ENGINEERING FOR THIN SECTION BALL BEARINGS

1 For more information visit our web site at FOR thin SECTION ball BEARINGS93 thin SECTION ball BEARINGS 2008 RBC BEARINGS Incorporated. All rights SECTIONBEARINGSTHIN SECTION ball bearing ENGINEERING DATAThe methods, equations, and technical datapresented in this SECTION allow the user to select thecorrect BEARINGS and estimate their performance for awide range of applications. For applications with severeor unusual operating conditions, RBC is prepared toprovide an in-depth analysis and recommend the mostsuitable bearing standard BEARINGS cannot be used, RBC canmeet the application requirements with a specialbearing design specifically tailored for optimumperformance. Questions concerning information in thissection should be directed to the appropriate RBCA erospace BEARINGS sales and Fatigue Life of ball BEARINGS The basic dynamic radial load rating, C, or dynamiccapacity, for a ball bearing is the calculated, constantradial load at which 90% of a group of apparentlyidentical BEARINGS with stationary outer rings canstatistically endure 106revolutions of the inner Standard 9 with correction factors for racecurvatures was used to calculate the catalog dynamic thrust and dynamic moment loadratings are also shown in the product tables.

2 Theratings shown are a guide for the maximum loadsunder which these BEARINGS should be operated witheither pure thrust or pure moment loading. Thrustratings are to times the radial ratingsdepending on the bearing type and load ratings are not additive. For combined radialand thrust loads, an equivalent radial load is to basic static load rating, Co, or static capacity, is that uniformly distributed load, which produces amaximum theoretical contact stress of 609,000 psi. Atthis contact stress, permanent deformation of ball andraceway occurs. This deformation is of the ball = number of ballsd = diameter of balls (in.)The rating life, L10, is a statistical measure of the lifewhich 90% of a large group of apparently identical ballbearings will achieve or exceed. For a single bearing ,L10also refers to the life associated with 90%reliability.

3 Median life, L50, is the life that 50% of thegroup of ball BEARINGS will achieve or exceed. Medianlife is approximately five times the rating relationship between rating life, load rating, andload is:L10= (C/P)3with L10= rating life (106rev) C = basic dynamic radial load rating (lbf) P = equivalent radial load (lbf)To obtain the rating life in hours, use:L10 hrs= 16667/N * (C/P)3with N = speed (rpm) The equivalent radial load is defined as:P = XFr+ YFawith Fr= radial load (lbf) Fa= axial load (lbf) X - see below Y - see below Radial Contact bearing Calculations For radial contact BEARINGS calculate P with X = 1 and Y = 0. Then recalculate P with X = and Y = (see chart below).Use the larger value of P to determine more information visit our web site at FOR thin SECTION ball BEARINGS94 thin SECTION ball BEARINGS 2008 RBC BEARINGS Incorporated. All rights or 4-Point Contact BearingCalculations* For angular contact and 4-point contact bearingscalculate P with X = and Y = 0.

4 Then recalculate Pwith X = and Y = Use the larger value of P todetermine equations are valid in the range ofapproximately 100 hrs to 100,000 hrs of life. Extremeloads or speeds may result in a shorter life; while inless demanding applications, metal fatigue may neveraffect bearing service life.*Capacity and fatigue life information is based on ANSI/ABMA Standard 9-1990 published by:The American bearing Manufacturers Association, Inc., 1200 19th Street, NW, Suite 300, Washington,DC 20036-2401 Adjustment Factors for Rating Life If a bearing design and operation deviatessignificantly from normal, it may be necessary to useadditional factors to estimate the fatigue life a1*a2*a3*L10hrswith a1= reliability factor a2= material and processing factor a3= application factor Reliability Factor a1 Reliability is the percentage of a group of apparentlyidentical ball BEARINGS that is expected to attain orexceed a specified life. For an individual bearing it isthe probability that the bearing will attain or exceed aspecified life.

5 Typical bearing fatigue life is calculatedfor 90% reliability. The life adjustment factors for otherreliability numbers are shown %LnReliability Factor a190 95 96 97 98 99 Factor a2 For standard BEARINGS , the material factor a2is equalto Factor a2is determined by material processing,forming methods, heat treatment, and other manufac-turing methods. Some commonly used material factorsare listed below:Application Factor a3 The application factor a3 is equal to for mostapplications. Unusual or extreme conditions in certainapplications such as low speed, shock loading,vibration, and extreme temperature may lower theapplication factor to Contact your RBC AerospaceSales Engineer for help in determining this factor forspecial and Speed Limitations The load ratings shown in the product tables are notadditive.

