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This article will take an in-depth look at ball bearings.
The article will take a look at topics such as:
This chapter will discuss the ball bearings’ design, construction, and their function.
Ball bearings are types of rolling-elements bearings that carry loads, reduce friction, and position moving machine parts while facilitating motion.
They reduce surface contact and friction across moving planes by using separate two "races," or bearing rings. Compared to flat surfaces that rub against each other, the coefficient of friction is reduced by the rotating motion of the balls.
Ball bearings consist of four major parts which are: 2 rings/races, the balls (the rolling elements), and the retainer (the ball separator). Angular contact ball bearings and radial ball bearings include an inner and outer ring. Angular contact ball bearings and radial ball bearings are designed to support loads that are oriented in a perpendicular direction to the axis of rotation, known as radial loads.
The outer race is stationary and mounts into housing. When the radial load is transferred from the bearing to the housing, the outer race also aids in that transfer. The inner race supports and guides the shaft during rotation, and it mounts onto a rotating shaft. The function of the rolling elements is for carrying the load and distribution of the load throughout the raceways.
The rolling elements rotate at a different speed from the speed of the inner race, but they rotate around the inner race. The separator functions as a barrier that prevents the balls from bumping into each other. The separator is situated between the balls. Thrust bearings support loads that are parallel to the axis of rotation, which are referred to as axial loads. Thrust ball bearings consist of two rings of equal size.
The material used to make rolling bearing ball bearing balls vary widely and is always mainly focused on the ring’s materials. This gives assurance of the harmonization of the interplay of cage, outer ring, and inner ring in the system. This is usually important when heating or cooling of the bearings is involved in the application. The ball bearing running properties are of importance; they must be good. The most common materials used to make ball bearings are listed below, with their relation to the ring material:
This material is used for metal ball bearings. For these types of ball bearings, balls made from hardened steel are often used. The material that is often used is chrome steel having a composition of about 1% carbon and 1.5% chrome.
Martensitic chrome steel balls’ properties make them suitable for the production of ball bearings since they make stable components that are resistant and durable in continuous operation. Balls that are made from roller bearing steel are durable and robust. They are not highly susceptible to corrosion, and needle rollers and cylindrical rollers are made of this material.
This material is used for ball bearings made of plastic. These stainless steel balls are not hardened. They exceptionally resist corrosion and also resist saltwater and alkalis. Hardened steel balls must not be used for plastic ball bearings. The limits of the material in the plastic ring limit the maximum permissible load for the plastic ball bearings. Stainless steel balls are cheaper than glass balls.
When a metal free ball bearing is needed, this is when glass balls come into play. Glass balls are also used when the ball bearings’ chemical resistance is high. Soda-lime glass is used to make bottles, flat glass, drinking glasses, and ball bearing material. The chemical properties of soda-lime glass are very good and suitable for ball bearings usually exposed to chemical stress for a short time, but not to great chemical stress. The name lemon glass has also been given to it because of its light green color.
This type of glass is much more expensive compared to soda-lime glass. The chemical-resistance properties of borosilicate are even greater than those of soda-lime glass, which means that it is utilized in applications that involve strong acids. The benefits of borosilicate glass are listed below:
This type of material is used for balls for ceramic ball bearings. Ceramic balls made from aluminum oxide are also called oxide ceramics. They have a polycrystalline structure. These balls are light weight and have the following properties: good resistance to corrosion, good abrasion resistance, and good heat resistance.
They are extremely resistant to corrosion, despite other influences like water, acids, and salt solutions. It is important that these types of balls don’t have contact with hydrochloric acid, hydrofluoric acid, strong alkaline solutions, and warm sulphuric acid. These types of balls are also known to be self-lubricating and they are electrically insulating. Balls made of aluminum oxide are colored in white to ivory and are manufactured according to ASTM F 2094 Class II/III.
Balls made from silicon nitride ceramic material have a light weight, but also have the properties of great toughness and corrosion resistance that is outstanding. But they can be corroded by certain acids and base solutions. The material exhibits an insulating effect. The balls made from this material are self-lubricating and their resistance to temperature fluctuations is great, which noticeably affects the bottom line. These types of balls are much more expensive than balls made from aluminum oxide. The color of silicon nitride balls is black mother-of-pearl color.
