Abbreviated designation
See Designation

Abott curve
A visual representation of surface of material components (load supporting components) showing core, peak and trough areas.

Material worn away from the functional surface by tribological loading.

Abrasive wear
Wear due to abrasion

Inclusion of gases or vapours by fluids or solid bodies, for example lubricants or bearing materials.

Abutment shoulder
Shoulder in the surrounding structure for transfer of forces and location of components.

Deviation of the actual dimension from the nominal dimension as described by tolerances. For monorail systems, the parallel deviation of the reference surfaces within given tolerances.

Running accuracy
Dimensional Accuracy

Accuracy classes
Division of the tolerances into classes;
for example, rotary bearings into PN, P6, P5 to DIN 620 and linear bearings into G0 to G4.

Active ingredients
Lubricant additives. Improves pour point, viscosity/temperature ratio and corrosion protection; prevents oxidation and ageing; reduces wear and foaming.

See Additives

An accessory mounted on another element, for example a lubrication adapter

Lubricant additive to improve viscosity-temperature behaviour or pour point, prevent corrosion, oxidation or ageing or reduce wear or foaming

Binding force of a body to another body, e.g. a lubricant to a surface

Adhesion friction
See Lubricant
Adhesion properties
Characteristics of a lubricant in adhering to frictional elements.

Adhesion wear
Caused by the mechanism of the formation of a local adhesion connection and subsequent tearing off of solid bonds connected with material break-up and transfer (DIN 50323-2).

Adjacent construction
The immediate environment of the bearing; the bearing and adjacent construction have a reciprocal influence on each other
Adjusted bearing arrangement

Semi-locating bearing arrangement in X or O arrangement with adjusted clearance or preload.
Adjustment side

The side parallel to the datum side in a linear guidance system.

Holding of gases, vapours or fluids on the surface of solid bodies e.g. lubricants on the surface of friction elements.
Aerodynamic lubrication
Lubrication at friction points by gas which completely separates friction elements.

Aerostatic guidance
"Air bearing" in which the friction partners are separated by gas

Chemical changes in material due to heat, pressure, foreign materials and other influences
Aluminium complex base grease
Grease based on an aliminium complex soap with mineral and/or synthetic oil. Preferred applications:
- bearing lubrication at high temperatures,
- sprayable adhesion lubricants for large open gearboxes.

Aluminium soap base grease
Grease based on aluminium soap and mineral oil.
Ambient temperature

Temperature at the friction point without relative movement between friction elements.

Angular misalignment
See Misalignment error

Heat treatment intended to give a hardened and relatively brittle material a higher strength.

Annealing temperature
Temperature in the range of 160° to 650° which causes annealing.

Apparent dynamic viscosity
Internal friction (lubricant friction) of a lubricant. Dependent on the composition of the lubricant, the temperature and the speed.
Armature grease
Special grease with particular characteristics with respect to gases, vapours, fluids, rubber seals and/or characteristics matched to drinking water, food etc.
Applications: valves, ball and tap cocks, sliders.

Aromatic coumpounds
Ring-shaped, unsaturated carbon compounds. As a base oil these are not resistant to ageing and have an unfavourable viscosity/temperature ratio and a low pour point.

Arrangement of bearings
Installation in accordance with the operating conditions and selection of bearing type, for example as locating bearing/non-locating bearing arrangement, adjusted bearing arrangement, semi-locating bearing arrangement
Arrangement of raceways
The relative position of the raceways of rotary or linear bearings, for example tandem, X or O arrangement
Axial bearing clearance
The amount by which the bearing rings in a bearing before fitting can be moved in an axial direction from one extreme position to the other without axial loading.

Axial clearance
The amount by which the bearing rings in a fitted bearing can be moved in an axial direction from one end position to the other without axial loading.

Axial deflection
The force/distance ratio in bearings loaded in the axial direction clearance-free.

Axial displacement
Travel in an axial direction due to axial clearance and deflection

Axial factor
The multiplier "Y" for axial loads in combined loading in order to calculate the equivalent load.
Axial load
Force acting in the direction of the shaft.

Axial location of bearing rings
Form or friction locking of rolling bearing rings in order to prevent axial movement.
Axial rigidity
Resistance of a bearing to an axial load

Axle bearing
On rail vehicles, the wheelset roller bearing.

Also known as UIC bearings as the housing mounting dimensions and the dimensions of the axle stub are standardized by the international railway union (UIC)


Material structure. Characteristics:
- hardness, covering and dimensional stability lower
- strength higher than martensite

Base oils
Main component of oils and greases for lubrication.

The oil used in the soap component of a grease. The base oil forms approximately 70% to 95% of the grease.

Bearing adjacent components
The machine components adjacent to the bearing

Bearing arrangement
Arrangement of bearings, for example locating/locating, semi-locating/semi-locating, non-locating/non-locating, or semi-locating bearings in tandem, O or X arrangement
Bearing clearance

See Bearing internal clearance

Bearing deflection
Reciprocal displacement of bearing parts under the influence of an external load

Bearing internal clearance
In rotary bearings without load, the reciprocal, stress-free displacement of the bearing rings in the bearing plane (radial internal clearance) or the bearing axis (axial internal clearance); in linear bearings, the displacement of the bearing transverse to the direction of motion

Bearing rigidity
See Rigidity
Bearings with increased capacity
have the suffix R.

Behaviour with respect to water
Parameter for greases in accordance with DIN 51 807 part 1. The test result is a characteristic factor. The change in the grease is assessed after a static period of 3 hours.
0 = no change
1 = minor change
2 = medium change
3 = major change

Concertina type, extendable cover for protecting linear guidance systems

Separated base oil in bearing arrangements or with mechanical thermal loading.

Bore parameter
Designation for the bearing bore diameter d, in accordance with DIN 623.

