Here’s a resourceful DIY engine builder who found some scuffing or discoloration on the factory Mitsubishi crankshaft in what appears to be a 4G63 4-banger. Instead of taking the crank down to the machine shop for a polish, he rigged it up in the block using the two forward main caps for support. After a trip to the local home improvement for tape and scrounging micron paper from his shop, he hooked up a big drill and polished the crankshaft by hand. The journals clamped under the main caps were freed up when the crank swapped ends.
The results don’t appear harmful, and the poster says he mic’d the journals. A little bit of searching on the web revealed it’s not all that uncommon to polish a crank in a home shop. EngineLabs found photos on a Toyota forum with a crankshaft stand made from plywood and a bow for the sanding belt made from a yardstick. Again, a drill was used to turn the crank.
Never overlook the ingenuity of engine builders!