ASTM_F_2488_-_05_2013.pdf

Designation:F248805(Reapproved 2013)Standard Terminology forRolling Element Bearings1This standard is issued under the fixed designation F2488;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This terminology covers terms and their definitionsrelevant to the materials and processes associated with rollingelement bearings.2.Terminology2.1 Definitions:absolute viscosity(),n(sometimes called dynamic viscos-ity or just viscosity)a measure of the tendency of the fluidto resist shear.acid number,nmeasure of the quality of a lubricant.Highacid numbers(much higher than the fresh oil)are anindication of lubricant oxidation/degradation.DISCUSSIONOils with high acid numbers should not be used.Acidnumber is measured as milligrams of KOH needed to neutralize 1 g ofoil.additive,nany chemical compound added to a lubricant toimprove or meet special needs necessary for service(formu-lated lubricants).The most important additives areantioxidants,rust,and corrosion inhibitors,and extremepressure(EP)and antiwear(AW)additives.antioxidants(oxidation inhibitors),n chemical compoundsused to improve the oxidation stability and subsequentdeterioration of lubricants.average life(L50),nfor a radial roller bearing,the number ofrevolutions that 50%of a group of bearings will complete orexceed before the first evidence of fatigue develops.DISCUSSIONThe average life maybe as much as five times the ratinglife.ball gage(S),n prescribed small amount by which the lotmean diameter should differ from nominal diameter,thisamount being one of an established series of amounts.DISCUSSIONA ball gage,in combination with the ball grade andnominal ball diameter,should be considered as the most exact ball sizespecification to be used by a customer for ordering purposes.ball gage deviation(S),ndifference between the lot meandiameter and the sum of the nominal diameter and the ballgage.ball grade(G),nspecific combination of dimensional formand surface roughness tolerances.A ball grade is designatedby a grade number followed by the letter“C”indicatingsilicon nitride ceramic.boundary lubrication,ncondition of lubrication in whichthe friction between two surfaces in relative motion isdetermined by the roughness of the surfaces and by theproperties of the lubricant other than viscosity.DISCUSSIONAntiwear and extreme pressure additives reduce thewear of components operating under this regime.case depth,nthickness,measured radially from the surfaceof the hardened case to a point at which carbon content orhardness becomes the same as the ball core.centipoise,nunit of dynamic viscosity.DISCUSSIONThe unit in the cgs system is 1 centipoise(cP).The SIunit of dynamic viscosity is 1 Pa-s and equivalent to 103cP.centistoke,nunit of kinematic viscosity.DISCUSSIONThe unit in the cgs system is 1 centistoke(cSt).The SIunit of kinematic viscosity is 1 m2/s and is equivalent to 106cSpatibility,nmeasure of the ability of a lubricant to bemixed with other lubricants or bearing preservatives(fluidsthat form films on metal surfaces to prevent corrosion duringstorage)to form a uniform mixture without causing anyresultant reaction or precipitation of material.Compatibilityis also a measure of the ability of a lubricant not to cause anydetrimental effect to metal,plastic,or elastomer materials.DISCUSSIONIt is recommended that any preservative material beremoved from bearings before lubrication.contamination,n(1)presence of mostly solid foreign mate-rials like sand,grinding powder,dust,and so forth,in alubricant that might cause an increase in wear,torque,andnoise and result in reduced bearing life;and(2)presence offluids like water,solvents,and other oils that might causeaccelerated oxidation,washout,rusting,or crystallization ofthe additives and other phenomena that reduce a bearingslife.corrosion,ngradual destruction of a metal surface as a resultof chemical attack caused by polar or acidic agents like1This terminology is under the jurisdiction ofASTM Committee F34 on RollingElement Bearings and is the direct responsibility of Subcommittee F34.91 onEditorial and Terminology.Current edition approved May 1,2013.Published May 2013.Originallyapproved in 2005.Last previous edition approved in 2005 as F2488 05.DOI:10.1520/F2488-05R13.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 humidity(water),compoundsformedbylubricantdeterioration,or contaminants from the environment.corrosion inhibitors,ncorrosion inhibitors protect metalsurfaces against corrosion or rust by forming a protectivecoating or by deactivation of corrosive compounds formedduring the operation of a bearing.density,nmass per unit volume of a substance.DISCUSSIONThe cgs unit of density()is 1 g/cm3,and the SI un