Stainless steel stamping

304 and 316L both work-harden, but 316L is tougher and more abrasive on tooling. Die clearance is typically tighter than for mild steel, and lubricant choice matters because chlorinated lubricants can leave a residue that attacks the passivated surface. Deep drawing stainless usually needs inter-stage annealing.

The commercial consequence is that stainless is priced on its own material line, not blended into a steel rate. Material grade, thickness, tolerance and finish are quoted separately from conversion, so a change of specification is visible in the price.

Ganesh quotes to the drawing first and to ISO 2768 general tolerances where the drawing is silent. For stainless stamping, the practical starting points are in the table below. They are starting points, not a guarantee: the part geometry, thickness and fixturing decide what can actually be held, and the quotation states the tolerance offered.

Blanking, piercing, forming and drawing are quoted as one press route; the number of stations, not the tonnage alone, usually decides whether a part is worth tooling. Stainless must be cut with high-pressure nitrogen to keep the edge oxide-free; that is the difference between a weldable edge and one that has to be pickled. The route is quoted as one sequence so the customer does not have to coordinate a cutter, a former, a welder and a coater.

Stamping stainless is the wrong route when the volume does not justify the tool and the part is a simple bracket; laser cut and form holds the finish better and avoids die pick-up on a short run.

A manufacturability review before quotation is the cheapest place to find this out. Send the drawing, material, finish and annual quantity and the review comes back in writing.

• Food and pharmaceutical brackets
• Trim and cover plates
• Clips and retainers
• Housings and covers

Use stamping when the geometry is frozen and the annual quantity repays the tool. As a working rule, a simple bracket in a single-stage tool becomes cheaper than laser-cut-and-formed at roughly 3,000–8,000 parts a year; a progressive tool needs more volume because the tool itself costs more. Below that range, laser and bend keeps the cash free and the revision cheap. Between the two, quote both and compare total cost over the programme life, not the first order. For stainless the practical constraint is contamination: carbon steel tooling, brushes and blast media transfer free iron, so stainless work is kept on dedicated tooling and its own handling. Stainless raises the stakes on the decision: tool wear, gas cost and slower forming mean the volume needed to justify a tool is higher than for CRCA, and the wrong early choice is expensive to reverse once a die has been cut.

State the material grade and blank thickness, the tolerance on every functional feature, the burr direction and height where it matters, the grain direction if the part is drawn, and whether the tool is customer-owned or supplier-built. Name the inspection level. If the part will be welded, say so, because the burr and the flatness that a welding fixture needs are not the same as for a plain bracket.

Inspection covers dimensional features, burr height, material thickness and hardness at sample frequency, plus a first article report before production. Ganesh holds tools in the in-house tool room, so die maintenance records and tool history are available with the part. PPAP documentation is available where the programme requires it.

Cost splits into material, tooling, press time, secondary operations and inspection. Tooling is a one-off and is quoted separately, so the piece price only makes sense against an annual quantity. Press time is driven by stroke rate and the number of stations, not by part weight. Secondary operations such as deburring, tapping, welding and coating often exceed the press cost on a small part. On stainless steel, material is quoted as its own line at the prevailing rate for the grade and thickness, so a change of specification is visible rather than hidden in a blended rate.