We also use emery paper to smooth out rough surface finishes on machined parts. None of my tools but some of the tools the other guys have in the shop use little Ruby beads as reference surfaces. Our wire EDM also uses Ruby for some critical parts.
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Is it possible that they aren’t calling you because you’re over qualified?
It’s not uncommon to be standard practice to filter out anyone who’s over qualified because they tend to get bored, and they’ll ask for a lot more than less qualified candidates will.
They’re betting that some will leave, most will stay, and even if the some that leave are the best, most of their money is made by the vast majority of people behind them.
They’re looking at trends, not individuals. Individuals don’t matter to them.