Boundary friction
Friction condition with intensive contact of surface roughnesses; friction bodies coated with thin lubricant film; unacceptably high wear

Boundary lubrication
Lubrication condition in friction sites under boundary friction; friction bodies coated with thin lubricant film; intensive contact of surface roughness; unacceptably high wear




The part of a rolling bearing which separates, retains and, where necessary, guides the rolling elements

Calcium soap base grease
Grease based on calcium soap and mineral oil. Bery good resistance to water. Suitable for use as sealing grease for labyrinth seals. Previously used as automotive grease.
Calculation of running time
See Operating life
Calculation program
See INA EDP program

Thermo-chemical case hardening. Steels with carbon content of approximately 0,1 to 0,25% are carburized up to approximately 0,8 to 0,9%, case hardened and surface layer more resistant to wear.

See Maintenance
Central lubrication
Automatic supply of lubricant from a central location to lubrication points
Chemical reaction
Conversion of bodies into others.

See Chromium plating
Chromate passivation
Non-metallic coating, protective layer with a thickness up to 15 µm. Caused by immersing steel or aluminium components in hot phosphoric acid and heavy metal phosphate solutions.
Chromium layer
Chromium layer. Galvanic coating by electrolysis.

Chromium plating
Thermo-chemical corrosion protection in which the surface layer of a material is enriched with chromium by up to 35%. Used instead of corrosion resistant materials.

Chromium steel
Rolling bearing steel, e.g. 100 Cr 6 with chromium a main alloy component. Through or case hardening surface layer.

Friction locking of two components.

Surface technology to improve tribological behaviour, corrosion resistance, e.g. by INA Corrotect and for electrical insulation.

Coefficient of friction
Dimensionless value for friction from the ratio of the frictional force to the normal force.
Cold welding
Welding of solid elements at ambient temperature. The roughness peaks have immediate contact. The harder roughness peaks press into the soft surface. A metal bridge forms between the friction elements which prevents the relative movement of these elements with respect to each other. The metal bridge is stronger than the frictional force.

Combined load
Indication of a force acting in a non-perpendicular direction on the bearing.
Load angle b not equal to 0° or 90°.
Complex grease
Lubricating grease based on metal soaps, made from fatty acids with a high molecular weight.

Compounded lubricant
Grease lubricant with mineral oil base with grease oil as active ingredient.

An indication of the deformability of a lubricating grease

Consistency enhancer
See Thickener
Contact angle
Operating contact angle
Nominal contact angle

Contact corrosion
Corrosion of an area of metal in a metal/metal contact. The cause of corrosion is a local element. The corroded metal is the anode of the local element.
Contact direction
Operating contact angle
Nominal contact angle

Contact seal
See Seal

Contact surface
The contact surface between two bodies under load, calculated according to Hertz

Continuous feed lubrication
Lubrication method in which the friction points are repeatedly supplied with lubricant throughout their life.

Continuous operation
Guide line for operating time for selection of rolling bearings with dynamic loading.

Reaction of a metallic material with its environment.

Corrosion protection
Platings and coatings applied to metallic materials to protect against corrosion

Thin, galvanic plating containing zinc alloys (binary, ternary) applied to hardened rolling bearing raceways for corrosion protection

Device for protecting guidance elements against contaminants, swarf, coolant lubricants and mechanical damage.

Covering strip
Strip for covering drilled holes to give a smooth surface

Crash safety
Security of a component against failure under extreme load

Crevice corrosion
See Fretting corrosion

Crowning - rolling element
See End profiling

Cylindrical rollers
Cylindrical rolling elements sorted to diameter and length, suitable for transmitting normal loads via their cylindrical and end faces (DIN 5402, Part 1)

See Rolling element


Loss of essential or required characteristics in equipment, machinery or plant or their component parts.

A reduction in the amplitude of an oscillation (DIN 53 513)

Datum side, datum rail
The side of a guidance system from which dimensional and geometrical tolerances are measured

The ability to absorb energy over a certain distance, to store this completely or partially as deformation energy and to release the energy when the load is removed (hysteresis)

Deflection coefficient
Non-dimensional value calculated from the deflection of the bearing in the clearance-free condition and with clearance

Deflection constant
See Deflection coefficient

Deflection curve
Indicates the deflection force or moment as a function of deflection distance or torsion angle.

Undesired modification of the form of a solid body due to force.

Mass ratio of a lubricant with respect to its volume to DIN 51 757.

Usual units for solid materials (apparent density):

  • gramms per cubic centimeter g/cm3


  • gramms per millilitre g/ml


  • kilogrammes per cubic meter kg/cm3

Other permissible units are kg/dm3, kg/cm3, kg/l

Identification of a bearing by letters and numbers, indicating, for example, the series, dimensional series or size code, bore diameter, bearing design and information such as Corrotect plating or length of guideways

Detergents are defined as metallo-organic compounds (e.g. alkyl salicylate, phenolates and sulphonates) which prevent the formation of combustion residues, corrosive wear and corrosion.

Diester oil
Synthetic oil from the reaction of an alcohol with an organic acid.
Differential slippage
Also known as microslippage, the deviation of the circumferential speed from the calculated (theoretical) circumferential speed due to flattening and raceway curvature-
Dimensional accuracy
Defined tolerances which allow allocation of a rolling bearing to a particular accuracy class to DIN 620.

"Dispersant" additives are generally defined as ash-free compounds (e.g. succinimide) which cause fine dispersion and suspension of combustion residues in the engine oil.

Volatile solvent which disperses or dissolves lubricants but which does not chemically modify them.

Insoluble materials in a fluid or gas which are distributed throughout a system.

Distance ring
Ring which keeps components at a specific distance from each other.
Drilling friction
Relative rotation of two bodies in contact but rotating about non-parallel axes; leads to severe tribological stress.

Drive drum
The driven drum in a belt conveyor system for other bulk transportation of materials.

Drop point
Temperature at which the lubricant forms a elongated drop under standard test conditions. This parameter is not a guide value for the upper operating temperature.
ISO 2176.

