Stainless steel stamping parts behave unlike anything else on a press. The alloy work-hardens as you form it, springs back more than carbon steel, and galls against tool steel in a way that ends tool life long before the tool looks worn. Get the grade, clearance and lubrication right and stainless stamps beautifully. Get any one of them wrong and you will spend the program chasing burrs, cracked bends and seized punches. This guide covers the grades worth stamping, how the tooling differs, what tolerances are realistic, and what to put on the drawing.
For the carbon side of the same decision — grades from SPCC to 42CrMo and how each behaves on a press — see our carbon steel stamping guide.
Which stainless grade to stamp
| Grade | Structure | Formability | Typical use | Notes |
|---|---|---|---|---|
| SUS304 / 304L | Austenitic | Excellent | Brackets, covers, clips | Work-hardens fast; 304L for welded parts |
| SUS316 / 316L | Austenitic | Excellent | Marine, medical, food | Better corrosion, higher cost |
| SUS301 | Austenitic | Very good | Springs, clips | Higher work-hardening rate, good spring properties |
| SUS430 | Ferritic | Good | Appliance trim, panels | Cheaper, magnetic, less ductile at tight radii |
| SUS410 / 420 | Martensitic | Fair | Cutlery, wear parts | Harder to form, usually hardened after |
Austenitic 304 and 316 dominate stamped parts because they draw and bend without cracking and stay non-magnetic. Ferritic 430 costs less and is easier on tooling, but its ductility drops sharply at tight bend radii. Martensitic grades are usually formed and then heat treated rather than formed hard.
If the part will be welded after stamping, specify the L grade (304L, 316L). The lower carbon content prevents sensitisation in the heat-affected zone, and it costs almost nothing at quote stage.
Why stainless fights back
Three material behaviours drive every design decision:
Work hardening. Austenitic stainless gains hardness as it is deformed. A bend that is restruck three times can be significantly harder than the as-received coil, which raises tonnage on later stations and accelerates tool wear. Plan the sequence so heavy forming happens early, while the material is still soft.
Springback. Expect roughly 2–5° of springback per 90° bend, against about 0.5–2° for mild steel. Stainless needs pre-forming and restrike stations, or an over-bend compensated by simulation, not a single-hit bend.
Galling. Stainless adheres to tool steel under pressure. The result is material transfer onto the punch, scoring on every subsequent part, and eventual seizure. Lubrication is not optional and tool coating is worth its cost on any program above a few hundred thousand strokes.
Tooling: clearance, material and lubrication
Punch-to-die clearance for stainless runs wider than carbon steel, typically 7–10% per side for SUS304 at 1.5 mm, against 5–8% for SPCC. Wider clearance reduces the burnished-to-fracture contact length and slows the wear mechanism that dominates: adhesion, not abrasion.
| Decision | Carbon steel | Stainless |
|---|---|---|
| Clearance per side | 5–8% of t | 7–10% of t |
| Tool steel | D2 / SKD11 adequate | Carbide or coated above ~300k strokes |
| Coating | Optional | TiCN / AlTiN strongly recommended |
| Lubrication | Flood or mist | Heavy-duty, chlorinated or synthetic extreme-pressure |
| Regrind interval | 100k–200k | 60k–150k, watch burr not appearance |
On tooling economics, the die cost is the same shape as any progressive die — the difference is that stainless pushes you up the tool-steel table faster, which is exactly the trade-off quantified in our progressive die design guide.
Tolerances you can hold
Standard production tooling holds ±0.05 mm on stainless stampings. Precision-ground tooling with restrike and coining stations reaches ±0.025 mm on well-supported features such as hole-to-hole centres within one flat plane. Two limits matter:
- Across a bend, tolerance degrades. A dimension spanning a 90° bend is subject to springback variation and typically opens to ±0.15 mm or worse unless coined.
- Thickness variation in coil stock shifts clearance mid-run. Specify coil to a thickness tolerance and expect burr height to track it.
