A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races.
The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads.It achieves this by using at least two races to contain the balls and transmit the loads through the balls. In most applications, one race is stationary and the other is attached to the rotating assembly.Because the balls are rolling they have a much lower coefficient of friction than if two flat surfaces were sliding against each other. Although bearings had been developed since ancient times,now we use it to make the folding knife to keep its blade opening and closing easily and smoothly.Its core technology to make a ball bearing knife is not what material we use but how to make its blade in the middle of the frame and to pass 100 thousands opening and closing test. If a ball bearing passed this test, its blade would still open and close in good power.To make a good ball bearing folder, We will mill a pocket in the blade or both in its frame assembling with a steel ball bearing or ceramic according to its design to keep it working smoothly.