Dynamic friction
Friction between two friction elements moving with respect to each other.

Dynamic load
The term dynamic indicates that the operating condition is with the bearing rotating. This is not a variable load.


Effective power
To DIN 1940, the power available for the connection of drive elements (e.g. internal combustion engine) after taking all the power used to drive ancillary equipment. The SAE standard does not take into consideration these losses in power and the engine power given there is therefore higher.

Elastic deformation
Occurs between the rolling elements and the raceways in loaded rolling bearings providing the lubricant satisfies Hooke_s law.

See Cold welding

Elastic expansion
Expansion of the inner ring in bearings due to tight fits or centrigufal forces at very high speeds.

Reciprocal of Rigidity
Emergency running characteristics
Ability of a lubricant to reduce wear in boundary, partial or defective lubrication. Oils or greases contain active ingredients which form a reaction layer on the surface or solid luricants such as molybdenum disulphide which improve the quality of the surface.

End profiling
In rollers, a curved taper of the diameter towards the end faces in order to reduce or eliminate edge stresses
Engine oil
Oil for petrol and diesal engines. The engine oils are subdivided into viscosity classes to DIN 51 511.

EP additive
Additive to prevent the adhesion of lubrication points under high mechanical stress and reduce wear
Equivalent dynamic bearing load
See Equivalent dynamic load

Equivalent dynamic load
Summary of time and load components for calculation of the bearing operating life where load and speed are not constant.

The equivalent dynamic load is to be used if:

  • load is not constant,

  • forces do not act perpendicularly,

  • the bearing performs oscillating movement,

  • a force with a constant magnitude and direction is

  • replaced by a circumferential force

Equivalent static bearing load
See Equivalent static load

Equivalent static load
Formed by the radial and axial components of combeined loads. Results in the same surface pressure between rolling elements and raceways as the actual, effective combined load.

Unwanted reduction in operating value of components due to the effect of mechanical, chemical, thermal and/or electrical energies.

Etching marks
Appearance of corrosion on rolling bearing raceways cased by, fro example, unsuitable grease.
External bearing arrangement
For example, if take-up units are arranged outside the drum.

Extraction thread
Thread for screws or nuts with which the bearing is pushed out of its seating.


Failure distribution
The spread of fatigue times for similar bearings with similar loading for a large number of rolling bearings.

Failure probability
In arranging bearings by their running time, the number of these which have failed by a certain time can be ascertained and the failure probability given in a Weibull diagram.

False brinelling effect
Indentations (troughs, furrows) on the raceway caused by shaking during stationary periods due to vibratory frictional wear.

Structural changes, apparent as surface delamination, caused by a large number of overrolling movements under load

Fatigue strength
The condition for rolling bearings where the life curve determined in tests tends to the horizontal. Assumes relevant Hertzian pressure, extremely high cleanliness and good lubricant distribution in the rolling contact.

See Operating life
Fatty acids
Organic acids, insoluble in water, which can form metal salts (metal soaps) with base elements. Metal soaps such as aluminium, calcium, lithium or sodium soap swell in oils and thicken them.
Fatty oils
Animal and plant oils and greases such as cattle foot oil, bone oil, ewe or beef tallow, wool fat. Fatty oils are not resistant to ageing. They tend to harden and precipitate aggressive fatty acids. The active ingedient is the mineral oil polarity.

Felt lubrication
Lubrication method in which the lubricant is guided to the friction point by felt.

Fire cracks
Fine cracks on rolling bearing rings caused by overheating due to friction.
Fire point
Lowest temperature at which an oil vapour can be ignited by external ignition to DIN ISO 2892.

Flaking, peeling
Loosening of the surface in a rolling bearing caused by Hertzian pressure. Based on normal fatigue or irregularities.

Flash temperature
Localized temperature up to 1000°C occurring in a friction point with relative movement. The surface roughnesses are either sheared and/or plastically spread.

Flowable grease
Soft grease with more or less flowable structure, conforming to NLGI classes 0 to 000 according to DIN 51818; areas of application include central lubrication systems, closed gearboxes
Fluid friction
Friction condition in which the friction partners are completely separated by a complete fluid film.

Reciprocal of viscosity

Foreign particles
Foreign materials occurring in lubrication positions or friction points due to environmental influences.

Four point contact
Description of the contact relationship in a ball bearing in which the balls have four points of contact with the raceways

Surface damage in which the separated surface of the damaged area displays predominatly break characteristics (DIN 50323-2).

Fretting corrosion
Local corrosion on metallic surface caused by friction or effects of external heat.

The resistance to relative movement of two bodies in contact with each other; subdivided into friction terms, friction types and friction conditions
Friction from movement
Term for friction caused by two bodies moving relative to each other.
Friction types
Classification of movement friction according to type of movement and type of friction body (DIN 50281)
Frictional corrosion
See Fretting corrosion

Frictional force
Mechanical resistance in the contact area of contacting, solid elements. The frictional force restricts the relative movement due to dynamic friction or prevents it due to static friction.
Frictional oxidation
See Fretting corrosion

Frictional value
See Coefficient of friction
Frictional value µ
See Coefficient of friction
Full complement
Design of rolling bearing with the largest possible number of rolling elements (balls or rollers) by the omission of cages or cage elements

Full lubrication
Lubrication condition in the friction points for fluid friction. The friction elements are completely separated by the fluid lubrication film. There is no wear.


Gap seal
A contact-free and friction-free seal, for example a sealing shield or end seal of a monorail guidance system
Gearbox oil
Oil with a mineral oil basis for spur gear units and worm gear units to DIN 51 509.

Gel grease
Grease based on an inorganic thickener (bentonite or micro-dispersed silicic acids) with a mineral oil and/or synthetic oil. Grease without dropping or melting point. Preferred applications: bearing lubrication at high temperatures.

Geometrical defect
Deviation from the ideal geometry
Geometrical deviation
See Deformation

Solid lubricant with layered grid structure. Suitable for dry running or as active ingredient in oils or greases. Graphite absorbs moisture. Graphite displays its best lubrication characteristics in damp environments.

