Stainless Steel Machining

Stainless steel is our second most-run metal group, and in practice that means two grades: 304 for general corrosion resistance, and 316/316L where the part sees chlorides, chemicals or marine conditions. Both are readily available in Vietnam, which matters more than it sounds — grade availability drives lead time as much as machining does.

We also run 303 and 420 on request, but less often. If your drawing calls for one of them, expect us to ask why before we quote. 303 is chosen for free-machining, but 304 usually machines acceptably and is easier to source; 420 is chosen for hardness, but a hardenable carbon or tool steel is often the better answer. Where 304 or 316/316L meets the technical requirement, we'll say so and quote it — a grade we can buy the same week beats a grade that adds two weeks to your delivery.

Stainless work-hardens, so it rewards correct feeds and sharp tooling rather than brute speed. Budget more machining time than the equivalent aluminium part.

Small, deep holes are where stainless is least forgiving: a dwelling drill hardens the surface it is about to cut. Larger hole diameters and shallower depths, where the design allows, reduce cost and risk.

±0.01 mm as standard, ±0.005 mm on request where the feature allows. Stainless takes a good finish, but the difference between Ra 1.6 and something finer is a separate operation. For sealing faces and round parts that need Ra 0.4 or finer, we finish on our in-house surface grinder (flat faces) or centreless grinder (straight round parts up to Ø40 mm).

Coordinated, inspected on return

Stainless usually needs no coating. Passivation, electropolishing, polishing and sandblasting or bead blasting are available through our finishing partners; part numbers and traceability marks can be laser-marked in-house.

• Tell us at drawing stage which surfaces are critical.
• Specify the finish only on the faces that need it — a sealing land, not the whole part.
• If the drawing calls for 303 or 420, note the reason; we may suggest 304, 316/316L or a hardenable steel.

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