Stainless Steel Sheet Metal Fabrication

Stainless steel is the material buyers ask for when the part has to survive washing, salt, chemicals or public handling — and it is also the material where a low price usually means somebody has not thought about the weld. This page sets out what we cut, bend, weld and finish in 304, 316 and 430, what the drawing has to say for the job to come out right, and where the work leaves our building.

Which grade, and why it decides the whole route

Grade selection is not a price decision alone; it decides how the part must be welded, finished and inspected. These are the three we run most often.

If you already have a grade on the drawing we build to it. If you do not, tell us the service environment — indoors, washdown, coastal, chemical — and we will say which of the three we would choose and why, rather than defaulting to 304 because it is the common answer.

What changes because the material is stainless

Laser cutting

Stainless is cut with nitrogen rather than oxygen, which gives a clean edge with almost no oxide to grind off. Our three laser cutters — two 3,000 W and one 6,000 W — cut stainless sheet from 0.5 mm up to 15 mm. Above roughly 12 mm the cut speed falls and the edge starts to taper, so thick plate is a job we will quote honestly on cut time rather than promise at a thin-sheet rate.

Bending

Stainless springback is larger than mild steel, so the bend allowance on the drawing and the tooling setup both matter more. Our four CNC press brakes are rated 250 tonnes with a 3,000 mm bed, which lets us form a cabinet side or door in one setup instead of splitting it and welding it back together — one less weld, one less grinding step, one less leak path. Tight inside radii on thin stainless are achievable but the material is prone to cracking if the radius is pushed below what the temper allows, and we will say so at quotation stage instead of finding out on the bending machine.

Welding and heat tint

Welds are where stainless most often fails: heat tint and unremoved free iron are the start of corrosion, and distortion shows up as soon as the part reaches the customer. We run ten welding stations in the same building as cutting and bending — TIG for visible seams, jigged and sequenced to hold flatness rather than just to join the parts. After welding, tint and scale are removed mechanically and the part goes for passivation.

Finishing stainless

This is the part of the page where we are specific about what we do ourselves, because buyers who visit will check.

• Brushing and mirror polishing run in our own workshop. Grain direction, grit sequence and the surface finish are agreed against a sample panel before production. On parts that read as a set — a run of panels, a door and its frame — we agree the grain direction and the joint line so the finished assembly looks deliberate rather than assembled from pieces.
• Passivation, electropolishing and any plated finish go to audited applicators. We specify the method or the class on the drawing, and check the result on receipt. We do not operate a plating or anodizing line, and we will not tell you we do.
• Powder coating, where a colour is wanted instead of bare metal, is applied on partner lines that we specify and inspect.

Because brushing is in-house, a brushed panel and its welded frame can be finished as one matched pair. That is the practical reason buyers move this work to a single fabricator rather than buying bare parts and arranging finishing themselves.

What to put on the drawing

• Grade, and the temper if it matters (annealed, 1/4 hard, 1/2 hard)
• Welded or riveted construction, and whether the weld is visible or dressed flush
• Finish: brushed (with grain direction and grit), passivated, electropolished, or powder coated to an RAL reference
• Surfaces that must stay conductive, or be masked from coating
• Any food-contact, washdown or chemical-exposure requirement, so grade selection is not left to the shop floor
• Inspection document requirements — mill certificates, first-article report, or a specific format from your incoming inspection

How we inspect and what travels with the shipment

Every batch is checked against the drawing revision we quoted. Measuring equipment is height gauges and coating thickness gauges — we do not have a coordinate measuring machine, and we say so rather than claiming positions we cannot verify. If your drawing needs a capability we do not have, you will hear it at quotation stage.

Material certificates matched to the sheet we cut, a first-article report against the quoted revision, and in-process and outgoing inspection records travel with the batch. Our quality system is documented to ISO 9001. We do not hold a third-party ISO 9001 certificate and we do not claim one; what we can offer for review under NDA are the third-party audit references TUV Rheinland MIC-ASI243729 and Bureau Veritas MIC-ASR263630.

Lead time and what we need to quote

• Simple samples: 3–7 days. Complex first article: 15–20 days. Production batch: 25–35 days.
• Tooling is quoted separately, and is not included in sample time: 7–15 days simple, 30–45 days complex.
• Quotations are issued after drawing review, not from a price list.

Send 2D drawings (PDF, DWG or DXF) and 3D models (STEP, IGES or SolidWorks) with quantity, grade, finish and destination. We will come back with a quotation, the DFM points we would change, and a straight answer on which steps are ours and which are the applicator’s.

Choosing between brushed, passivated and electropolished stainless depends on where the enclosure lives, not on which finish looks best in a photograph. We go through that decision by failure mode on the stainless and aluminum enclosure finishes page — including the sequence that has to be right for a welded assembly to passivate properly.

Related reading: surface treatment for stainless steel · stainless steel bending guide · metal surface finishing · custom sheet metal fabrication