304 Stainless Steel: CNC Machining and SLM Printing

304 stainless steel is the corrosion-resistant workhorse of equipment design — the grade behind most enclosures, brackets and fittings that live in wet, washed or corrosive surroundings. At Arterki you can order 304 stainless steel two ways: CNC-machined on our three- and five-axis milling centers, or printed on our metal SLM line, where 304 is the launch alloy. Both routes ship with an inspection report.

Quick answer: We CNC-machine SUS304 in-house to a routine tolerance of ±0.05 mm (±0.02 mm negotiable, confirmed against metrology), lead time confirmed at quotation, and we print 304 stainless on our metal SLM line with in-house heat treatment. An engineer reviews every drawing, quotes come back within 24 hours, and every shipment carries an inspection report.

304 at Arterki: CNC-milled and turn-milled in-house — routine tolerance ±0.05 mm, ±0.02 mm negotiable with metrology confirmation, lead time confirmed at quotation. Metal SLM at launch alloy 304 stainless, with in-house heat treatment; 316L, 17-4PH and titanium sit on the metal-line roadmap — ask for a quote. Inspection report with every shipment.

304 stainless capability at Arterki

These are the parameters a quote commits to. Anything your drawing needs beyond these rows goes in the RFQ, and the quote returns with each item confirmed against the shop schedule and our metrology equipment before a number is promised.

The two lines that decide most orders. Tolerance: ±0.05 mm is our routine class on machined 304; where a drawing calls ±0.02 mm on specific features, we verify against our metrology equipment before quoting, so the promised number and the inspected number are the same number. Process: machined 304 gives you the full bulk properties of wrought stock and fine finished faces; SLM-printed 304 buys geometry — internal channels, consolidated assemblies, lattices — that machining reaches only with great cost. The rest of this page helps you choose.

For the services behind the machines, see our CNC machining and metal SLM pages.

When 304 stainless is the right call

Parts in wet or corrosive surroundings. Enclosures, sensor housings, brackets and fittings exposed to washdown, condensation or mild chemicals are 304's home territory — the corrosion resistance is in the alloy, applied by your drawing rather than by a coating.

Structural parts with a hygiene-adjacent washdown requirement. Equipment frames and guards that get hosed down regularly stay bare-metal and inspectable in 304.

Fittings and small turned parts. Our turn-milling cell covers small precision turned features — bosses, threaded fittings, bushings — in one setup where the drawing allows.

Complex metal geometry. When a part wants internal cooling channels, conformal passages or a shape that would need five setups and a wire EDM, SLM-printed 304 consolidates it into one printed body. See our metal SLM service for the workflow.

Reach for aluminum 6061 when corrosion resistance is manageable and weight or machining speed matters more; reach for 316L when chlorides dominate the environment — see the comparison below for current routes.

Design notes for 304 stainless

304 machines well but has habits worth designing around:

Work hardening. 304 hardens under the cutting tool, so deep, narrow pockets and light repeated passes cost time and tool life. Give cutters room: open pockets, standard tool radii, and tolerances placed on features that functionally need them.

Clamping and thin walls. Stainless cuts take real force. Thin walls and long overhangs need support strategies that show up in price — mark non-critical features as such and we will confirm the achievable tolerance at quotation.

Tolerance placement. Call out the critical dimensions on the drawing. The inspection report measures what you mark critical; unmarked features are inspected visually.

For SLM parts: orientation and support strategy. Printed 304 needs support structures on overhangs, and orientation drives residual stress and surface quality. We review orientation with you before the build, and every print goes through in-house stress relief before it reaches inspection.

For SLM parts: design for the process. Internal channels, consolidated assemblies and self-supporting angles overhang less and print more predictably. Send the CAD early — a short DFM pass at quotation beats a redesign after a build.

304 compared with alternatives

Strength and corrosion figures vary by grade, condition and test direction. Describe the environment (chlorides, temperature, load) in your RFQ and the quote comes back with a material recommendation.

Metal SLM 304: what ships, what's next

304 stainless is the launch alloy on our metal SLM line. Printed parts come off the platform, receive in-house stress-relief heat treatment, and go to inspection with the same report discipline as our machined parts. For programs that need 316L, 17-4PH or titanium: those alloys sit on the metal-line roadmap, and current status is confirmed with your quote — tell us the alloy and the application, and we will answer plainly about timing.

Questions engineers ask

What tolerance can you hold on machined 304?

Machining holds ±0.05 mm as our routine class, with ±0.02 mm negotiable on the features that justify it. We verify the achievable limits against our metrology equipment before quoting, and your inspection report records a measured value for every dimension you mark critical.

What tolerance do SLM-printed 304 parts hold?

SLM tolerance depends on geometry, orientation and feature size, so we confirm it per geometry at quotation instead of quoting a page-level number. Mark the critical dimensions on the drawing and the quote states what we will inspect to.

Can you print 316L, 17-4PH or titanium?

316L, 17-4PH and titanium sit on our metal-line roadmap, with 304 stainless as the current launch alloy. Send the alloy, the application and your timeline in the RFQ and we confirm current status with your quote — plainly, before the order starts.

Machined or printed 304 — which should I order?

Machine it when bulk wrought properties, tight tolerance or fine surface finish decide the test, and the geometry fits tool access. Print it when internal channels, consolidated assemblies or complex geometry would otherwise mean EDM, five-axis setups and braze joints. Send the part and we will quote both routes with the same DFM pass, so the decision is a line item rather than a guess.

Do 304 parts need passivation?

State the passivation or surface requirement in your RFQ. Bead blasting and heat treatment run in-house; plating and coating work is arranged via certified partners and folded into your schedule at quotation. Requirement-specific documentation is assessed at quotation and confirmed in writing before the order starts.

304 or 316L for my environment?

For fresh water, mild chemicals and standard washdown, 304 is the economical default. Persistent chlorides — salt spray, brines, some cleaning agents — tip the choice toward 316L. Describe the actual environment in your RFQ and the engineer who quotes the part will recommend one with the reasoning stated.

What's in your inspection report: every critical dimension measured against the tolerance class in your quote, the process route as ordered — machined or SLM, heat-treated — and visual condition. Proof that follows the part from our floor to your build.