Watching engine parts get machined is always cool, but some of the machining operations are way cooler than others. Decking a block is pretty mundane, and so is boring and honing, even though there is a lot of movement going on. Line boring isn’t all that exciting looking either, but the boring bar is pretty big so that makes it look more impressive for sure. Grinding crankshafts on the other hand is one of those processes that can make your brain hurt because there are multiple “axis” that the crank must spin around in order to grind it. Each rod journal is its own axis and so are the mains. That means that depending on which journal you are grinding, the crankshaft could be spinning in what looks like a horribly wobbly manner.
If you were to mount the crank into the machine so that you could grind main journals, it will spin just like it would in the engine and will have counterweights and rod journals flinging around as it rotates. If you are grinding a rod journal, the entire thing needs to spin around that particular rod journal and that can be very odd to watch.
Check out this video from Jim’s Automotive Machine Shop to learn more. He give really good info on how this works, the math involved, and the process itself.
Just think, there used to be a lot of “automotive machine” places that could do this kind of stuff. Mad skills, that are harder and harder to find these days.