Pro tip: Stop fighting with rusty hooks, use a wire brush wheel on a grinder
For years I was spending 20 minutes per hook with a hand file trying to clean up old lifting hooks on job sites in Houston. Now I just throw a knotted wire wheel on my 4.5 inch angle grinder and hit them for 2 minutes tops. The difference is night and day, especially on those old manitowoc hooks. Has anyone else switched to power tools for hook maintenance?
Bring up the safety issue, but I'm coming at it from a different angle. @sandra_sullivan84 is right about hiding cracks, but I've found wire wheels can also whip those little metal bristles loose at like 10,000 RPM and they stick right in your forearm. I always wear a thick welding jacket over my regular work shirt now when I'm cleaning hooks with a grinder, saved me a lot of trips to the urgent care for splinter removal.