The critical specifications of ball bearings are dimensions and operating specifications. These will be discussed below.
The following are important dimensions to consider when specifying ball bearings:
A standard number system is used by the bearing industry, for bearings having metric diameter bores. To obtain the bore in millimeters, multiply bore sizes that are 04 and up by 5. If the bore is a hex, this will be referring to the dimension across the flats. If the ball is tapered, this will be referring to the smaller diameter.
If a housed unit, the outside diameter of a ball bearing does include the housing but doesn’t include the flange if a flanged bearing. The overall width of the outside of the bearing is the outer ring width.
The locking collar, if present, is part of the overall width of the bearing assembly.
An optimum bearing life is obtained when the balls and raceways have a contact surface that is minimal and supplemented with proper lubrication. Loads for ball bearings are subject to dynamic or static loads, and radial or axial loads. This means that there must be an account for four variables in order to determine working loads for a bearing.
Ball bearings can handle substantially more dynamic and radial loads than static and axial loads. Flattened spots on the balls will be the first sign of non-elastic deformation. They will hinder the rotation. The operating speeds, load, and environmental factors determine the calculated life of a bearing. Under the requirements of industry standards, typically 90% of bearings can still be serviced after a million rotations. This is what is termed as bearing fatigue.
Ball bearings reduce rotational friction and support axial and radial loads. They can achieve this by utilizing at least two races to contain the balls and by transmitting the loads through the balls. In many applications, one race is attached to the rotating assembly (e.g. a shaft or hub), and the other race is stationary.
During the rotation of one of the bearing races, the balls also rotate as a result of the rotation of the bearing races. The balls have a much lower coefficient of friction because they are rolling, than if there were two flat surfaces sliding against each other. The load capacity of the ball bearings tends to be lower for their size than other types of rolling-element bearings because of the smaller area of contact between the races and the balls. However, they can tolerate some misalignment of both the inner and outer races.
This chapter will discuss the various types of ball bearings.
These types of bearings have raceways of both inner and outer rings that are displaced relative to one another in the bearing axis direction. This means that these types of bearings are designed in such a way that they can accommodate combined loads (simultaneously acting axial and radial loads). These types of bearings are available in different design styles, with shielding or seals.
These do not only prevent contamination but also act as retainers for lubricants. These bearings are made from the following materials: ceramic hybrid materials, stainless steel, cadmium, or plastic, and maybe plated with chrome, or other materials. They can also be re-lubricated, pre-lubricated, or can feature solid lubrication. Angular contact bearings are classified further into the following subtypes:
These types of bearings incorporate a high number of balls to provide a relatively high load carrying capacity, and they can accommodate axial loads in a single direction only. They are typically adjusted against a second bearing, and consist of non-separable rings.
These bearings have a design that corresponds to two single row bearings arranged back-to-back, but where two single bearings take too much axial space. They can accommodate axial and radial loads in either direction and tilting moments.
These types of bearings have a design that allows them to support axial loads in all directions and their carrying capacity is high. They can support a radial load that is limited for a given axial load, they are separable, and use limited axial space than double row bearings.
These types of bearings are the most commonly used types of ball bearings. They are available in the shield, seal, and snap-ring arrangements. The dimensions of the race within these kinds of bearings closely match the dimensions of the contained ball. They also have the ability to support heavy loads. Deep groove bearings offer both axial and radial support.
However, the relative levels of such loads can’t be varied because the contact angle can’t be adjusted. Deep groove ball bearings are classified further into the following classes:
These are the most common types of all bearings. They are widely used. There are circular arcs of a radius that is slightly larger than that of the balls on the raceway grooves of the inner and outer rings. To add on top of radial loads, the imposition of axial loads can be done in either direction. These types of ball bearings have a low torque, and are highly suited for applications in which high speeds and low power loss are required. To add on top of open type bearings, these bearings often have shields made of steel or installed rubber seals on one side or both sides and are pre-lubricated with grease.
