The main mechanical bearing types are ball bearings, roller bearings and plain bearings. Common rolling-element designs include deep groove, angular contact, self-aligning and thrust ball bearings, plus cylindrical, tapered, spherical and needle roller bearings. Each design supports a different combination of load, speed and alignment requirements.
Names such as linear bearing, slewing ring, cam follower and mounted bearing describe motion, application or assembly form. These categories overlap: a pillow block can contain a ball bearing, while a slewing ring can use balls or rollers. There is no single fixed number of bearing types unless the classification method is defined.
How Are Bearings Classified?
A bearing supports and guides relative motion between machine parts while transmitting load. Start with how that motion is supported, then narrow the choice by load direction and construction.
Rolling-element bearings use balls or rollers between raceways. Ball bearings are often a starting point for low-friction rotation; roller bearings often provide greater load capacity within a comparable envelope. Actual performance depends on the design.
Plain bearings support sliding motion between surfaces. They include sleeve bushings, thrust washers and spherical plain bearings. Some need an external lubricant supply; others use a self-lubricating material.
Fluid-film bearings support motion on a film of oil or gas. Magnetic bearings use magnetic forces. These are specialist alternatives rather than additional ball or roller bearing designs.
For rotating shafts, radial load acts perpendicular to the shaft axis; axial or thrust load acts along it. An overturning moment tends to tilt the assembly. See the radial vs. axial load guide for load-direction examples.
Bearing Types Comparison: Loads, Uses and Limitations
Use this table to shortlist a design, then check the specific product data. It is not a load-rating or speed-rating table. Axial capacity depends on the exact bearing and its arrangement.
Types of Ball Bearings
Ball bearings use spherical rolling elements. Their small contact regions can provide low friction, but operating speed and load capacity still depend on size, internal geometry, cage, seals and lubrication. The following four designs differ primarily in raceway geometry and load direction.
Deep Groove Ball Bearings
Deep groove ball bearings support radial loads and axial loads in both directions. They are widely used in electric motors, fans, appliances and general machinery where low friction and compact construction matter.
Do not treat their axial capacity as equal to their radial capacity. Check the permitted thrust load, internal clearance and operating speed for the exact bearing. They also require good shaft and housing alignment.
Angular Contact Ball Bearings
Angular contact ball bearings use a contact angle to support combined radial and axial loads. A single-row bearing normally supports axial load in one direction. Opposed pairs or suitable double-row designs can support axial loads in both directions.
A larger contact angle generally favors axial capacity, while smaller angles are often used in high-speed designs. Bearing arrangement and preload affect stiffness, heat generation and life; these settings should come from the application calculation, not a generic rule.
Self-Aligning Ball Bearings
Self-aligning ball bearings have two rows of balls and a common spherical outer-ring raceway. This geometry accommodates a limited angle between the inner and outer rings. They suit primarily radial loading where shaft deflection or mounting alignment is a concern.
Their axial capacity is limited. Check the allowable misalignment for the exact design, including restrictions from seals and surrounding components. Self-alignment does not correct an unsuitable shaft fit or damaged housing.
Thrust Ball Bearings
Conventional thrust ball bearings support axial load and do not carry radial load. Single-direction designs locate a shaft in one axial direction; double-direction designs can locate it in both.
A separate radial bearing is needed when radial forces are present. Verify minimum load and speed limits, because insufficient load or excessive speed can cause poor rolling behavior and heat generation.
Miniature, Thin-Section, Flanged and Ceramic Bearings
These names describe size, proportions, mounting features or materials. They should not be listed as mutually exclusive alternatives to deep groove and angular contact designs.
Miniature bearings suit small mechanisms and instruments. Small size alone does not specify precision, speed or load capacity.
Thin-section bearings reduce the space and mass around a large bore. Thin rings are sensitive to support geometry and fit-induced distortion; a thin section does not automatically mean high speed or high precision.
Flanged ball bearings have an outer-ring flange that helps position the bearing against a housing shoulder. This differs from a bearing supplied in a separate flanged housing.
Ceramic bearings include hybrid bearings with ceramic balls and metal rings, and full-ceramic designs. Metal rings in a hybrid bearing still limit corrosion resistance. Temperature and speed capability also depend on cages, seals, lubrication and fits.
Types of Roller Bearings
Roller bearings use cylindrical, tapered, barrel-shaped or needle-shaped rollers. Their elongated contact regions often provide greater load capacity and stiffness than a comparable ball bearing. This does not mean every roller bearing is slow: some cylindrical roller designs operate at high speeds.