Anything tighter than ±0.025 mm usually needs a secondary operation. Five-axis CNC machining is the common route when a stamped blank needs a precision bore or sealing face, and it is often cheaper than trying to hold a tight tolerance in the die. Our tolerance guide explains how the budget is allocated across processes.
Burr and edge quality
Stainless burrs are hard and tenacious, which makes them both a safety hazard and a deburring cost. Two rules:
- Specify the burr limit numerically — 8% of material thickness, maximum 0.10 mm, die side — rather than "burr free".
- Watch burr growth as a wear signal. On stainless, burr height climbs before the punch looks dull, because clearance drift and work hardening compound. Track it every 10k–20k strokes.
Finishing after stamping
Stainless stampings usually go out passivated, electropolished, or left as-stamped with a specified surface finish. Passivation restores the chromium oxide layer damaged by tooling contact and is cheap insurance against rust in transit. Electropolishing deburrs and brightens in one step, which often removes a whole secondary operation.
Powder coat and plating are possible but less common on stainless, because corrosion resistance is already the point. Where a colour is needed, mark the part first — the process interaction rules are the same ones described in CNC part traceability marking.
On stampings the code is a forming operation, and our marking on stamped sheet metal guide sets out the location and depth rules that keep it readable after plating.
Cost drivers
For stainless stampings the cost structure is dominated by material, and stainless coil costs several times mild steel, so nesting yield matters more here than on any other material family. A five-point improvement in strip utilisation on a stainless program is worth far more than the same improvement on carbon steel. Tooling amortisation is the second lever, and it is driven by total program volume and regrind interval.
If the annual volume is under about 5,000 pieces, hard tooling rarely pays back and laser-cut-and-bend or low volume CNC machining usually wins. Above 50,000 it is almost always hard tooling. Our CNC machining cost guide breaks the drivers down from the machining side for comparison.
Applications we run
Typical stainless stampings: appliance and equipment brackets, spring clips and contacts from SUS301, medical instrument components from 316L, food-equipment panels, marine hardware, and EMI shielding cans. Where the part also needs machining, we run it as a stamped blank plus a CNC milling or turning operation in the same facility, which avoids the tolerance loss of shipping a blank between suppliers.
Design checklist
- Pick the grade for formability first, corrosion second — both are usually satisfiable with 304L or 316L.
- Bend across the rolling grain, with inside radius at least 1× material thickness (1.5–2× for 430).
- Expect 2–5° springback per 90° bend and design the die for it.
- Specify clearance-compatible tolerances: ±0.05 mm standard, ±0.025 mm precision.
- Put the burr limit on the drawing as a number.
- Specify passivation or electropolish at quote stage.
- Ask for a DFM review before the die is cut.
FAQ
What CNC machining services does Ruijin CNC offer?
Ruijin CNC provides CNC turning, CNC milling (3-axis and 4-axis), 5-axis CNC machining, sheet metal fabrication, metal stamping, and surface treatment including anodizing, plating and powder coating.
What tolerances and certifications does Ruijin CNC hold?
We hold tight tolerances down to ±0.01mm across all processes, and are certified to IATF 16949, ISO 9001 and ISO 13485.
What is the minimum order quantity and lead time?
We accept prototypes from 1 piece with no strict MOQ, provide free DFM review, and return a quote within 24 hours of receiving your CAD drawing and requirements.
How do I get a quote from Ruijin CNC?
Send your STEP file and drawing to gongtianbao@xhlmarketing.com or via WhatsApp +86 17620300785. We reply with a DFM review and a firm quote within 24 hours.
Conclusion
Stainless steel stamping parts reward preparation. Choose an austenitic grade unless cost or magnetism forces otherwise, run wider clearance than you would on carbon steel, specify lubrication and coating as part of the tooling rather than as a consumable, and put burr and tolerance limits on the drawing in numbers.
Ruijin Fenghui runs precision stamping alongside 200+ CNC machines under IATF 16949, ISO 9001 and ISO 13485, with 23+ years of stainless experience behind the tooling choices. Send a STEP file and annual volume and you will have a tooling and piece-price quote within 24 hours — contact us to start, or read how to choose a stamping partner if you are comparing suppliers.