Bearing Applications 221

active magnetic bearing

A type of magnetic bearing requiring an external power and monitoring system. Active magnetic bearings can operate at higher temperatures and support a higher load than passive magnetic bearings.

air gap

A small space between the rotor and the stator of a magnetic bearing. An air gap levitates the rotor away from the stator to reduce friction.

alignment

The accurate positioning of parts or components in relation to one another. In a mechanical system, proper alignment is necessary for effective power transmission.

alloy

A metal consisting of a mix of two or more elements, one of which must be a metal. Common alloys include cast iron, bronze, brass, and different types of steels.

angular ball bearing

A type of ball bearing in which the contact angle of the balls to the raceway is angled. Angled ball bearings can accept greater axial load than nonangular ball bearings.

anti-friction bearings

A type of bearing that uses rolling motion to support a load and reduce friction. Anti-friction bearings may also be called rolling-element bearings.

antimony

A blue-white metal used in a wide variety of alloys. Antimony may be found with tin in babbit.

asperity

A microscopic peak on a surface. When objects are in motion, contact between asperities causes friction.

axial load

Force that is applied parallel to a bearing's axis. Axial loads are also called thrust loads or linear loads.

axis

An imaginary straight line that passes through the center of an object. A cylindrical component typically rotates around its axis.

axis of rotation

An imaginary line around which an object spins. The axis of rotation is parallel to and runs through the center of a bearing's shaft.

Babbitt

A metal alloy often used to line plain bearings. Babbitt is commonly made of large amounts of tin with smaller amounts of antimony, copper, and lead.

ball bearings

A type of anti-friction bearing designed with metal balls that provide rolling motion and reduce friction between moving parts. Ball bearings are capable of operating at high speeds but cannot support larger loads.

bearing fatigue

Progressive structural damage to a bearing. Bearing fatigue usually results when a bearing is repeatedly exposed to improper load conditions.

bearing surface

The area of contact between two objects. Bearing surfaces, such as those composing plain bearings, can simply be the surface of a cylindrical hole in which a shaft rotates.

bearings

Friction-reducing devices that allow one moving part to glide past another moving part. Bearings operate using a sliding or rolling mechanism.

bed

The main supporting structure upon which the operating parts of a machine are mounted and guided. Beds provide a foundation for various machine tools.

bore

The distance from one inside edge of an anti-friction bearing's inner race to the opposite edge that passes through the bearing's center. The bore is also called the inner diameter or ID.

boundary lubrication

A type of lubrication in which two surfaces rub together in partial contact. Boundary lubrication, or thin-film lubrication, separates the bearing and shaft with only a thin film of lubricant.

brinelling

Anti-friction bearing damage that appears as indentations in the raceway. Brinelling results from excessive load.

bronze

Any copper-based alloy that does not use zinc or nickel as the primary alloying element. Bronzes commonly contain tin, aluminum, or silicon.

cage

A part found in some anti-friction bearings. The cage separates and prevents the rolling elements, such as balls, from sliding against each other.

carriage

The section of the lathe that supports the cutting tool. The carriage slides back and forth along the ways.

catastrophic failure

The sudden and complete loss of component performance. Catastrophic failure may result from gradual degradation or intermittent failure.

catcher bearing

A secondary, backup bearing. Catcher bearings are used in case magnetic bearings fail or become damaged.

complete lubrication

When a lubricant forms a film that prohibits any contact between two surfaces. Types of complete lubrication include hydrodynamic lubrication and hydrostatic lubrication.

