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

Surface rust or discoloration can be caused by contamination from the workpiece, water, coolant, or handling. Deposits often collect in screw holes, counterbores, and other areas with limited fluid flow.

Clean the affected areas with a soft cloth and a suitable mild stainless steel cleaner, then dry the fixture. Check the filtration and water condition. Easily removed deposits may be surface contamination; persistent corrosion, damaged reference surfaces, or changes in clamping performance require further inspection.