>> P.72
■FitTable 4 shows the recommended fit for Shell Type Needle Roller Bearings.As the outer ring is thin, the correct dimensions and Table 5 shows a calculation example of radial clear-accuracy of Shell Type Needle Roller Bearings are ance after tting. This calculation applies to bearings obtained only after they have been press-fitted into without inner ring to be tted into rigid steel or cast the housing bore. Bearing accuracy is directly affect-iron housings. When the housing is made of light ed by housing dimensions, shape and rigidity. This alloy or a thin steel pipe, it is necessary to check should be taken into account when considering t and dimensions by actual measurement.accuracy. The radial clearance after tting the bear-Generally, when making the radial clearance smaller, ing to the shaft and the housing bore varies with their it is recommended that the shaft diameter be tolerances.increased, without decreasing the housing bore diam-eter.Table 4 Recommended fit Type of bearingHousing materialShaft (1)Without inner ringWith inner ringTolerance classTA … Z,BA … Z,BHA … Z, TAM,BAM,BHAM,YT,YB,YBH TLA … Z,TLAM,YTL, TLA … UUSteelCast ironLight alloy(Thin steel pipe)SteelCast ironLight alloy(Thin steel pipe)h6h6h6h6k5(j5)k5(j5)k5(j5)k5(j5)Housing boreJ7M7(N7)N7R7(S7)Note(1) hen housings are made of light alloy or a thin steel pipe, the roller set bore diameter is greatly affected by the housing thickness and to conrm the amount of dimensional Therefore, before mass-production assembly, assembly tests should be carried out shape. change and to determine the tolerance of the shaft which will give normal clearances.Calculation procedureExample of TLA 2020 Z Dimension of roller set bore diameter of bearing after it has been press-fitted into the ring gauge.1 Dimension of ring gauge (D0): See Tables 2.1 and 2.2 on page B4. Max. value of roller set bore dia. (Fw max): No-go dimension of plug gauge Min. value of roller set bore dia. (Fw min): Go dimension of plug gaugeFrom Table 2.1 on page B4=25.972D0 Fw max =20.028Fw min =20.007 Dimension of housing bore2 Max. value of housing bore (Dmax): See the dimension table. Min. value of housing bore (Dmin): See the dimension table.From the dimension table on page B14, Dmax=25.993Dmin =25.972DFw Dimension of roller set bore diameter of bearing after it has been press-fitted into the housing bore3 Max. value of roller set bore dia.(Fwe max)=(Dmax-D0) +Fw max Min. value of roller set bore dia.(Fwe min)=(Dmin-D0) +Fw minFrom the equations,Fwe max=20.049Fwe min =20.007rGF Dimension of shaft Max. value of shaft dia. (Fmax): See the dimension table. Min. value of shaft dia. (Fmin ): See the dimension table. Radial clearance after mounting5 Max. value of radial clearance(Gr max)=Fwe max-Fmin Min. value of radial clearance(Gr min)=Fwe min-Fmax From the dimension table on page B14,Fmax =20.000Fmin =19.987From the equations, Gr max =0.062 Gr min =0.007 The radial clearance after mounting becomes 0.007~0.062 mm.D Fw F Gr :Housing bore diameter:Roller set bore diameter:Shaft diameter:Radial clearanceTable 5 Calculation example of radial clearance after fittingunit: mmB5
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