Conrad ball bearing

A type of ball bearing that can accept both radial and axial loads because its cage keeps the bearings from contacting one another. Conrad ball bearings are also called non-fill slot bearings.

contact angle

The angle at which rolling elements of an anti-friction bearing contact the bearing rings. Contact angle size affects the amount of load that bearings can absorb.

contact stress

Force that develops at the points at which two curved surfaces touch one another. Contact stress may cause surface wear or deformation.

contaminants

Damaging foreign material, such as dirt or debris, that causes wear to machine components. Contaminants can cause bearing damage.

copper

A reddish metal that is very ductile, thermally and electrically conductive, and corrosion resistant. Copper may be found with tin in babbit.

crankshaft

A rotating shaft with offset sections that transfer rotational motion into reciprocating linear motion. Crankshafts are used to power the pistons in an engine and to move the ram of a press.

current

The flow of electricity through a circuit. Current is measured in amperes or amps.

cylindrical roller bearing

The most common and basic type of roller bearing designed with cylinders of slightly greater length than diameter. Cylindrical bearings commonly operate in high-speed, high-radial-load environments where axial loads are low.

double-row angular ball bearings

A type of ball bearing consisting of a double row of rolling elements. Double-row angular ball bearings accept a greater amount of load than single-row designs and may be able to carry load in two directions.

double-row spherical roller bearing

A type of spherical roller bearing. Double-row spherical roller bearings can carry 30% more radial load than single-row spherical roller bearings.

double-row tapered roller bearing

A type of tapered roller bearing that consists of a double-row of tapered rolling elements. Double-row tapered roller bearings are able to withstand a significant amount of axial load.

double-row thrust ball bearings

A type of thrust ball bearing consisting of a double row of rolling elements. Double-row thrust ball bearings accept more axial load than single-row thrust ball bearings.

downtime

A period of time when a machine or a facility is neither operating nor producing. Downtime should be avoided whenever possible.

dynamic

The state of an object in motion. Dynamic magnets move against static magnets during magnetic bearing use.

electrical fluting

An extreme form of electrical pitting. Electrical fluting appears as closely spaced lines running parallel to the bearing shaft.

electrical pitting

A sign of damage in improperly lubricated bearings used in electrical equipment. Electrical pitting can appear as either frosted or darkened spots, but it is not always visible to the naked eye.

electromagnetic actuators

A device that produces motion due to an electromagnetic field. Electromagnetic actuators support an active magnetic bearing's rotating component.

electromagnetic forces

Energy from a magnetic field that is produced by the motion of electric charges such as electric current. Electromagnetic forces support the loads placed on magnetic bearings.

energy

The ability to do work. Energy, which is never created or destroyed, may be potential or kinetic and may appear as electrical, mechanical, thermal, or chemical energy.

failure

The complete loss of performance. Failure can be the result of gradual wear, incorrect variables, or insufficient lubrication.

fatigue

Progressive structural damage to a bearing. Fatigue usually results when a bearing is repeatedly exposed to improper load conditions.

fatigue life

The number of times an object can carry a load before it fails. Fatigue life shortens as the stress on the object increases.

fatigue loads

An amount of load that will cause 10% of bearings of a particular type to fail before the end of their expected lifespan. Fatigue loads lead to spalling in anti-friction bearings.

ferromagnetic material

A type of material that is highly attracted to magnets and can become permanently magnetized. Ferromagnetic materials include iron and nickel.

flanged end

A projecting rim or edge. Flanged ends on cylindrical roller bearings are designed to increase stiffness and support greater thrust load.

flat-race thrust ball bearing

A type of thrust ball bearing designed to accept some misalignment. Flat-race thrust ball bearings have a limited ability to accept loads and operate at high speeds.

fluid-film bearing

A plain bearing operating using hydrodynamic lubrication. Fluid-film bearings are also called hydrodynamic bearings.

force

An influence that produces a change in an object's motion or state of rest. Forces have specific directions and magnitudes.

four-row tapered roller bearing

A type of tapered roller bearing that consists of four rows of bearings. Four-row tapered roller bearings are capable of handling a greater amount of radial and axial loads than single-row or double-row tapered roller bearings.

fractures

Cracks or chips in the surface of an object. Fractures in a bearing's raceway are usually a result of stress and excessive loads.

friction

The resistance between the contact surfaces of two objects. Friction generates heat and increases the wear between components.

full-fluid lubrication

A type of lubrication in which a lubricant film will completely separate two surfaces in contact once a bearing rotates quickly enough for the lubricant to flow around the bearing and cover its entire surface. Full-fluid lubrication is also called hydrodynamic lubrication.

