What 3-A Actually Asks of a Machined Component

September 27, 2026

3-A Sanitary Standards certify finished dairy and food processing equipment, not the individual machined parts that go into it. That distinction matters, because it means the standard’s requirements reach your drawing indirectly, through what the equipment builder specifies, rather than through a certificate you can put on the component itself.

What 3-A actually is

The 3-A Sanitary Standards organisation publishes voluntary standards, developed jointly by equipment makers, processors and regulators, covering the design and construction of dairy and food processing equipment. Equipment can be evaluated and authorised to display the 3-A symbol once it meets the relevant standard.

A machined valve body, fitting or shaft is a component of that equipment, not the equipment itself, so it is not separately 3-A certified. What matters for your part is that the equipment builder buying it needs the component to meet the same material, finish and geometry clauses the whole assembly is built to, or the finished equipment cannot pass evaluation.

The three clauses that land on a machined part

Material. 3-A standards specify acceptable materials for product contact surfaces, and stainless steel of the austenitic type, corresponding to 300-series grades, is the default expectation. This is the standards-level reason 316L is specified so often on food and dairy parts, alongside the practical chloride resistance covered in stainless for food contact.

Finish. Product contact surfaces are specified at 32 microinch Ra or better, about 0.8 micrometre, unless a specific 3-A standard within the family sets a different number for that equipment type. This is a maximum average roughness, not a guarantee against a single deep tool mark or torn inclusion. See what Ra actually measures.

Geometry. Cleanable design: no sharp internal corners on product contact surfaces, radiused instead so a brush and a cleaning solution actually reach them, no threads or crevices in product contact zones and no horizontal ledges that hold liquid after a system drains. These are drawing decisions, not machining defects, and a shop will build exactly what the print specifies.

What this means for a component drawing

Write the clauses that actually apply to your part, not the word sanitary or 3-A compliant, which a shop cannot quote against:

Material: 316L stainless, ASTM A276 Product contact surfaces: 32 microinch Ra maximum (approximately 0.8 micrometre) Internal corners in product contact areas: R3 mm minimum No blind threads or crevices in product contact zones Passivated per ASTM A967, citric, certificate required

That specification is the same one used in stainless for food contact, because the underlying requirement is the same whether or not the finished equipment is pursuing 3-A authorisation. Most machined component drawings should carry it regardless, since the same finish and geometry serve any food safety audit, 3-A or otherwise.

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Where this differs from NSF and FDA

NSF/ANSI 51 is a separate standard covering food equipment materials more broadly, and it is the one referenced more often outside dairy specifically. The material and finish expectations for a machined part are similar in practice.

FDA 21 CFR 177 covers food contact substances, which mostly means the plastics, coatings and elastomers used around a stainless part rather than the stainless itself, since stainless steel is not the section of that regulation doing the work.

For a machined component, the practical takeaway across all three frameworks is the same: correct grade, documented, at the specified finish, passivated, with the geometry a cleaning process can actually reach. Certification of the assembled equipment is the equipment builder’s responsibility, and neither we nor any single machine shop certifies a component on its own. We place your RFQ with partner shops that already work to these material, finish and geometry requirements, and you name the documents you need back on the RFQ.

See also: NSF/ANSI 51 for stainless food equipment parts, on what the materials standard covers and how to check an NSF listing.

Frequently asked questions

Figures in this guide are published specification limits or published typical values for the alloy, not measurements of any part. Machinability is rated against free-machining carbon steel B1112 at 100 and PREN is chromium plus 3.3 times molybdenum plus 16 times nitrogen. The conventions are set out in thereference section and the editorial standards.

Keep reading

• Salt spray testing of stainless parts: what a pass proves, what it misses and which test to name instead
• Cleanroom packaging for machined stainless parts: bags, caps, labels and what the cleanroom class really covers