Grease cartridge
Fatty acids

Grease cartridge
Special grease packaging. Grease does not need to be transferred from a container into the grease gun. The opened grease cartridge is simply pushed into the grease gun.

Grease change interval
See Lubricant change interval

Grease lubricants
Lubricants with a mineral oil base with fatty oil as the active ingredient.
Consistent grease with a mineral oil and/or synthetic oil base with thickener as well as active ingredients or additives. See DIN 51 825 part 1 for demands on greases, grease type K, operating temperature range -20 to 140°C or DIN 51 825 part 2, for grease type KT.
Groove seals
See Gap seal

Guidance accuracy
Accuracy of the whole guidance system, dependent on the accuracy of the linear rolling element guidance system, design of the guidance system and accuracy of the adjacent construction


Resistance of a body to indentation by another body; hardness is either intrinsic or is achieved by heat treatment processes (steel) and/or thermochemical diffusion; for rolling bearings, hardness is measured in Rockwell (HRC) or Vickers (HV)

Hardness depth
Depth of a hardened surface zone at which a hardness of 550 HV is still present (DIN 50190)#
Hardness depth, minimum
This depends essentially on the rolling element diameter, the material stress, the core strength and the hardening process
HD additive

Heat build-up
See Operating temperature

Controlled heating to approximately 80°C above room temperature by, for example, induction heating equipment electric ovens, heating plates or clean oil baths for easier assembly.

Heating equipment
Equipment for induction heating of bearings.
Hertzian pressure
Pressure between two bodies in point or line contact with curved surfaces; can be calculated according to Hertzian theory

High pressure lubricants
Lubricants which contain EP (extreme pressure) additives to prevent adhesion and severe wear in the mixed friction area

High speed grease
Grease for very high speeds. it is usually possible to use these greases over the permissible speed range for grease lubrication for rolling bearings.

High temperature grease
Grease for high operating temperatures > 140°C.

High viscosity lubricant
Lubricating fluid with high internal friction or grease with viscous (thick) base oil.
Hollow roller cage
Machined cage in which hollow cylindrical rollers are held by a pin through the bore.
See Mounting dimensions

Hydraulic oils
Pressure fluids (HLB to DIN 51524 Part 2) comprising mineral oils with active agents for increased corrosion protection, ageing resistance and reduced fretting wear in the mixed friction area
Hydrodynamic lubrication
The relative motion between the friction partners forms the lubricant film (contact whilst stationary and mixed friction during starting)
Characteristic of a grease - ability to absorb moisture.

Characteristic of a grease - ability to repel moisture.

Hydrostatic guidance
Plain bearing guidance in which the pressure for the lubricant film is generated outside the bearing

Hydrostatic lubrication
Pressure in the lubricant generated outside the bearing, forms the lubricant film between the friction partners (the friction partners are separated even when stationary)

See Rigidity


Idler pulley unit
Pulley usually set on a loose drum to tension belts and chains
INA data sheet
Form for recording all characteristics required for processing, for example for calculation

INA EDP program
Calculation programs for determining

  • basic and adjusted rating life

  • static load safety factor

  • displacement due to the elasticity of the bearing arrangement

  • lubrication, etc.

INA software
See INA EDP program

See Angular misalignment

Injection lubrication
Recirculating lubrication in which the lubricant is sprayed into the friction point.

Control and assessment of lubrication and friction points on equipment and machines.

Abbreviation for International Organisation for Standardization.

Abbreviation for ISO viscosity grade.




Layered grid
See Solid lubricant

Life, rating
The basic rating life is the life reached or exceeded by 90% of a sufficiently large group of apparently identical bearings before the first evidence of material fatigue develops

Limiting temperature values
See Operating temperature

Linear guidance system
Bearing which supports motion on straight raceways, for example: linear rolling element and plain bearings, yoke and stud type track rollers on shafts, guideways or other straight raceways with limited or unlimited stroke

Linear rolling bearing
See Rolling bearing

Lithium complex grease
Lubricating grease based on lithium complex soap, mineral oil and/or synthetic oil

Lithium complex soap base grease
Grease with a lithium complex soap with mineral oil and/or synthetic oil. Preferred applications: bearing lubrication with high temperature, long-term and continuous operation for rolling bearings.

Lithium soap grease
Lubricating grease based on lithium soap, mineral oil and/or synthetic oil

Load which, for example, is to be supported at a friction point. Also strain from pressure and/or heat.

See Contact surface

Load direction
Effective direction of a load

Load factor
Factor taking into consideration the axial and moment loading in the calculation of the load safety and rating life.

Load flow
Path of a load, for example through a bearing and adjacent parts.

Load supporting component
Relationship between theoretical and actual contact surface in a friction point.

Load supporting area
Surface condition of the load supporting element in a friction point.

Load type
Normal loads, transverse loads and moments occurring individually or jointly, either constant or varying in time, direction and magnitude

Loading, loading point
Point at which a load acts within the co-ordinate system

Locating bearing
Bearing capable of transmitting axial loads from both directions and radial loads

Locating face
The machined surface of a machine part used for alignment, for example, of a guideway or carriage

Logarithmic profile
End profiling of a roller corresponding to a section of a logarithmic spiral

Long-term lubrication
Lubrication method in which the lubricant is effective in the friction point for longer periods of time.

Low temperature grease
Grease for low operating temperatures < -20°C. Requirements to DIN 51 825 part 2, grease type KT.

Low viscosity lubricant
Lubricant fluid with low internal friction or grease with light fluid (thin) base oil.

Gaseous, fluid, consistent, plastic or solid material for reduction of friction and wear between two friction elements.

Lubricant change
Change of lubricant e.g. replacement of used lubricant by fresh lubricant or change from normal lubricant to special lubricant.

Lubricant change interval
Time period up to the lubricant change. The lubricant has reached its operating life.

