I’ve been using electrolytic rust removal for quite a while now, but this method never ceases to amaze me!
Here’s how I found the chuck, it came with a milling machine I acquired a few months ago, the previous owner had left some tooling in a rotten shed and this is the end result.
It was frozen shut. In theory the electrolysis should not affect the inside portion of the chuck, because it isn’t in the line of sight with the anode — but I had my hopes this could just work by freeing up the rust near the jaws and the collar.
Surprisingly after a few hours the chuck was in working order!
I did remove the arbor later on, not sure how they were using it like that, the inside of that arbor is hollow and threaded, but it has no surface to register with, aside from the flat face on the hexagonal portion — odd, maybe it was meant to be screwed onto a turret tool blank for a capstan lathe?
So there you have it, you CAN turn your archaeological finds into usable tooling, assuming no apes were previously involved.