Set up and operate a variety of machine tools to produce precision parts and instruments. Include precision instrument makers who fabricate, modify, or repair mechanical instruments. May also fabricate and modify parts to make or repair machine tools or maintain industrial machines, applying knowledge of mechanics, shop mathematics, metal properties, layout, and machining procedures. [SOC] Marks & DeLeo list the most important skin allergens as biocides (formaldehyde and Kathon CG), corrosion inhibitors (mercaptobenzothiazole, etc.), nickel, and colophony. Colophony is used as an emulsifier in machining fluids. [Marks, p. 332-5] See the agent "Oil mist, mineral."