons, carriages, and mills. 

The First Patented Ball Bearing

Welsh ironworker Philip Vaughan took an important step forward. In 1794, he was granted British Patent No. 2006 for an improved bearing system for wagon axles. In his design, iron balls rolled in grooves between the axle and the bearing housing. 

The cast-iron balls were significantly more durable than wooden balls, but they still lacked precision. A modern ball cage was not yet available either. The balls could touch one another and shift their position within the bearing. At that time, the ability to produce large numbers of balls with identical diameters and high roundness was lacking, which hindered reliable mass production.

Friedrich Fischer Shapes the Ball

In 1883, Friedrich Fischer, an engineer from Schweinfurt (Germany), made a significant breakthrough. He developed the so-called ball mill, which made it possible to grind hardened steel balls cost-effectively and bring them to uniform dimensions.

This development fundamentally changed bearing technology. This is because a rolling bearing functions reliably only when the rolling elements are nearly the same size. Even slight dimensional deviations lead to uneven load distribution. Individual balls are then overloaded, while others bear hardly any load.

Fischer's ball-grinding machine paved the way for industrial production. His company gave rise to the bearing manufacturer FAG, which was later acquired by Schaeffler. The precision steel balls were initially used in bicycles, other vehicles, and machinery. As bicycles, railroads, automobiles, and electric drives became more widespread, the demand for high-performance bearings grew rapidly. 

Additional patents from the following years demonstrate the need for low-friction motion and the progress of the technology. In 1898, for example, Henry Timken filed a patent in the United States for the tapered roller bearing. A year later, he founded the Timken Roller Bearing Company (now the Timken Company).

The Breakthrough with the Pendulum Ball Bearing

A fundamental problem with early rigid roller bearings was misalignment. Manufacturing and assembly tolerances meant that, in practice, the shaft, bearing, and housing were not always precisely aligned. In addition, shafts can flex under load. A rigid bearing then tilts. The load is no longer distributed evenly across the rolling elements, and service life is reduced.

Swedish engineer Sven Wingquist developed a solution for this: In 1907, he filed a patent application for a double-row self-aligning ball bearing. The outer raceway for the two rows of balls is designed as a hollow sphere. It can compensate for limited misalignment between the shaft and the housing. As a result, it is less sensitive to misalignment caused, for example, by shaft deflection.

That same year, Svenska Kullagerfabriken—SKF for short—was founded in Gothenburg. Wingquist’s pendulum ball bearings brought the company international recognition. They were particularly important for textile machinery, where long shafts and large distances between bearings often led to misalignment.

This design marked a turning point in the history of the roller bearing: what had been a delicate precision part became a robust machine component that operates reliably even under adverse installation conditions. At the beginning of the 20th century, a number of roller bearing manufacturers were founded. The precision components they produced quickly spread worldwide.

A Variety of Rolling Bearing Designs Emerges

Over time, a wide variety of rolling bearing designs have emerged. The most noticeable—but by no means the only—difference lies in the rolling elements: balls have only a small contact area with the raceway. This reduces friction and enables high rotational speeds. Rollers, on the other hand, have a larger contact area. They can therefore withstand higher radial forces. Depending on their shape, they are classified as cylindrical, spherical, tapered, self-aligning, needle, or toroidal rollers. The choice of design depends, among other things, on radial and axial forces, the direction of the load, rotational speed, installation space, stiffness, lubrication, and environmental conditions, for example: 

• Deep-groove ball bearings are versatile bearings that primarily support radial forces and limited axial forces and are suitable for high rotational speeds.
• Angular contact ball bearings transmit combined radial and axial forces. Multiple bearings can be arranged in pairs to increase axial stiffness.
• Cylindrical roller bearings offer high radial load capacity. Depending on the design, they may also accommodate axial displacement of the shaft.
• Tapered roller bearings transmit both radial and axial forces. They are used, among other applications, in vehicle wheel bearings and transmissions.
• Needle roller bearings use particularly slender rollers. They achieve a high load-carrying capacity with a low radial height.
• Self-aligning roller bearings are designed for high loads and compensate for minor misalignments, similar to self-aligning ball bearings.
• Erich Franke developed wire roller bearings based on the design principle of cross-roller bearings. The rolling elements run on wires embedded in the surrounding structure. This enables particularly space-saving rotary joints. 

New Materials for Rolling Bearings

Modern rolling bearings are primarily made of high-purity, hardened chrome or case-hardened steels. Heat treatments improve hardness, toughness, and fatigue strength. For special applications, there are rolling bearings made partly or entirely of ceramic, glass, stainless steel, or plastic. 

Insulating layers on the rings reduce damage caused by the flow of current, such as when used in frequency converters. Hybrid bearings go one step further: Their rings are made of steel, but the rolling elements are made of insulating ceramic, typically silicon nitride or zirconia. Ceramic balls offer additional advantages: they are lighter and more durable than steel balls. However, because they are more difficult to machine, these roller bearings also come at a slightly higher price.

The Rolling Bearing Is Becoming Smart

For a long time, rolling bearings did not provide any data on their condition. The first sensor bearings appeared in the late 1980s. Initially, they were used for ABS systems in the automotive sector and for rail vehicles. Later, sensor bearings were introduced for condition monitoring of industrial machinery. They typically measure temperature and vibrations. From these signals, characteristic fault frequencies can be derived that indicate wear. 

In conjunction with system control and data analysis, this enables condition-based maintenance: A bearing is no longer replaced at fixed intervals; instead, maintenance is performed when measurement data actually indicates the onset of damage. This practice reduces unplanned downtime and prevents the replacement of components that are still functional. Such monitoring systems are already available for rail vehicles, for example.

From a Simple Machine Element to a System Component

Today, rolling bearings play a key role in determining the efficiency, noise levels, precision, and service life of many machines. That is why researchers and industry continue to work on making these components more efficient and sustainable. What began with wooden rollers and balls to reduce friction has evolved into precision components for networked machines and systems.

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