These types of ball bearings have a design that corresponds to single row deep groove ball bearings. They have raceway grooves that are deep and uninterrupted and have a close osculation with the balls. This enables the bearings to accommodate axial and radial loads in both directions.
Double row deep groove ball bearings perfectly fit bearing arrangements in which there is an inadequate load-carrying capacity of a single row. Double row deep groove bearings are slightly wider compared to single row bearings in the 63 and 62 series, for the same bore and outside diameter. But they have a load-carrying capacity that is considerably high. These types of ball bearings are only found as open bearings (without any seals or shields).
These types of ball bearings are formed by a combination of two angular contact bearings. The combinations that are possible include back-to-back (type DB), face-to-face (type DF) with the faces of the outer ring together, or both front faces being in the same direction (type DT).
DB and DF duplex bearings are able to take axial and radial loads in either direction. When an axial load is strong, and in one direction and the imposition of the load equally on each bearing is necessary, type DT is used.
Ceramic bearing balls can have a weight of up to 40% less than steel ones, depending on the material and size. This results in the reduction of the centrifugal loading and skidding, so hybrid ceramic ball bearings can operate 20% to 40% faster than conventional bearings. The meaning of this is that, the force exerted inwards against the ball during the spinning of the bearing, by the outer race groove is less.
This reduction in force will reduce the friction as well as the rolling resistance. The bearing is allowed to spin faster by the lighter balls, and the bearing uses less power to maintain its speed. The ceramic balls are harder as compared to the race. Ceramic hybrid ball bearings are constructed with inner and outer steel rings and ceramic is stronger than steel. But it is also stiffer, resulting in increased stresses on the rings, and hence the load capacity is decreased.
These are small bearings having balls as their rolling element. Miniature bearings are sometimes referred to as micro bearings or instrument bearings with inner and outer rings, snap rings, balls, and retainers. These types of bearings are utilized in industrial and medical handpieces and other precision applications. Ball bearing designs include angular, radial, thrust, and pivot.
Miniature bearings are manufactured under the standard European metric sizes under 20 millimeters. They vary from one eighth of an inch in their overall diameter to 20 millimeters in their overall size. One of the smallest sizes is a bore of 0.04 and an overall size of one eighth of an inch. Because of its unique size, this type of bearing is helpful in a broad range of applications.
Miniature bearings are designed to achieve high performance that is reliable for moderate thrust and radial loads at low operating torque. Therefore the attributes that are most important with miniature bearings are accuracy, speed, and longevity. To add on top, the silence of a bearing running at high speeds can also be of vital importance. Miniature bearings are not used in applications involving high loads, and due to the small amount of material used, stainless steel is used to produce many of the bearings.
These types of bearings allow for extra fine precision and tolerance. Precision ball bearings are ideal for applications having stringent requirements for speed and guidance accuracy. Precision ball bearings are available in two main types which are angular contact bearings and deep groove bearings. Deep groove ball bearings have full shoulders on either side of the raceways of the inner and outer ring, allowing for the addition of seals or shields with ease.
These bearings are capable of handling thrust loads, radial loads, or a combination of both. They are available in multiple sizes that include miniature precision bearings, and are available with various types of cages. Deep groove bearings are extremely versatile and are found among the most widely used bearing types.
Angular contact bearings are composed of one complete ring shoulder; the other ring is not present because it is partially or totally removed. This in turn will allow them to have a larger ball, which provides greater load capacity and speed capability. There are also various cage designs that are available to meet specific high-speed requirements.
Angular contact bearings can support thrust loads or a combination of both radial and thrust loads, but they are not capable of supporting radial loads on their own. Angular contact bearings can support thrust loads in both directions when implemented face-to-face or back-to-back.
Miniature ball bearings are highly engineered components that lower friction and enhance the operational life of the equipment. If attention is not paid to these small sized bearings, maintenance and flexibility can become challenges.
The bearings must be maintained on a regular basis, so that they can maintain a smooth operation with a long life. The bearings must be lubricated regularly. The options for these small bearings can be hard to find, making it challenging to complete a working project. To eliminate these challenges, work with a supplier that has the options you need.