Lubricant film
Layer separating the sliding or rolling partners

Lubricant paste
Consistent lubricant with a mineral oil and/or synthetic oil base with or without thickener, active ingredients or additives as well as high solid lubricant content.

Lubricating oil
Oil without specific active ingredients. Available as a distillate or raffinate. Usual grouping
- light machine oil ISO VG 32
- medium weight machine oil ISO VG 68
- heavy weight machine oil ISO VG 100, 150 and 220.

Lubricating oil CGLP
Slideway oil with synergetic combination of agents to prevent stick-slip

Lubricating oil CLP to DIN 51 517, part 3
Mineral oil with active ingredients to increase the corrosion protection and resistance to ageing (L) as well as to reduce wear in mixed friction applications (P).

Feed of fresh lubricant to friction points. Fresh lubricant mixes with used lubricant at the friction point. Lubricant feed is by means of lubrication equipment. The time period for relubrication is shorter than that for the lubricant change interval.

Lubrication method
Lubrication condition
Recirculating lubrication
Lubrication technology
One-off lubrication
Hydrodynamic lubrication
Lubricant change intervall
Lubricant change
Lubricant paste
Lubricant film
Lubrication system

Lubrication condition
Classification of the separation and/or contact of lubricated friction elements.

Lubrication method
Feed of lubricant to the friction points.

See Lubricant

Lubrication system
Fixed system for feeding lubricant to friction points. The feed and metering of lubricant is either partially or fully automatic.

Lubrication technology
Area of tribology. This deals with feed of lubricant to friction points or lubrication positions and the application of lubrication equipment.


Inspection, maintenance and repair of equipment and machines.

Martensitic hardening
See Quench hardening

Metal soap
Reaction product from metallic compounds with fatty acids or alkaline soaps. Application as thickener for grease or as EP (extreme pressure) additive for lubricants.

Metal soap grease
Grease containing metallic soap as thickener e.g. with aluminium, calcium, lithium or sodium base.

Mineral oil
Oil derived from crude oil and prepared for use as a lubricant by distillation and refining. Chemical composition mainly hydrocarbons.

Deviation of an actual line from a theoretical ideal line, for example a bearing axis from the shaft axis; may be due to machining, flexing of shaft or deformation of housing.

Misalignment error
Deviation of an actual line from a theoretical ideal line, for example, bearing axis with respect to shaft axis. Caused by machining, shaft deflection or housing deformation.

Mist lubrication
Lubrication method in which a stream of air carries the oil to the friction point. The oil is distributed extremely finely in the air.

Mixed friction
Friction condition where the lubricant film is not complete and the surface peaks of the friction partners may still come into contact

Modal analysis
Modal analysis is a method for investigating the vibration behaviour of machines or machine assemblies in which the machine structure to be investigated is generated as a model in the computer; the machine is excited at a point and the vibration response is measured at corresponding node points in three spatial directions using acceleration sensors; the response spectra are processed by the computer, allowing the vibration behaviour or natural vibration form to be represented on the model.

Molybdenum disulphide MoS2
Grease with a lamellar structure. Under shear stress, the lamellae displace with respect to each other with very low frictional force. The adhesion to metallic surfaces is very strong, the chemical bonding of the Mo and S atoms within the molybdenum disulphide layer gives a high layer strength. The roughness peaks on the metallic surfaces cannot penetrate the molybdenum disulphide layer at it is therefore ideal for dry lubrication and/or as a lubricant for emergency running characteristics or for boundary lubrication.

Surface improvement process (emergency running characteristics) for friction surfaces by molybdenum disulphide. Molybdenum disulphide is held in the roughness of the friction surface. The roughness peaks are plastically deformed with subsequent increase in the load carrying surface. Molybdenum disulphide aids the smoothing process and reduces pick-up.

Monorail guidance system
Linear guidance system comprising guideways and carriages; the designation is determined by the rolling element type: linear roller bearing and guideway assembly or linear ball bearing and guideway assembly

Mounting dimensions
Dimensions such as shaft diameter or hole distances, for example of bearings and guideways, which influence fitting for correct functioning

Movement characteristics
Describe the following in rolling bearings:

  • circumferential speeds and cage and rolling

  • element speed

  • overrolling behaviour for rotary and oscillating

  • movement

  • rolling contact between rolling elements and raceways


Needle roller
See Rolling element

Needle rollers
Cylindrical rolling elements with a high length/diameter ratio (DIN 5402 Part 3)

Neutralization number
Determination of ageing of oils to DIN 51 558 part 1.

Abbreviation for National Lubricating Grease Institute, Kansas City 12, Missouri, USA.

NLGI classes
See Consistency

Nominal contact angle
Angle enclosed by the contact line between the bearing and the radial plane; applies to unloaded bearings, in which the rolling elements are in stress-free contact with the raceways

Nominal viscosity u1
The viscosity dependent on the speed in rolling bearings; determined by the mean bearing diameter and the speed.

Non-locating bearing
Non-locating bearings of the longitudinal, transverse or tilting type permit displacement within the bearing requiring almost no force

Normal load
A load acting vertically on the contact face

Number of rolling elements
The number of rolling elements in one row of a bearing in the direction of movement


O arrangement
Bearing arrangement in which the contact lines are in an O arrangement

Fluid lubricant with a mineral oil and/or synthetic oil base, usually with active ingredients or additives.

Oil change
See Lubricant change

Oil precipitation
Base oil precipitated from greases in bearing arrangements or under mechanical-dynamic strain.

Oil viscosity
See Viscosity

See Poly-a-olefins

One-off lubrication
Lubrication for life. One-off lubrication where the lubricant functions correctly for the life of the component.

Operating clearance
The amount by which the bearing rings in a fitted bearing can be moved in the radial or axial direction from one extreme position to the other.

