small size bearings are generally passed on to the shaft whereas large size bearings are heated in an oil bath ( around 80 degree c.) for easy placement of a bearing on to the shaft. you needs these in your life. i can't believe that this will be my 20th year teaching! there are plenty of ideas and activities out there to choose from, but the costs can start adding up rapidly. i would love to hear your feedback on this. step one is to call us today by dialing 888-592-7779 to begin your project. 