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Usually, Oiles bearings are press-fitted into the housing. For this procedure, a mandrel and a press machine are used. In case of a metallic bearing with large press fitting interference, chamfer outer diameter of the bearing and inner diameter of the housing. Then use a mandrel to facilitate easier press fitting. ■Press fitting procedure : Calculation of press fit force When a bushing is press fitted into a housing with some interference, the bushing I.D. becomes smaller than the original size. Amount of this inner diameter change depends on the dimension of the housing, the bushing (thickness and shape), and the material.Testing by dimension and by material is required in order to determine precise change. However, it is not feasible to conduct tests for all the combinations of materials and dimensions. Therefore amount of inner diameter change is determined based on the below formula. Load Mandrel Bushing Chamfer Housing Bushing Housing σn σb P φd φD tb Stress distribution of cylindrical combination Vb tb Eb D Vh Eh Dh P Kb Kh F Lμ S △d : Poisson's ratio of bushing( refer to table 1) : Wall thickness of bushing( mm) : Young's modulus of bushing( kgf/mm2()refer to table 1) : Outer diameter of bushing=Inner diameter of housing( mm) : Poisson's ratio of housing(refer to table 1) : Young's modulus of housing( kgf/mm2()refer to table 1) : Outer diameter of housing( mm) : Pressure in radius direction at the boundary generated by interference( kgf/mm2) : Coefficient of combined sleeves( kgf/mm2()for bushing) : Coefficient of combined sleeves( kgf/mm2()for housing) : Press fit force of bushing( kgf) : Length of bushing( mm) : Coefficient of friction between bushing and housing( refer to table 2) : Interference of bushing against housing( mm) : Amount of inner diameter change of bushing after press fit( mm)(amount of shrinkage) Poisson's ratio 0.30 0.30 0.12 0.05 0.30 0.30 0.28 0.31 0.25 0.25 Young's modulus(kgf/mm2) 21,000 16,500 to 18,000 5,000 2,400 11,000 to 13,000 21,000 19,700 20,400 10,500 9,450 SS400 FCD 450 to 500 Cermet M Cermet G FC 250 SCM 440 SUS 304 SUS 420J2 CAC403 (BC3) CAC406 (BC6) Material Table-1 Poisson's ratio and Young's modulus Poisson's ratio 0.32 0.35 0.25 0.35 0.32 0.30 0.25 0.17 0.20 0.35 Young's modulus(kgf/mm2) 12,000 11,000 6,600 7,700 8,400 21,000 6,000 700 1,800 to 3,000 288 CAC703 CAC304 500B 500SP 500AB 2000 300 250-07 Fiberflon 80 Material Meallic bushing vs. metallic housing Plastic bushing vs. metalic housing Plastic bushing and plastic housing 0.20 0.15 0.15 Table-2 Coefficient of friection between bushing and housing Kb= {(Eb・4tb)/D}・(1−tb/D) (1−Vb)+(1+Vb)・(1−2tb/D)2 Kh= Eh・{(Dh/D)2 −1} (1−Vh)+(1+Vh)・(Dh/D)2 P = ・ D S Kb+Kh 1 ●Amount of inner diameter change △d of bushing after press fit △d= = 2Eb・tb P・D2 2Eb・tb・(Kb+Kh) S・D ●Press fit force of bushing F = π・P・D・L・μ Dh ■Press fitting 342 Selection Guide Product Information Plastic Bearing Multi-layer Bearing Metallic Bearing Air Bearings Technical Slide Shifter Information Corporate Profi le Technical Information