Operating contact angle
Angle enclosed by the contact line between the loaded bearing and the radial plane

Operating life
See Life, rating

Operating temperature
A measured relubrication interval can be achieved within given limits. The lubricant should be sufficiently thermally stable at the upper operating temperature and should not be too thick at the lower operating temperature.

Operating temperature range
An appropriate lubrication interval is achievable within the specified limits; the lubricant must have sufficient thermal stability at the upper operating temperature and must not become too rigid at the lower operating temperature

Ratio between raceway radius and ball diameter

Oversized groove
See Osculation


Partial lubrication
Lubrication condition in friction points during mixed friction. The friction elements are partially separated by a lubrication film and the surface roughnesses are in partial contact with each other. This usually causes permissible wear.

Prolonged loosening of rolling bearing surfaces which are subject to Hertzian pressure. Based on natural material fatigue or irregularities.

Periodically variable load
Load which varies over time either cyclically or randomly.

See Fatigue

Plastic deformation
See Deformation

Polar characteristics
Improved lubricity, wettability, adhesion and pressure absoprtion of lubricants due to materials. The lubricant is held on the metallic surface electromagnetically due to the polar effect

Synthetic oil based on substances similar to paraffin to which consist only of carbon and water.

Polycarbamide grease
Grease based on synthetic thickener with mineral oil and/or synthetic oil. Preferred application areas: high bearing temperature, long-term and continuous lubrication of rolling bearings, rolling bearings without relubrication facility or with rotating outer ring.

Polyglycol oils
Synthetic oil based on polymers of ethylene oxide and propylene oxide.

Macro molecular bonding as a material, e.g. pour point or viscosity index improver for oils or plastic as thickener for lubricant pastes.

Production process for synthetic oils. Molecules of unsaturated hydrocarbons are extended by heat and catalysts to larger molecules (macro molecules, polymers).

Pour point
Lowest temperature at which an oil still flows freely.
(ISO 3016).

Letter before the designation which indicates a variant of the normal standard design or individual parts

Force due to negative operating clearance or negative bearing clearance in rolling bearings

Preload classes
Differing preload values for stepped increases in rigidity

Press-in force
The force required to assemble parts having an interference fit, for example, to press a drawn cup needle roller bearing into a housing bore

Pressure absorption facility
Ability of a lubricant to reduce wear under pressure loading.

Pressure line
Line connecting contact points of rolling elements and raceways.

See Contact angle

Coatings and layers on metallic materials to prevent damage from corrosion.

pv value
Product of the specific bearing load p and the sliding speed v.


Quality assurance DIN/ISO 9000 and 9004.

See DIN 55 350 part 11 and ISO 8402 for terminology and definitions.

Quench hardening
Quick cooling of a steel, for example in oil or heat bath from martensitic to ambient temperature.


Radial factor X0, X
For combined load, the radial load is multiplied by the factor "X" in order to calculate the equivalent load.

Radial insert ball bearings
Radial ball bearings with extended inner ring and facility for locking on the shaft.

Radial load
A force which acts at an angle of b = 0°.

Influence on the lubricant operating life e.g. from radioactivity. Use of special lubricants recommended.

Recirculating lubrication
Lubrication method in which the lubricant is repeatedly fed into the friction point and is effective.

Reference speed
Bearing-specific feature for defined operating conditions:

  • mean bearing temperatures at outer bearing ring dL = 70°C

  • ambient temperature dA = 20°C

  • load P = 0,005 Co

  • heat flow in bearing seating

  • viscosity of lubricant nB

Reference viscosity
Viscosity for rolling bearings dependent on speed. Determined from the mean bearing diameter and the speed.

Refractive index
Measuring value for identification of a fluid, DIN 51 423 parts 1 and 2.

Regenerated oil
Chemically and mechanically processed old oil. Similar quality to fresh oil is processed correctly.

Relative movement
Movement of at least two reference systems, one of which is regarded as a stationary system.

Relubrication at intervals
Continuous lubrication during which the lubricant is fed to the friction point at specific time intervals.

Relubrication interval
See Lubricant change interval

Removal device
Mechanical, hydraulic, thermal or combination tool for dismantling rolling bearings.

Removal grooves
Recesses for receiving claws and pulling out a bearing using a removal device.

Removal rings (Al/Cu)
Preheated rings or rings heated by induction. These are attached to the inner ring which rapidly expands and can then be withdrawn.

Removal sleeve
Standardized, tapered, split sleeve with groove and thread for fitting and dismantling bearings with a conical bore.

Repair of equipment and machines.

Required operating viscosity n
Determined from the viscosity/temperature diagram for rolling bearings dependent on the operating temperature and the ISO VG at 40°C.

Science dealing with flow and deformation of matter.

Rib friction
Friction between end face of a rolling element and the guide rib

Rib guidance
Guidance of cylindrical rolling elements with parallel axes against a rib

Resistance to displacement under load in the elastic deformation area, dependent on bearing clearance and bearing type

See Deflection

Roller axle bearing
See Wheelset bearing

Roller bearing
See Rolling bearing

Barrel-shaped, tapered or cylindrical rolling elements

Rolling bearing
Ready-to-fit machine element, often defined in standards, for transmitting movements, loads and tilting moments with a high level of efficiency; rolling bearings consist of rolling elements, cages and raceways on rings, guideways or carriages as well as lubricant and, if necessary, seals and accessories

Rolling bearing grease
Grease for rolling bearings to DIN 51 825 part 1 for operating temperature range -20 to 140°C or DIN 51 825 part 2, for low temperatures or DIN 52 825 part 3 for high loads. Standard for high temperature greases is planned.

Rolling bearing rigidity
See Rigidity

Rolling element
Point or rotationally symmetrical bodies for transmitting loads between raceways.

Rolling element design
Basic geometry of a rolling element, for example balls, cylinders or barrels; the detailed design may vary, for example by end profiling or rounded ends

Rolling element friction
See Rolling friction

Rolling element guidance
For cylindrical rolling elements, the parallel alignment of the rolling element axes due to the cage, ribs or enveloping circle; for balls, alignment in the longitudinal slot or groove; for angular contact ball bearings, alignment on the ring with the larger pressure ellipse

Rolling element resistance
See Rolling friction

Rolling friction
1. Rolling friction which is overriden by sliding friction (slippage).

