What’s the English word for the metallic “dust”, or more precisely the tiny remains (waste) of drilling, welding, cutting through metal, and similar metal processing?
You could generally use Swarf, which also works for other materials too.
Swarf generally implies relatively big pieces of waste though, "metal dust" would be acceptable if you really do end up with a very fine powder.
Additionally, when grinding something, people tend to refer to the metal that goes flying as sparks
In the jewellery trade it is known as lemel or lemels. An alteration of earlier limall, limmell, from Middle English lemaille, limail, from Middle French limaille, from Old French, from limer to file, from Latin limare. (Merriam-Webster Online)
Though in all the years of living with my father, a Silversmith, I never heard him use the word. He simply called it filings or scrap, depending on size. Though it was always assiduously collected.
The metalwork equivalent of sawdust is "swarf"
The OED has this as:
Fine chips or filings of stone, metal, or other material produced by a machining operation:
For the small pieces that come off from a machining process like drilling, milling, or turning on a lathe, these are often called turnings if you are selling them to a scrap hauler. The smallest "dust-sized" pieces that would come from grinding or saw-cutting are sometimes also known as filings or fines.
When I learned to program a CNC laser some years ago, I was taught to call the small waste metal pieces that indicated a less than perfect cut dross. This same waste from an plasma cutter or oxygen-acetylene torch would more usually be referred to as slag, although I always saw little difference between the two terms.
For residue produced from machining: I'd vote for "filings" if the residue is small and dust-like. For bigger bits of leftovers, as in those left over from lathe work, the term I've heard is "chips". (Trivia du jour: I used to work at a specialty steel maker who produced steels specifically designed to ensure good chip breakage - i.e. that didn't leave those long and potentially problematic "curls" of (sharp!) steel).
For welding or cutting residue: I've heard it referred to as "spatter".