gearboxes

An enclosed system of assembled gears that transmits mechanical energy from a prime mover to an output device. Gearboxes can also change the speed, direction, or torque of mechanical energy.

grades

A category, rank, or level of quality. Grades of industrial lubricants are based on their thickness or viscosity.

grease

A semisolid substance composed of oil and a chemical soap or other additive. Grease is commonly used as an industrial lubricant.

grooved-race thrust ball bearing

A type of thrust ball bearing designed with a grooved raceway. The grooved-race thrust bearing can operate at higher speeds and carry a higher load than flat-race thrust bearings.

hub

The central part of a wheel. The hub connects an axle to a wheel.

hydrodynamic bearing

A plain bearing operating using hydrodynamic lubrication. Hydrodynamic bearings are also called fluid-film bearings.

hydrodynamic lubrication

A type of lubrication in which a lubricant film will completely separate two surfaces in contact once a bearing rotates quickly enough for the lubricant to flow around the bearing and cover its entire surface. Hydrodynamic lubrication is also called full-fluid lubrication.

hydrostatic lubrication

A type of lubrication in which moving surfaces are separated externally by a highly pressurized fluid such as air, oil, or water. Hydrostatic lubrication is expensive, and its use is limited.

inner diameter

ID. The distance from one inside edge of an anti-friction bearing's inner race to the opposite edge that passes through the bearing's center. The inner diameter is also called the bore.

journal

A shaft of a journal bearing. The journal is softer than the outer casing of the bearing.

journal bearing

A type of plain bearing designed to provide sliding, rotary motion. Journal bearings, or sleeve bearings, reduce friction by supporting radial loads.

lathe

A machine tool that holds and supports a cylindrical workpiece at one or both ends and rotates it while a single-point cutting tool removes material. Lathes are commonly used to perform turning operations.

lead

A bluish-white metal that is very soft and ductile. Lead may be found with tin in babbit.

length-to-diameter ratio

L/D ratio. A numerical expression of the relationship between the length and diameter of an object. Greater length-to-diameter ratio of the rolling elements in roller bearings increases radial load capacity.

levitation

To float or hover in the air. Levitation of a magnetic bearing's rotor is achieved by magnetic forces.

linear bearing

A type of plain bearing designed to provide sliding, linear motion. Linear bearings, or linear-motion bearings, reduce friction by supporting linear loads.

linear load

Force that is applied parallel to a bearing's axis. Linear loads are also called axial loads or thrust loads.

linear motion

Movement along a straight line. Linear motion is one of two basic forms of motion that mechanical energy can take.

linear-motion bearing

A type of plain bearing designed to provide sliding, linear motion. Linear-motion bearings, or linear bearings, reduce friction by supporting linear loads.

load

The overall force applied to a material or structure. Loads may be either radial or axial.

lubricant

A substance used to reduce friction between two surfaces in relative motion. Common industrial lubricants include oil and grease.

lubrication

The use of a slippery substance, such as oil or graphite, between two moving surfaces that are in contact with each other. Lubrication minimizes friction, which aids movement and reduces heat.

machine tools

A very general term for any powered machine that is used to manufacture parts by guiding a tool. Common examples of machine tools include the saw, the drill press, the lathe, and the mill.

machines

A device consisting of two or more parts that transforms energy into motion. Machines are used to transmit or modify force and motion so as to accomplish some form of useful work.

magnetic bearing

A bearing that uses magnetic forces to support a rotating shaft and carry a load. Magnetic bearings are an alternative to more common bearings in operations that require very low friction, high precision, and extremely high speeds and operating temperatures.

magnetic field

The area in and around a magnet in which a magnetic force exists. Magnetic fields exhibit the powers of attraction and repulsion.

magnetic levitation

The process of lifting an object in the air using magnetic fields. Magnetic levitation allows magnetic bearings to support loads with low-friction, non-contact motion.

magnetizes

To make a material magnetic or attractive to other metals. Applying electrical current to ferromagnetic material will magnetize it.