2. Idealized movement friction between bodies in point or line contact whose speeds are equal in magnitude and direction in the contact area and where at least one body rotates about an axis currently in the contact area.

Rolling ratio
Movement ratio between rolling elements and raceways, characterized by the amount of rolling and sliding.

Regular or irregular repeat deviation from an ideal geometric profile.

Roughness depth
Distance to the base profile from the reference profile.

See Mounting dimensions

Rubber interliner
Vibration damping ring e.g. between bearing outer ring and housing.

Running accuracy
Measured in terms of radial runout and axial runout, due to the dimensional and geometrical tolerances of the bearing in motion, defined according to DIN

Running-in lubricant
Lubricant with special ingredients. The ingredients improve the load carrying during running in, smooth the surface and protect against seizing.

Runout friction
Term for friction at the end of movement in friction elements moved with respect to each other.

Corrosion on iron and steel.

Rust film
The beginning of the formation of rust on iron ans steel in the atmosphere.

Rust protection
See Corrosion protection


Abbreviation for Society of Automotive Engineers.

See Striations

Roughing up of the running surface in a rolling bearing due to rolling elements sliding instead of rolling.

Elements such as axial face seal, labyrinth seal, rotary shaft seal or gap seal which prevent the ingress of gaseous, liquid and solid materials through the gaps between combined components during movement or whilst stationary

Seal friction
Occurs in contact between components, expressed in terms of friction coefficient, frictional torque or frictional power

Seal grease
Grease for sealing. Thick consistency with increased sealing effect at labyrinth or gap seals with good wettability and improved sliding for sealing lips such as rotary shaft seals, annular grooves etc.

Sealed bearings
Rolling bearings with fitted seals for protection against lubricant loss and contamination.

See Seals

Elements intended to prevent the ingress of gaseous, fluid and solid materials through the gaps formed by adjacent components whilst stationary or moving.
Operating life

Damage to material surface due to seizing. The damage looks matt and the roughness is considerably greater than that of machined material surfaces.

Semi-locating bearing
Bearing which transmits axial loads from one side and radial loads or axial loads from one side only

Positioning of semi-locating bearings with respect to each other with preload, for example by nut and thread.

Shaft centre displacement
The amount by which a loaded shaft supported by bearings can be displaced from its theoretical position; derived from the bearing clearance and the elastic deformation.

Shaft guidance system
Linear guidance system comprising linear ball bearings or linear ball bearing and housing units combined with shafts or shaft and support rail units

Shear force
Mechanical force which reduces molecules or molecular groups, particularly macro molecules (polymers).

Shear rate
See Speed gradient

Shear stability
Characteristic with respect to viscosity decomposition in non-Newtonian structrually viscous oils.

Sheet metal cage
Metal cage made from, for example, sheet steel or sheet brass.

Silicon oils
Synthetic oil based on semi-organic polymers and copolymers made from silicon/acid units and organic side chains.
See Synthetic oils

Sintered material
Product of powder metallurgy. The metal powders are compressed into an element. The element gains its strength from the sintering process. The materials are classified in accordance with the pore space or the porosity.

Sintered metal plain bearings
Sintered material made from metal powder such as sintered iron, steel, nonferrous heavy metals and light metals.

Powder metallurgy manufacturing process for filters, formed components, bearings. The metal powder is compressed into an element. The element is sintered between 700 und 1200°C. The sintering takes place at a temperature less than the melting point of the metal powder.

Slideway coating
Solid lubricant suspension in a solvent. The slideway coating forms a dry lubricant film. Application areas: dry running, dry lubrication and/or for emergency running characteristics.

Slideway oil
Oil for slideways and sliding guidance systems on machine tools.

Sliding friction
Friction between two bodies moving relative to each other

Reduction in the roughness depth and increase in the load supporting component in friction elements due to relative movement and smearing.

Sodium complex grease
Grease based on sodium complex soap with mineral oil and/or synthetic oil. Preferred application areas: long-term and continuous lubrication for rolling bearings, bearing lubrication at high temperatures.

Sodium soap base grease
Grease base on sodium soap and mineral oil. Emulsified in water therefore not resistant to water. Suitable as gearbox grease for open and closed gearboxes.

Solid body friction
Dry friction with direct contact between friction bodies

Solid lubricant
Solid materials which reduce friction and wear between friction bodies; frequently used solid lubricants are graphite and molybdenum disulphide, solid lubricants also include reaction layers, metal films and thermoplastics such as polytetrafluoroethylene

Solid lubricants
Solid materials which prevent friction and wear between friction elements. Frequently used solid lubricants are graphite and molybdenum disulphide. Other solid lubricants include other reaction layers, metal films and thermoplastics such as polytetrafluoroethylene.

Sort tolerance
Tolerance of a sort; for example, the sort tolerance of needle rollers of class G2 is 2 µm

Subdivision of a quantity according to defined characteristics, for example sorting of needle rollers according to diameter groups

Statistical Process Control

Specific volume
See Density

Speed gradient
Modification in the speed perpendicular to the flow direction i.e. the quotient from the speed and the distance to the flow centre point.

Speed parameter
Permissible speed range (n x dm = speed multiplied by mean bearing diameter) for the lubricant for rolling bearings.

Spherical roller bearing
See Rolling element

Standardization, linear rolling element guidance systems; rolling element guidance systems

DIN 636 Parts 1 to 3
Calculation of basic dynamic and static load ratings

DIN 644 (draft)
Guideways for linear bearings

DIN 645-1 (draft)
Monorail rolling element type guidance systems
Part 1: Dimensions, mounting dimensions

ISO 10205
Linear ball bearings, metric series
ISO 13012
Linear ball bearings, accessories

Starting friction
The friction between frictional bodies as they begin to move in relation to each other

Smoothing of surface roughnesses on new or operational friction components with oil or grease lubrication.

