you really don't need lube very often, in my experience.
Sterling Silver, no lube
some brass alloy is the worst stuff in the world to cut, and others cut like sterling silver. Sometimes lube, most often, no.
mild steel, cuts like buttah, no lube required, but may be used.
Alloy steel, tempered steel, lube is required, cobalt cutting tools last much longer than HHS.
gold cuts best with highly polished CARBIDE gravers, gold sticks to steel gravers.