Published on March 15, 2017
The ball has cylindrical portion diameter of which is slightly smaller than diameter of the socket surface hole (the circle on upper surface of the outer part). Assembling position: axis of the said cylindrical portion is perpendicular to the upper surface of the socket. The ball can not come out of the socket for other positions because the ball diameter is larger than diameter of the socket surface hole.
STEP files of this video:
