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On Design Cooling Fit and Press Fitting ¡Cooling fit There are two methods to set Oiles bearings into a housing. One is called press-fitting. For press fitting, a mandrel and a press machine are used. The other is called cooling fit. The cooling fit uses liquid nitrogen or dry ice. Compared to press-fitting, cooling fit is efficient and achieves more accurate installation. Avoid shrink fitting as it may deteriorate bearing function. ¡Cooling fit procedure 1. Equipment and materials œRefrigerant : liquid nitrogen, dry ice œContainer : A chamber covered with heat insulator which is large enough to accommodate bushings 2. Calculation of amount of shrinkage of outer diameter of bearing caused by cooling(¢D) @œWhere outer diameter of bearing : D @œWhere coefficient of thermal expansion of bearing :ƒ¿ @œWhere atmospheric temperature : T0 @œWhere cooling temperature : T1 @@¢D à D ~ ƒ¿ ~ i T0 | T1 j @Thermal expansion of Oiles 500SP Fƒ¿ 2.2 ~ 10|5/Ž @Thermal expansion of Oiles 500B Fƒ¿ 1.8 ~ 10|5/Ž @Thermal expansion of Oiles 500F F ƒ¿ 1.2 ~ 10|5/Ž @¦For other materials, please refer to the mechanical properties of each product. @Example : Material Oiles 500B 100 I.D. ~ 130 O.D. ~ 100 L @@By cooling, temperature goes down to |70 Ž from 20 Ž @@¢D  130 ~ 1.8 ~ 10|5 ~i20 |i|70jj 0.211mm @@¦For the bearing whose diameter exceeds ƒÓ500 mm, consult an Oiles representative. 3. Operation procedure 1. As a cooling agent, use liquid nitrogen or dry ice. The standard cooling temperature is |40 Ž to |70 Ž. 2. Cooling time should be more than one hour. Cooling time needs to be longer if the interference is larger, depending on applicable fitting tolerance. In addition to the cooling fit, press fitting should be used if cooling time needs to be shortened. 3. Measure and confirm outer diameter of the bushing and inner diameter of the housing before cooling. If any defect is found during fitting, it may develop into a major trouble. 4. Bushing should be inserted into the housing soon after taking it out from the cooling agent in a chamber. If stopped during fitting, dimension of the busing goes back to its original size and it is extremely difficult to withdraw the bushing from the housing and do the fitting again. 5. Apply lubricant onto the sliding surface. Note : Warm housing up to 20 Ž to 30 Ž if sufficient temperature gap could not be maintained as in winter. 341Selection Guide Product Air Bearings Metallic Bearing Multi-layer Bearing Plastic Bearing Information Technical Corporate Profi le Information Slide Shifter