I aim to build a system of a steel flat bar rotating around a pivot point with the help of a couple of dc motors mounted on the edges of the bar. After doing some search I decided to build it using a steel punched bar, a steel axle hollow shaft as the rotational axis and a couple of rotating gears to mount a potentiometer in order to take measurements. My issue is how to connect the flat bar with the hollow shaft in order to enable the bar to rotate around this point. What component should I consider ? I suppose that the hollow shaft should go through this component and then this component should be connected to the flat bar using some screws perhaps.