Cylindrical Roller Bearings
Cylindrical roller bearings are primarily radial-load bearings used in gearboxes, motors and machine tools. Their rib arrangement determines whether they permit axial movement or provide axial location.
N and NU designs allow relative axial displacement within the bearing and are commonly used at a non-locating position. NJ designs can support limited axial load in one direction. NUP designs can locate the shaft in both directions, subject to their axial-load limits. Do not read a radial load rating as an axial rating.
Tapered Roller Bearings
Tapered roller bearings support combined radial and axial loads. A single-row bearing supports axial load in one direction and generates an axial force under radial loading. Opposed bearings are commonly used to react these forces and locate a shaft in both directions.
Typical applications include wheel hubs, industrial gearboxes and heavily loaded shafts. Correct endplay or preload is essential; an overly tight setting can increase heat, while excessive clearance can reduce rigidity.
Spherical Roller Bearings
Spherical roller bearings normally use two rows of barrel-shaped rollers and a spherical outer-ring raceway. They support high radial loads, axial loads in both directions and a limited amount of angular misalignment.
They are useful in conveyors, crushers and heavy process equipment where shaft deflection is difficult to eliminate. Permitted misalignment, minimum load, clearance and speed remain specific to the bearing and operating conditions.
Needle Roller Bearings
Radial needle roller bearings use slender rollers to carry radial loads within a small radial cross-section. They suit compact transmissions, pivots and mechanisms with restricted housing space.
A radial needle bearing should not be assumed to carry axial load. Separate needle thrust bearings and combined designs are available for other load requirements. If the shaft runs directly against the rollers, its hardness, surface finish and geometry must meet raceway requirements.
Roller Thrust Bearings
Roller thrust bearings are intended for high axial loads, but their ability to carry radial load varies. Cylindrical and needle roller thrust bearings are generally axial-load designs. Spherical roller thrust bearings can carry axial load together with radial load within the manufacturer’s specified limits and can accommodate limited misalignment.
Crossed Roller Bearings
Crossed roller bearings use alternating roller orientations to support radial, axial and moment loads in a compact arrangement. They are used in rotary tables, robot joints and positioning equipment.
Their rigidity depends on the bearing, preload, mounting seats and clamping structure together. Housing distortion or incorrect bolt tightening can impair running accuracy even when the bearing itself is precise.
Plain Bearings: Sleeve, Thrust and Spherical Designs
Plain bearings support sliding rather than rolling contact. A sleeve bushing supports a shaft radially; a thrust washer supports axial load; a spherical plain bearing allows angular movement between mating spherical surfaces. A spherical plain bearing is different from a spherical roller bearing.
Materials include bronze, engineered polymers and metal-backed composites. Plain bearings are often useful for oscillation, limited installation space or conditions where a simple replaceable sliding surface is preferred. Fluid-film journal bearings are another plain-bearing arrangement and can serve high-speed machinery when the lubrication system is properly designed.
Check bearing pressure, sliding velocity, temperature and the material’s pressure–velocity limits. Do not prescribe grease to every plain bearing: some liners are intended for dry operation, while others require a defined lubricant supply.
For bushing materials and construction, see the sleeve bearing guide.
Linear Bearings, Mounted Units, Slewing Rings and Cam Followers
These useful product categories describe how a bearing is used or installed. They can contain rolling or sliding elements, so they overlap with the classifications above.
Linear Bearings
Linear bearings guide straight-line travel. Options include recirculating ball bushings on round shafts, profiled rail guides using balls or rollers, and sliding bushings. The travel direction is not the load direction: guide assemblies can resist transverse forces and, depending on their geometry, moment loads.
Select for load direction, carriage spacing, rail support, stroke, speed, acceleration and contamination. A housing around a linear bushing is a mounting format, not a separate rolling-element principle.
Mounted Bearings
Mounted bearings combine a bearing with a housing and a shaft-locking arrangement. Pillow blocks mount on a support surface; flanged units bolt against a face; take-up units allow position adjustment, such as for conveyor tensioning.
Check the insert bearing, housing strength, shaft tolerance and locking method as a system. Installation self-alignment in some insert units does not mean the unit can tolerate unlimited shaft deflection during operation.
Slewing Ring Bearings
Slewing ring bearings support large-diameter rotation and often carry axial, radial and overturning loads together. Common designs use four-point-contact balls, crossed rollers or multiple roller rows. They may have internal gearing, external gearing or no gear.
