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Determine the bearing dimensions
 
    In many cases, the size of the bearing bore has been specifically defined by the structure of the machine or device . Whether working life, static load safety factor and whether the economy will meet the requirements, bearing the rest before the final selection of the size and structure of the form , must undergo size calculations. The calculation includes the actual load with its load bearing capacity for comparison. Rolling refers to the static load after load bearing is stationary ( no relative movement between the inner and outer rings ) or rotation speed is very low . In this case , the calculation and the rolling body raceway and the safety factor of excessive plastic deformation . Most affected by dynamic load bearing inner and outer rings relative motion , check the size of calculus raceway safety factor and fatigue damage early rolling . Only in special circumstances , only in accordance with DIN ISO 281 up to the actual working life doing in the name of life calculus . To focus on the economic performance of the designs , to take full advantage of the bearing capacity as possible. To more fully utilize bearings , then the more important for the choice of bearing size calculation accuracy.

    Static load bearing
 
    Calculate the static load safety factor Fs help determine whether the selected bearings have sufficient static load rating . FS = CO / PO where static load safety factor FS , CO rated static load [KN], PO equivalent static load [KN] static load safety factor FS is to prevent rolling parts contact zone safety factor permanent deformation occurs . To be smooth, ultra-low noise bearings , requires a high value of FS ; requires only moderate running noise of the occasion , the choice of a small number of FS; generally recommend using the following values ??: FS = 1.5 ~ 2.5 for low noise level of FS = 1.0 to 1.5 applied to conventional noise level FS = 0.7 ~ 1.0 for medium noise level rated static load CO [KN] have been listed in the table for each different specifications of the bearings. The load ( on the radial bearing is a radial force , in terms of the thrust bearing is the axial force ) , the theoretical pressure at the center of the rolling element and raceway contact area is generated : -4600 N/MM2 self-aligning other types of ball bearings -4200 N/MM2 ball bearings -4000 N/MM2 all roller bearings under the action of a static load rating of CO , the maximum load parts of the rolling elements and raceway contact area , the resulting total plastic deformation about ten-thousandth the diameter of the rolling elements . Equivalent static load PO [KN] is a theoretical value for the purposes of the radial bearing is a radial force , in terms of axial thrust bearing and solidarity . PO maximum stress in the rolling bearing raceway contact with regional centers and arising , in combination with the actual load was produced by the same stress . PO = XO * F r + Ys * Fa [KN] where PO equivalent static load , Fr radial load , Fa axial load units are kN , XO radial coefficient , YO axial coefficient .

    Dynamic load bearing

    Basic dynamic load bearing standard calculation method specified in DIN ISO 281 is material fatigue failure ( appears pits ) , life expectancy is calculated as follows : L10 = L = (C / P) P [106 rpm ] where L10 = L nominal rated life [ 106 rpm ] C dynamic load [KN] P equivalent dynamic load [KN] P L10 life index is converted to 1,000,000 units in the name of the rated life [ 106 rpm ] C dynamic load [KN] P index L10 life is 1000000 rev nominal rated life . For a large group for the same type of bearing , which should reach or exceed 90% of the value. Dynamic load rating C [KN] can be found in each type of the parameter table bearing , in the role of the load , the rated life of the bearing can reach 1 million revolutions . Equivalent dynamic load P [KN] is a theoretical value for the purposes of the radial bearing is a radial force on the thrust bearing is axial force. Its orientation, size constant. The same as the actual load bearing life combined effect equivalent dynamic load under the action . P = X * Fr + Y * Fa where: P equivalent dynamic load , Fr radial load , Fa axial load units are kN , X radial coefficient , Y axis coefficient . Different types of bearings X, Y value and the equivalent dynamic load calculation basis can be found in the form of various types of bearings and foreword . Ball bearings and roller bearing life index P is different. Ball bearings , P = 3 pairs of rollers bearings , P = 10/3

Variable load and variable speed

    If the value of the bearing load and speed changes with time , then calculating the corresponding equivalent load must be considered . Continuous load and speed curve should be replaced with a piecewise approximation . Equivalent dynamic load calculation becomes:

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    Minimum load of rolling bearings
 
    Too small a load coupled with lack of lubrication will cause rolling slippery , leading to bearing damage. The minimum cage bearing load factor P / C = 0.02, while the minimum load factor full complement bearings P / C = 0.04 (P for the equivalent dynamic load , C is the dynamic load rating )

    Bearing accuracy and level
 
    Rolling accuracy of ( mainly ) the dimensional accuracy and rotational accuracy. Accuracy has been standardized into P0 level , P6 class , P5 level , P4 level , P2 level five grades.
   
    In order to improve accuracy from 0 from 0 for general purposes is sufficient , but in the conditions shown in Table 1 for the occasion or need 5 or higher accuracy.
 
    Although based on the above level of accuracy as a benchmark developed by the ISO standard , but its title is different in each country standards .
    Table 2 lists the comparison of various types of bearings and precision grade applicable standards between countries . Dimensional accuracy ( installed with the shaft and housing -related projects )
    1 , the inner diameter , outer diameter , width, and the width of the assembly tolerance
    2 , the roller diameter and complex set of allowed outside diameter deviation complex
    3 , chamfer dimensions allowable limit value
    4, the width of the fluctuation amount of allowable rotation accuracy ( jitter associated with the rotating body project )
     1 , the inner and outer radial runout and axial runout allowed
     2 , to allow the inner lateral runout
     3 , the outer diameter surface of the allowable amount of change in inclination
     4 , the thickness of the thrust bearing raceways allow movements
     5 , tapered bore tolerances and allow movements