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Most rejected finishing lots trace back to a drawing that did not say clearly enough what had to stay clean. Here is how to mark one up so it gets quoted and run right the first time.
Masking is the least glamorous part of finishing and the most common cause of a rejected lot. Almost every masking problem we see traces back to the same root: the drawing did not say clearly enough what had to stay clean.
The electrical group causes the most expensive surprises. Coating is an insulator. A part that looks perfect can fail a bonding-resistance check because nobody marked the ground point on the drawing.
A note reading “mask critical surfaces” is not actionable. Cross-hatch the areas on the drawing view, or dimension them. If it is on the print, it gets protected; if it is in an email, it gets missed.
Masking has an edge, and that edge has tolerance. Tell us how much overspray or pull-back you can accept at the boundary — especially near a sealing face.
These are different requirements. A surface that must stay bare metal is masked. A surface that can take a coating but not the thickness may just need a thin-film process instead — a much cheaper answer than intricate masking.
If a maximum matters, it is a real requirement and should be measurable. A stated range lets us pick a process that can actually hold it rather than discovering the problem at inspection.
Threads that must gauge after coating need masking or chasing. Say which, and say who does it. Assumption in either direction costs a lot.
Heat-sensitive inserts, bearings, seals and electronics change the process entirely. Even a note as short as “nylon bushing pressed in” saves a phone call and possibly a scrapped lot.
Survives the cure oven without adhesive transfer, cut and applied to the marked boundary.
Threaded holes, bores and studs get plugged or capped to keep coating out of features that have to gauge or press.
On repeating production work, a purpose-made mask or fixture is faster, more repeatable and cheaper per part than hand masking every run.
A cost note worth hearing. Masking is labour, and labour is per part. On a high-volume job, an hour spent at the drawing stage deciding what genuinely needs protection — rather than masking everything defensively — often takes more out of the piece price than any other single change. Ask us at quote time; we will tell you which callouts are driving the number.
Threads and bores that must gauge or press, sealing faces and O-ring grooves, locating features, and every electrical bonding or grounding surface. Coating is an insulator, so continuity surfaces are the ones most often missed.
Graphically — cross-hatch or dimension the areas on the drawing view. A general note saying “mask critical surfaces” is not actionable and will generate a question at quote time.
Yes. High-temperature masking tape and silicone plugs are standard parts of our process. Call the features out on the print and we will protect them.
Yes, and it is labour, so it scales with quantity. On production work it is worth reviewing which callouts are genuinely required — defensive masking of everything is usually the largest avoidable line in a finishing quote.
That is a different requirement from “no coating,” and it often has a cheaper answer — a thin-film process such as Cerakote instead of intricate masking. Say which one you mean on the drawing.
Very much. It usually rules out an oven cure and pushes the job to a liquid or thin-film process. Note anything heat-sensitive on the print or in the RFQ.
We will tell you which callouts are driving the price and which ones you can drop.