6 For combined simultaneous loading, anequivalent radial or thrust load must be considered. Ingeneral, C-Type BEARINGS are designed for radial loadingapplications; moderate thrust and/or moment loadingmay be applied in combination with radial loading. Forthrust loading applications use the A-Type bearing ; anyradial loading should only be applied in combinationwith thrust loading. X-Type BEARINGS are primarily forreversing thrust and moment loading, pure radialloading should not be limiting speeds shown in the product tables arebased on standard lubrication. The unsealed bearingspeeds are calculated assuming the BEARINGS arelubricated with MIL-PRF-8085. Limiting speeds forsealed BEARINGS are calculated assuming the bearingsare lubricated with MIL-PRF-23827 grease. If bearingsare lubricated with alternate oils or greases, newlimiting speeds must be calculated, see page , Conditiona2max52100, Air melt 52100, Vacuum degassed 52100, Air melt and TDC Plate 52100, Vacuum melt, (CEVM) 440C, Air melt 440C, Vacuum melt (CEVM) M50, Vacuum melt (CEVM) M50, Vacuum re-melt (VIM-VAR) more information visit our web site at FOR thin SECTION ball BEARINGS95 thin SECTION ball BEARINGSOPERATING CONDITIONSL ubricationLubricants serve a number of very importantpurposes in ball BEARINGS , including: protecting bearing surfaces from corrosion reducing rolling and sliding friction preventing metal-to-metal contact between ballsand raceway providing a barrier against external contaminants(grease) removing heat (oil)Lack of lubrication or inadequate lubrication is themost common cause of bearing RBC thin SECTION ball BEARINGS are lubricatedwith either oil or grease.

7 The unsealed BEARINGS , the Kseries, are thoroughly coated in MIL-PRF-8085 oil anddrained of excess. Sealed BEARINGS are lubricated withMIL-PRF-23827 grease. The external surfaces of sealedbearings are lightly coated with the same grease forcorrosion resistance. Additional lubricants are alsoavailable. An RBC Aerospace Sales Engineer can helpselect the appropriate lubricant for special Standard RBC thin SECTION ball BEARINGS can operateat temperatures from -65 F to +250 F. Temperatures upto 350 F can be reached if the BEARINGS are temperaturestabilized. By the use of special materials RBC can provide BEARINGS for operation to 900 F. Contact theRBC Aerospace BEARINGS sales engineer for recommen-dations on BEARINGS operating above 250 Speed The limiting speed of a bearing is dependent upon anumber of different factors including bearing size, bearing type, ball separator design, lubrication andloading. The limiting speeds for the BEARINGS shown inthis catalog are determined using the following:N = with N = Speed (RPM) E = ( bearing pitch diameter) k = constant, see table below D+B21000 *k EThe k values shown give the maximum speeds atwhich a typical thin SECTION ball bearing can operate.

8 Itis recommended that operating speeds of largediameter BEARINGS in a given series be reduced up to40% of the calculated rating to avoid high bearingtemperatures. Speed ratings can also be impacted byload conditions, lubrication, alignment, and ambienttemperature. All of these factors must be consideredwhen designing thin SECTION ball BEARINGS into PAIRS AND AXIAL PRE-LOADING Duplex Pairs Duplex BEARINGS are a pair of angular contact RBCthin SECTION ball BEARINGS specially ground for use as amatched set. A duplexed pair can be used to provideaccurate shaft location, to increase capacity or toincrease stiffness of the bearing assembly. A duplexpair of RBC thin SECTION ball BEARINGS is ground so thatwhen mounted using recommended fits, there will beno internal clearance in the BEARINGS . There are threebasic mounting methods to accommodate differentloading requirements: Back-to-Back (DB), B-Type Face-to-Face (DF), F-Type Tandem (DT), T-Type k ValueBearing TypeLoad ConditionGreaseOil C or ARadial or Thrust1620 XThrust1012 XRadial, Combined34 Radial & Thrust, or Moment Heavy radial loads Combined thrust and radial loads Reversing thrust loads Excellent rigidity Moment loads Back-to-Back, DB B-Type 2008 RBC BEARINGS Incorporated.

9 All rights more information visit our web site at FOR thin SECTION ball BEARINGS96 thin SECTION ball BEARINGS 2008 RBC BEARINGS Incorporated. All rights PlayRadial play (diametral clearance) is the distance theinner ring can be moved radially from one extreme positionto the other. Standard RBC thin SECTION ball BEARINGS aremanufactured with enough radial play that some clearanceremains after the bearing is properly there is negative radial play (diametral pre-load) there is interference rather than clearancebetween the balls and the races. As the interferenceincreases, the friction, stiffness and torque alsoincrease. RBC thin SECTION ball BEARINGS can bemanufactured with customer specified diametral pre-load or clearance. Consult an RBC Aerospace Bearingssales engineer for design and Axial Runout Radial runout of RBC thin SECTION ball BEARINGS is ameasurement of the thickness variation of the bearingrings. The outer ring is measured from the ball path tothe outer diameter of the ring, the inner ring is measuredfrom the ball path to the bore.

10 Radial runout is defined asthe wall thickness variation of the rotating runout is measured from the ball path to theface of the bearing rings. The variation in thicknessmeasured is the axial Precision Grades RBC thin SECTION ball BEARINGS are available in fourprecision grades. RBC precision classes 0, 3, 4, and 6correspond to ABMA ABEC grades 1F, 3F, 5F, and 7 Frespectively. The tolerances for the bearing bores, outerdiameters, radial runouts, axial runouts, and radial playsare shown in the Tolerance Tables on pages 102 and Housing Fits Proper shaft and housing fits are critical to thesuccessful operation of a thin SECTION ball internal clearance of the bearing will be reducedproportionally by an interference fit. In addition, theroundness of the shaft and housing will directly affectthe roundness of the inner and outer ring most applications, the inner ring is rotating and the load is stationary with respect to the outer this circumstance, a light press fit onto the shaft isrecommended.