How are ball bearings machined?

There are four parts to a standard ball bearing, which include the outer race, the rolling balls, the inner race, and the cage. The process starts with steel tubing of an appropriate size where Automatic machines use cutting tools to cut the basic shape of the race, leaving all of the dimensions slightly too large. The rough cut races are then put into a heat treating furnace, dipped into an oil bath to cool them and make them very hard and after the heat treatment process, the races are ready for finishing. The balls, which start out as thick wire goes through a process called cold heading and are then put between the faces of two cast iron disks, where they ride in grooves. The balls then go through the heat treatment process, similar to that used for the races, later moved to a lapping machine. The steel cages are stamped out of thin sheet metal, bent to their final shape in a die and the plastic cages are made by a process called injection moulding. The final step is the assembling of all these four parts to make one device.