mechanical force

Force created by the movement of an object over a distance. Mechanical forces are created when one moving object comes into contact with another object.

mechanical system

A collection of machines functioning together to perform useful work. All modern mechanical systems are based on simple machines.

misalignment

The inaccurate positioning of parts in a mechanical system in relation to one another. Misalignment can sometimes cause damage to system components.

mixed-film lubrication

A transitional stage of lubrication that occurs after boundary and before hydrodynamic lubrication. Mixed-film lubrication allows for contact between two moving surfaces and increases friction.

monitoring system

A group of devices that collect and report performance data regarding a machine or a machine component. Monitoring systems are used in conjunction with active magnetic bearings.

motion

A change in an object's original position as a result of a force applied to the object. Motion is typically described in terms of displacement, direction, velocity, acceleration, and time.

needle roller bearing

A type of cylindrical bearing with long, thin rollers at least four times greater in length than their diameter. Needle roller bearings have the highest radial load capacity in relation to their length of all roller bearings.

non-fill slot ball bearing

A type of ball bearing that can accept both radial and axial loads because its cage keeps the bearings from contacting one another. Non-fill slot bearings are also called Conrad ball bearings.

notches

An angular or V-shaped cut or indentation in the races of some ball bearings. Notches in the race of a slot-fill bearing allow for the addition of extra balls.

oil

A slippery fluid commonly used as a lubricant. Both natural and synthetic oils are used in industrial applications.

oil inlet

An opening on a bearing. Oil inlets allow lubricant to be applied to a bearing.

outer diameter

OD. The distance from one outside edge of an anti-friction bearing to the opposite edge that passes through the bearing's center. The outer diameter indicates an anti-friction bearing's overall size.

parallel

Two lines that are equidistant from one another. Parallel forces that are applied to a bearing's axis move in the same direction as the axis rather than approaching the axis directly.

passive magnetic bearing

A type of magnetic bearing that does not require an external power or monitoring system. Passive magnetic bearings are not capable of operating under temperatures or loads as high as active magnetic bearings.

permanent magnets

A magnet that has a constant attractive force and is always "on." Permanent magnets are used in passive magnetic bearings.

perpendicular

An angle formed by two lines at a 90° right angle. Perpendicular forces that are applied to a bearing's axis approach the axis directly rather than moving in the same direction as the axis.

plain bearing

A type of bearing that uses a sliding motion to reduce friction. Plain bearings are also called solid bearings.

plastic

A material characterized by its light weight, high corrosion resistance, high strength-to-weight ratios, and low melting points. Plastics are often easily shaped or formed.

power source

A device that generates electricity. Power sources include generators, motors, and batteries.

powertrain

A series of automotive components that generate and deliver power. Powertrains include an engine, transmission, and other components.

pressure

The exertion of force upon a fluid. Pressure can cause changes to the properties of a fluid.

race

The outer and inner ring of an anti-friction bearing that encase the rolling mechanisms. Races are notched, grooved, or flat.

raceway

The groove within an anti-friction bearing that runs along the middle of the inside and outside bearing rings. The raceway provides a path for the bearing's rolling mechanisms.

radial clearance

The useful space that is intentionally maintained between a bearing's balls and its raceway perpendicular to its axis. Radial clearance can be adjusted during bearing assembly or installation.

radial load

Force that is applied perpendicular to the axis of a bearing's shaft. Radial loads are also called rotary loads.

roller bearings

A type of anti-friction bearing designed with rollers that provide rolling motion and reduce friction between moving parts. Roller bearings demand slower speeds than ball bearings, but they can support greater loads.

rolling-element bearings

A type of bearing that uses rolling motion to support a load and reduce friction. Rolling-element bearings are also called anti-friction bearings.

rotary load

Force that is applied perpendicular to the axis of a bearing's shaft. Rotary loads are also called radial loads.

rotary motion

Movement in a circular direction. Rotary motion is one of two basic forms of motion that mechanical energy can take.

