This is an aluminum casting that is machined by holding on the outer diameter first, and machining the back of the casting so that the chuck-jaw will hold onto the back inside of the casting. The front of the casting can be machined to size. Next, the casting is placed in a fixture and holes are drilled to tolerance.
After the machining, drilling, and deburring are done, the casting can then be placed on the studs of an axle of a semi-truck. The nuts can be secured with a wrench.
Drawing #1 is the front view of the casting after complete machining.
Drawing #2 is the side view if casting was cut in half.
Drawing #3 is the back view of casting after finish machining.