About 50 years ago, I met a retired mechanic (that is what they were called back then), and he impressed upon me that when working on any piece of machinery, that it must be relatively clean, and when you were done, you clean all your tools before putting them away. He told me that you could take any tool out of his tool box, and run it across a white shirt, and it wouldn't even leave so much as a smudge. I am not that meticulous, but I do keep all my tools clean, and for the most part, you can wipe them with a white cloth and it will not leave a smudge. I use my tools, but I don't abuse my tools, and I always try to put them away clean. I have one place on the bench that I keep them if they are dirty, until they are cleaned and put back in the box. Only short coming of this is that occasionally, I misplace a tool, and don't realize it until cleaning day. Almost always, they do show up after doing a search.