The pivot tube is swaged together after installing the stack on the mirror head. When the head turns, it applies side force to the balls, and some corner force to the top plate. The 3 spring washers above the plate hold pressure on the balls, and the one below holds the plastic mirror head against the black steel plate, which has holes for the balls to rest in, creating the detent positions.

Owner caption April 2012 · Photo 4356 of 5000