Selection requires the combined load condition, support stiffness, mounting bolts, accuracy and duty cycle. As an illustration, a 1,500 N force acting at a perpendicular offset of 0.20 m creates a 300 N·m moment. That moment must be included in the load assessment; it is not the same as the torque needed to rotate the assembly.
Cam Followers and Track Rollers
Cam followers run directly against a cam or track through a thick outer ring. Stud-type followers include an integral mounting stud. Yoke-type track rollers mount on a separate pin supported by the surrounding structure.
Their main working load is normally radial to the roller axis. Any permissible axial guidance load is design-specific. Check track hardness, contact stress, alignment, outer-ring profile and stud or pin strength, rather than selecting from the internal bearing rating alone.
Specialist Alternatives: Fluid-Film and Magnetic Bearings
Oil-film and air bearings use a fluid layer to separate moving surfaces. Some generate the supporting pressure through motion; others require an external pressure supply. Their suitability depends on start-up behavior, stiffness, load and the fluid supply system.
Magnetic bearings support a rotor with magnetic forces. NASA discusses their potential where long operating life or lubricant contamination is a concern in its overview of magnetically levitated space mechanisms. These systems require a different design assessment from conventional rolling bearings.
How to Choose the Right Bearing Type
Choose a bearing family first, then verify the exact part and its supporting assembly. The following checks keep a general comparison from turning into an unsuitable specification.
Define motion and loads. Record rotation or linear travel, radial and axial forces, overturning moments, shock loads and reversals. Identify whether axial load acts in one direction or both.
Check the whole bearing arrangement. Decide which position locates the shaft and which allows thermal expansion. Review shaft deflection, housing alignment, support stiffness and available space.
Verify speed and duty. Use the actual bearing’s speed limits and operating conditions. Include seals, lubricant, temperature, acceleration, minimum load and intermittent operation.
Calculate load capacity and life. For rolling bearings, check both dynamic and static requirements. A catalogue load rating is not a universal allowable working load. Plain bearings need a different assessment based on their material and sliding conditions.
Specify fits and operating clearance. Mounting interference and temperature differences change internal clearance. Preload is an application decision, not an automatic upgrade.
Plan lubrication, sealing and service. Match the lubricant and protection to contamination, water exposure and temperature. Follow the specified filling quantity and replenishment procedure.
For example, a shaft with 2 kN radial load and 1 kN axial load cannot be selected simply by adding the forces and choosing a bearing rated above 3 kN. The equivalent load depends on bearing geometry and catalogue factors; the shaft arrangement also has to react the axial force. Review the load ratings and bearing life guidance before finalizing a part.
Once the family is selected, use the bearing size chart to check bore, outside diameter and width. Use the bearing number guide to interpret designations and suffixes. Matching dimensions alone does not establish interchangeability.
Maintenance Depends on the Bearing Design
Keep rolling bearings and mounting seats clean, apply installation force through the ring being fitted, and use the specified lubricant. Check changes in temperature, vibration and noise against the machine’s normal condition. A single maintenance interval cannot cover a small sealed motor bearing, an open roller bearing and a slewing ring.
Sliding bearings need maintenance suited to their material and lubrication regime. For all designs, inspect seals, shaft locking and surrounding supports as well as the bearing. Replacing a worn bearing without correcting contamination, poor alignment or an unsuitable fit can repeat the failure.
Frequently Asked Questions
Can I replace a bearing with another type of the same size?
Not on dimensions alone. Different internal designs can change load direction, axial location, stiffness and required clearance. Even bearings with the same bore, outside diameter and width may need different shaft shoulders, mounting procedures or lubrication. Check the complete designation and application requirements before substitution.
Does C3 mean a bearing is more precise?
No. For a bearing to which that clearance classification applies, C3 identifies an internal clearance range greater than Normal. It does not specify running accuracy. Select clearance and precision separately according to fits, temperature and the machine’s accuracy requirements.
Does a higher ABEC rating increase load capacity?
No. ABEC classes describe dimensional and running accuracy for applicable ball bearings; they do not directly specify load rating, seal performance or allowable operating speed. Compare the exact product’s ratings and operating conditions rather than using precision class as a general performance score.
Need Help Selecting a Bearing?
Share the shaft and housing dimensions, radial and axial loads, speed, duty cycle, operating temperature and environmental conditions. Include the existing bearing designation and installation drawing when available. Contact us to discuss suitable bearing options.
About the Author