rotor

The rotating component of a magnetic bearing. The rotor is used together with a stationary part, the stator.

scoring

Damage done to plain bearings due to direct contact between moving parts. Scoring appears as long scratches in the direction of motion.

service life

The length of time a bearing is expected to be in operation before being replaced. Service life can be shortened by improper operating conditions and lack of preventive maintenance.

shaft

In a mechanical system, a cylindrical bar used to support rotating components or to transmit power or motion by rotation. Bearings operate by limiting the friction applied to shafts.

single-row angular ball bearings

A type of ball bearing consisting of a single row of rolling elements. Single-row angular ball bearings accept less load than double- and multi-row designs and may support load in one direction only.

single-row tapered roller bearing

The most common type of tapered roller bearing consisting of a single row of tapered rolling elements. Single-row tapered roller bearings can take both high radial and high axial loads in only one direction.

single-row thrust ball bearings

A type of thrust ball bearing consisting of a single row of rolling elements. Single-row thrust ball bearings accept less axial load than double-row thrust ball bearings.

sleeve

A tubular part designed to fit over another part. Sleeves of plain bearings are usually made of a hard metal and lined with a softer metal.

sleeve bearing

A type of plain bearing designed to provide sliding, rotary motion. Sleeve bearings, or journal bearings, reduce friction by supporting radial loads.

slot-fill bearing

A type of ball bearing that can accept relatively high radial loads, but very little thrust. Slot-fill bearings contain notches in the inner and outer rings that permit filling the bearing to capacity with balls once it has been installed and aligned.

solid bearing

A type of bearing that uses a sliding motion to reduce friction. Solid bearings are also called plain bearings.

solid lubricants

A nonflowing substance used to reduce friction between two surfaces in relative motion. Solid lubricants include graphite.

spalling

Anti-friction bearing damage that appears as fractures in the raceway. Spalling results from normal use or excessive load.

speed

The rate at which an object travels in a given period of time. Speed is used to measure both linear and rotational movement.

spherical roller bearing

A type of roller bearing featuring a barrel shape. Spherical roller bearings are able to carry some axial load in addition to high radial load.

startup friction

The initial friction caused when a machine begins operation. Startup friction is greater than the friction that takes place once components are in motion.

static

The state of an object at rest. Static permanent magnets remain fixed in one place during magnetic bearing use.

stator

The stationary component of a magnetic bearing. The stator is used together with a rotating part, the rotor.

steel

A metal consisting of iron and carbon, usually with small amounts of other elements. Steel is the most common manufacturing metal.

tapered roller bearing

A type of roller bearing featuring tapered inner and outer ring raceways and rollers. Tapered roller bearings can withstand high radial and axial loads.

Teflon

A fluorocarbon solid that may be used to coat surfaces. Teflon is commonly used to reduce friction between two moving components.

thin-film lubrication

A type of lubrication in which two surfaces rub together in partial contact. Thin-film lubrication, or boundary lubrication, separates the bearing and shaft with only a thin film of lubricant.

thrust ball bearing

A type of ball bearing designed with its balls oriented perpendicular to the axis of rotation. Thrust ball bearings are able to handle a great deal of axial load.

thrust clearance

The useful space that is intentionally maintained between a bearing's balls and its raceway parallel to its axis. Thrust clearance can be adjusted during bearing assembly or installation.

thrust load

Force that is applied parallel to a bearing's axis. Thrust loads are also called axial loads or linear loads.

tin

A silver-white, soft metal used in many alloys. Tin is often used to coat other metals to prevent corrosion.

viscosity

The resistance to flow of a fluid or semifluid substance. Viscosity describes how easily a substance flows.

washers

A thin disc with a hole in the middle used to support load. Washers are used to support thrust ball bearings.

ways

Two precisely measured, parallel tracks that support and guide the movement of machine components. On a lathe, ways support and guide carriage movement.

wear

The erosion of material as a result of friction. Wear typically is caused by two or more objects rubbing or sliding against each other.

work

The result of a force applied to an object and the distance through which the force is applied. In an equation, work is force multiplied by distance.