Rolling bearings guide and support rotating machine elements that include axles or wheels, shafts and transfer loads between the components of the machine.
They offer high precision and low friction and therefore their rotational speeds are high and the noise, energy consumption, heat, and wear is reduced. These types of bearings are cost effective. They are exchangeable machine elements that typically fall under national or international dimension standards.
These types of ball bearings consist of two rows of balls, a raceway that is commonly sphered in the outer ring and two raceway grooves that are deep and uninterrupted, in the inner ring.
They are available sealed or open. These types of ball bearings are not sensitive to angular misalignment of the shaft in relation to the housing, which can be caused, for instance by the deflection of the shaft.
These types of ball bearings are amazingly versatile. They can be utilized in a wide range of applications including arts and crafts to use for bikes, precision instruments, model engineering and many experiments and projects.
There are many different types of bearings made from stainless steel available. There are ball bearings made from hardened steel for hobby projects or professional work requirements. Steel ball bearings are durable and they are resistant to corrosion.
These types of ball bearings are a special type of ball bearings that are designed specifically for axial loads. They are not capable of supporting radial loads at all.
Thrust ball bearings have properties of smooth operation, low noise, and are capable of applications that involve high speeds. They are available in two variations which are single direction and double direction bearings and the opting depends on whether the load is bidirectional or unidirectional.
These types of ball bearings are composed of bearing rings that are washer-like, and have raceway grooves. The ring that is attached to the shaft is known as the shaft washer or inner ring, while that attached to the housing is termed the housing washer or outer ring.
These types of ball bearings are composed of three rings with a center ring being fixed to the shaft. Some thrust ball bearing with an aligning seat washer beneath the housing washer is available. To compensate for mounting error or shaft misalignment, the seat washer is fixed beneath the housing washer. In smaller bearings, pressed steel cages are usually used, while in larger ones, machined cages are used.
This chapter will detail the applications and benefits of using ball bearings.
There are many special applications for bearings that include aerospace, automotive, agriculture, ball screw support, medical or dental, instrument or miniature, pump, military, sporting, spindle or super precision, consumer goods and aircraft or airframe control.
Airframe and aircraft control bearings are designed in a special way to meet the demands of aerospace applications and aircraft control. They can be of different types including roller, ball, or needle roller construction.
There are ball bearings that are designed for aerospace applications that include jet engines and helicopters.
There are also ball bearings designed for agriculture equipment and environments.
These are bearings designed specifically for the automotive industry.
These ball bearings are designed specifically for use in applications that involve lead screw or ball screw. Most of the ball bearings that are ball screw support are angular contact ball bearings with an angle of contact that is steep, such as 60 degrees, and are found in duplex, triplex, as well as quadruplex configurations. The other designs that are available are bearings that contain separate radial and thrust roller bearings in a single assembly. There are also cartridge designs that are available that include a seal, housing, and bearings.
Miniature or instrument ball bearings are small angular contact or deep groove bearings. They are utilized in applications that require very small bearings like a computer disk drive and dental drills.
There are ball bearings that are designed specifically for dental or medical equipment like miniature ball bearings.
These are ball bearings designed for the conditions that are found in pumps that include poor or degraded lubrication, high loads, and high operating temperatures.
There are ball bearings with high precision intended for use in machine tool spindles.
There are ball bearings that are designed specifically for the consumer goods market and the sporting market. Products in the category include skateboards, inline skates, and fishing reels.
Ball bearings are rolling elements that facilitate motion while reducing friction in moving machine parts. There are different materials that are used to produce ball bearings including steel, plastic, ceramics, etc. each type of material exhibits its own properties which makes it unique. There are also many different types of ball bearings including angular contact ball bearings, steel made ball bearings, deep groove ball bearings, and some are further classified into subgroups, with each subgroup having differences from the other one.
Each ball bearing has its own specific type of application depending on its material, load-carrying capacity, size, or design. Therefore when selecting a ball bearing, one must take into consideration the type of material used to produce the ball bearing, the size of the ball bearing, the design of the ball bearing, the load-carrying capacity of the ball bearing. The ball bearing must suit its application depending on the mentioned parameters.