Metaphors for Hardness

        Starting after the middle of the 20th century, I began working with machinists and skilled construction tradesmen of all kinds.  I was impressed by the abundance of colorful metaphors they used in almost every line they spoke.   For instance, some of the expressions used to describe various kinds and degrees of hardness included:
 "Harder than a whore's heart",
  "Harder than the hubs of hell",
  "Harder than Chinese arithmetic",
  "Harder than a Nicholson file", and
  "So hard a cat couldn't scratch it."
  Only the reference to Nicholson files had any concrete reference point in the real world,  but they all served to convey the notion of really, really hard.  As a young man, I was fascinated by this style of narrative, and wish today that I had bothered to write some of it down.  Is there a modern day equivalent to this type of jargon? Do people still do this?