Preventing CNC Machining Scratches During Handling

CNC machining scratches often occur after the spindle stops, during deburring, inspection, and packing. Soft alloys such as 6061-T6, 7075, and 304 stainless, plus plastics like POM/Delrin, show handling marks easily, and a single wipe across a chip can exceed a Ra 0.8 finish requirement. Treat finished surfaces as a controlled feature, not scrap to sort later.

Keep parts separated through every transfer. Use divided trays or foam inserts, never stack machined faces, and blow chips away before wiping. Gloves help with fingerprints but can trap grit; inspect and change them. When moving parts between operations, use soft jaws or dedicated carriers, and avoid re-clamping on a finished datum. A small nick on a sealing face can cause a leak path even when dimensions pass.

Deburr with tools matched to the edge and material. A hand scraper on 6061-T6 can roll metal onto a cosmetic face; a controlled chamfer or brush is safer. Mark cosmetic and functional zones on the drawing, and state whether ISO 2768-m is acceptable outside those zones. For visible surfaces, define Ra and any allowed marks so inspection does not become a debate.

Packing is the last chance to prevent CNC machining scratches. Use individual bags, peel film, or VCI paper for stainless; avoid direct contact with cardboard, which can hold abrasive dust. Ask the shop to document handling controls for high-value lots. These steps add little cost compared with rework, but they protect lead time and the finish you paid for.

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For more guidance on related work, see: CNC Pocket Design: Corner Radii That Cut Cost.