The reason a cylindrical grinder can grind a smooth mirror finish onto all sides of a metal shaft is because of the way it is designed. The bed looks like that of a lathe. The bar to be ground is supported on centers between a head and tail stock. The head stock is motorized and rotates the bar continuously. The bed also sits on a set of linear guide rails. Underneath the bed a long hydraulic piston moves the bed side to side in a linear reciprocating motion. A grinding head with a rotating stone positioned at a 90 degree angle to the bar is indexed in by thousandths of an inch to grind smooth the surface of the bar as it is passed back and forth across the face of the stone as it is being rotated by the motorized head stock. My boss told me how each part of the machine functions, and from that I designed and built a new electric system for it. I also rebuilt the hydraulic system too adding a new pump and valves. After I was done the machine ran perfectly and the customer was very happy with it. I was happy because I had just built my very first complete industrial electric control system on my own from scratch. I had fun and my work was appreciated. From this point on I got to do even more interesting projects.