2. The rough cut races are put into a heat treating furnace atabout 1,550 degrees Fahrenheit (843 degrees Celsius) for up toseveral hours (depending on the size of the parts), then dipped into an oilbath to cool them and make them very hard. This hardening also makes thembrittle, so the next step is to temper them. This is done by heating them in asecond oven to about 300 degrees Fahrenheit (148.8 degrees Celsius), and thenletting them cool in air. This whole heat treatment process makes parts whichare both hard and tough.
3. After the heat treatment process, the races are ready for finishing.However, the races are now too hard to cut with cutting tools, so the rest ofthe work must be done with grinding wheels. At this point, the races arefinished, and ready to be put together with the balls.