Start-up friction
Term for friction at the start of movement in friction elements moved with respect to each other.

Start-up oil
Start-up lubricant with special ingredients.

Static friction
Friction term for friction elements stationary with respect to each other. The frictional force is grease than the force acting.

Stick-slip effect
Non-uniform movement characterized by alternate adhesion and sliding

Description of the shortest line between two points, often confused with parallelism

See Viscosity

Mechanical, mechanical-thermal, mechanical-chemical or tribological influences acting individually or jointly on a component

Stress spectrum
Part of the tribology system, consisting of friction, friction type and friction condition as well as load, speed and temperature

Linear trace from processing or deeper indentations as a result of mechanical strain. The roughness of the striation is considerably greater than the required roughness.

Structurally viscous fluids
Fluids whose viscosity is dependent on the speed gradient, non-Newtonian fluids or structural viscosity. Non-Newtonian behaviour of lubricants with Newtonian base oils is caused by active ingredients. These active ingredients, such as soaps or polymers, give consistency.

Addition to the designation, consisting of letters and/or numbers, for example, it may indicate variants of a series

Surface layer friction
Friction in which the friction elements are covered with a surface layer either from reaction layers or greases.

Surface protection
See Corrosion protection

Surface tension
Limiting surface tension between a fluid and a gas, usually air.

The effective surface is the surface which separates the object from its surrounding medium.The actual surface is the approximate image from measuring technology of the ideal geometric surface. Note: various measuring processes or measuring conditions (e.g. stylus radius) can give different actual surfaces.The geometric surface is an ideal surface whose nominal form is defined by a drawing or other technical documentation. See DIN 4760 for further details.
Surface protection
Surface tension

Suspensions (additives)
Separation of fluids and solid materials.

Synthetic oils
Oils with particular characteristics produced by synthesis. More stable than mineral oil with respect to heat, oxidation, radiation or other influences.


Thermochemical treatment
Modifies specific chemical composition and characteristics such as corrosion resistance and wear resistance of a material by diffusing in or out one or more elements.

Gives greases their consistency.

Used for:

  • metal soaps for calcium soap base grease, lithium soap

  • base grease, sodim soap base grease

  • complex greases for aluminium complex greases,

  • barium complex base, sodium complex grease

  • synthetic, organic or inorganic thickeners for

  • polycarbamide based greases, gel greases (bentonite,

  • micro-dispersed silicic acids)

The grease has particular characteristics dependent on the thickener.

Thin film friction
Limiting frictional condition with intensive contact of surface roughnesses. A thin lubricant film covers the frictional elements. Wear is very high.

Characteristic of a lubricant to become momentarily softer or thinner due to mechanical action such as stirring or kneading.

Tightening torque
Prescribed screw or nut tightening torque.

Deviation from the normal position due to load or geometrical influence

See Misalignment error

Tilting angle
Angle occurring, for example, by tilting of a ball bearing about the centre of the bearing (larger) or the lowest ball (smaller)

Running accuracy
Dimensional accuracy

Total loss lubrication system
Lubrication method in which the lubricant is effective only once in the friction point.

Track roller linear guidance system
Linear guidance system with track rollers and guideways

Tribological system
Description of a process of wear.

The study of the reciprocal effect of surfaces in relative motion (DIN 50323 Part 1), includes friction, wear and lubrication

Field of tribology. Application of knowledge from friction research, mechanical engineering and industrial management for overcoming friction and wear. The problems are solved with or without the use of lubricants.

Two point contact
Description of the contact relationship in a ball bearing in which the balls have two points of contact with the raceways

Type of operation
Distinction between short-term operation, 8 hour operation and long-term operation.


Ultimate load
Fitted rolling bearings with rings supported by a shaft and a housing, a multiple of the basic static load rating. The ultimate load is given for the outer ring on track rollers.

Useable time
Time period until the disruption of the tribological system.

Used grease
Lubricating grease which is no longer usable or capable of lubrication

Used lubricant
Lubricant which has already been used but which is still capable of performing a lubrication function.

Used oil
Lubricating oil which is no longer usable or capable of lubrication


The toughness of an oil, dependent on temperature and pressure; the viscosity decreases with increasing temperature and increases with increasing pressure; viscosity is the ability of a fluid to resist reciprocal laminar displacement (deformation) of two adjacent layers (DIN 1342, DIN 51550, ISO 3104)

Viscosity classification
Subdivision of fluid industrial lubricants, motor oils or automotive gearbox oils into ISO or SAE viscosity classes.

Viskosity index (VI) = 85; viscosity
Measure of the viscosity/temperature ratio of fluids. ISO 2902


Undesirable change to dimensions and/or surfaces of materials due to frictional forces

Wear mechanism
Physical and chemical processes in which wear occurs.

Wet sump lubrication
Spray lubrication in which the lubricant is taken directly from the sump in the housing and sprayed.

Wetting capability
Ability of a lubricant or corrosion protection agent to spread rapidly and evenly or to penetrate lubrication gaps

Wheelset bearing
Used on rail cars to transfer the forces from the car or bodgie frame to the wheelset and therefore to the rails. Consist of a housing with roller bearings.

Wick oil lubrication
Method of lubrication in which the lubricant is guided to the friction point by means of a wick.

Width series
Initial digit in the dimensional series indicating the width of rolling bearings. Dimensional plans to DIN 616.

Width variation
Variation in width in a single rotation of the ring measured with precision gauge.

Device for cleaning a surface during sliding, in linear bearings, the top surface of the guideway

Working accuracy
See Running accuracy


X arrangement
Semi-locating bearing arrangement with contact lines in an X arrangement




ZB profile
Profile of the outside surface of cylindrical rolling elements characterized by crowned zones between the cylindrical centre and the corners.