Originally Posted by 11.4

This has been covered before, but NJS hubs (and equivalent hubs in other drillings) are actually manufactured by a technique called metalspinning. A blank is put in a metalworking lathe and spun rapidly. A relatively dull tool is then pushed against it and causes the metal to flow gradually to form the shape of the hub, much like one would push clay into shape while spinning on a potter's wheel. You typically make a separate blank for each side and then put them together and use spinning to fuse the two halves together. You will occasionally see signs of this fusion joint at the centerline of the hub..