How Ball Bearings Are Made

By Author: Jian Han
Total Articles: 6
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A normal ball bearing consists of four main parts. Firstly races manufacture through a process which is initiated by making steel tubes of exact size, by cutting the basic shape to some extent large in entire dimensions. The reason to keep them huge is that before finishing, the races will be heat-treated. Initially, the rolling balls have a thick shape and after passing by a cold bearing, the process resulted balls look like a Saturn planet having a ring in the middle which is known as a flash.

After the cooling process, the irregular cut races are passed through a furnace for heating treatment on 843 °Celsius for numerous hours, then for cooling, these are placed inside an oil bath after which they become very hard. These races may become weak due to this hardening; therefore, to protect them from weakening they are passed through a second oven on 148.8 °celsius and after that, they are cooled in the air. This process of heating will make up parts that are both tough and hard. After the heating process, the next step is finishing. Tough races are put in grinding wheels to get proper and very smooth finished surface ...
... which should be round with flat sides. After grinding, the surface is lapped by an abrasive slurry, which is used for polishing the races for numerous hours which results in a mirror finish. At this time, finishing is completed and the races can be kept with the balls.

The next step is to make the balls quite small by cutting them in the automatic machine; the machine mould the wires to form a ball shape. During this process, around the balls there is an excess metal ring which is still left called a flash. Then the balls are passed from a machine for removing this flash. These balls are rotated between two rill plates in which one of rill plate spins and the other is stationary. There are grooves inside the rill plates to provide the guidance to balls in a rounded path. After removing the flash, the balls are then passed into a heating process which makes them harden. And then these balls go through a process of grinding. Lapping is the last process where similar machines are required; these machines make the ball into a perfect glittery finish by exerting less pressure and the size remains the same during this process.

The last part of ball bearing is the cage. Two types of cages are used in which one of them is steel and other is plastic. The process which is used to make the cages is known as injection molding. During this process, metal plastic is squirted into the cage which fills the empty metal molding as well as allows them to harden. Now the cage is finished and available for assembly. All four parts are finished, now it's time to put together all parts in bearings. Firstly, the interior race is placed within the exterior race. The balls are inserted between the races and cages are used for holding the balls away from one another. Now the bearing is assembled with a protective coating and it is wrapped up for shipping. Inspection is the last step of the process. Proper machinery is used to measure the balls to see if they meet the expected tolerance.