Why does a rust-proof chuck develop surface rust or discoloration?

Surface rust or discoloration on rust-proof chucks can come from contamination introduced by a workpiece, water, coolant, or handling. The chucks are made from 440C stainless steel; external deposits do not usually affect their performance.

Deposits collect most readily on unground surfaces, counterbores, screw holes, and areas with limited water flow. Check water quality and filtration to reduce further contamination.

Clean the affected areas with a soft cloth and a mild stainless steel cleaner. Scrub areas where deposits collect at the end of each day and dry the fixturing.