>> P.48
Raceway materials and heat treatmentDimensions related to mounting of bearingsWhen using shafts and housings as raceways, the fol-The dimensions of shaft and housing related to lowing materials are generally used.High-carbon chromium bearing steelmounting of the needle roller bearings are shown in the table of dimensions for each bearing. (See Fig. SUJ2 JIS G 480513.)Carburizing steel SCM415〜421 JIS G 4053Carburizing steel SNCM 220 Carburizing steel SCr 420 JIS G 4053JIS G 4053Carburizing steel SNC 415, 815 JIS G 4053Carburizing steel S 15 CK JIS G 4051In addition, S50C and S55C (JIS G 4051) can be used after through hardening or induction hardening.The hardened layer produced by tempering at +160〜+180°C after hardening must have a ne uniform martensite microstructure.When hardening the raceway surface by case hard-ening or induction hardening, a surface hardness of 58〜64HRC and an appropriate thickness of the hardened layer must be ensured. The minimum effective thickness of the hardened layer after heat treatment and grinding is dened as the distance from the surface to the depth where the hardness is 550HV, and it is obtained by the following equation.Eht≧0.8Dw(0.1+0.002Dw)……………(36)where,Eht: Minimum effective thickness of the hardened layer, mmThe minimum value of the shaft shoulder diameter da which receives the inner ring, and the maximum value of the housing shoulder diameter Da which receives the outer ring, represent the effective shoulder diame-ters (excluding the chamfered part) which make prop-er contact with the side faces of the inner and outer rings respectively.Also, the maximum value of the shaft shoulder (or inner ring retaining piece) diameter da is the dimen-sion related to the ease of mounting/dismounting of the shaft and inner ring to/from the housing and outer ring.The largest permissible single corner radius ras max of the shaft and housing must be smaller than the small-est permissible single chamfer dimension rs min of the bearing so that the side surface of the bearing can make proper contact with the shoulder. Table 28 shows the related dimensions.For dimensions of the fillet relief when finishing the shaft or housing by grinding, the values shown in Table 29 are recommended.For other dimensions related to mounting, see the related section for each bearing as required.In addition, for ease in dismounting of bearings, it is the convenient to make notches in the shoulder of the shaft or housing to allow the insertion of dismounting hooks.DadaFig. 13 Dimensions related to mounting Dw:Roller diameter, mmGenerally, the required effective thickness of hardened layer is at least 0.3 mm.A45
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