Why carbon steel still wins most stamping programmes
Carbon steel stamping is the default choice for stamped components that need strength, wear resistance and a predictable price — brackets, clips, frames, reinforcements, motor laminations, spring contacts. Aluminium wins when weight or corrosion resistance leads; stainless wins when corrosion does; brass and phosphor bronze win when conductivity or spring behaviour does. But when the brief says "strong, cheap, millions of them", the answer is almost always a plain low-carbon or medium-carbon strip.
That does not make it simple. The grade you pick changes the tooling, the lubrication, the achievable tolerance and the surface treatment you need afterwards, and those four decisions are locked in at die design. This guide covers the grades actually used in production, how each behaves under a progressive die, what tolerances and burr limits to expect, and the four cost drivers that move a quote.
The grades that matter
Stamping grades are chosen for formability first and strength second, because a part that cracks in the draw station never reaches the strength question.
Which steel the cutting edge is made of, and how long it holds that price, is the subject of our stamping die material guide.
| Common designation | Roughly equivalent | Carbon content | Typical use |
|---|---|---|---|
| SPCC / DC01 / SAE 1008–1010 | Low-carbon cold-rolled | ~0.08–0.10% | Covers, brackets, deep-drawn shells, general stampings |
| SAE 1010–1020 | Low to medium carbon | 0.10–0.20% | Structural brackets, clips, weldments |
| S45C / SAE 1045 | Medium carbon | ~0.45% | Shafts, wear plates, parts later heat-treated |
| 40Cr / SAE 5140 | Low-alloy chromium | ~0.40% | Higher-strength structural parts |
| 42CrMo / SAE 4140 | Low-alloy chromium-molybdenum | ~0.40% | High-load parts, usually quenched and tempered |
| 20CrMnTi | Low-alloy case-hardening | ~0.20% | Gears and wear parts for automotive |
A practical split: low-carbon grades (SPCC, 1008–1020) form well and weld well but are soft, so they gall and they need protection against rust. Medium-carbon and low-alloy grades (S45C, 40Cr, 42CrMo) hold strength and take heat treatment but are harder on tooling and less forgiving in tight bends. We stock and run both families, and our machining materials guide carries the full list with machining notes.
One thing buyers rarely specify and should: temper and surface condition of the strip. Cold-rolled full-hard, half-hard and annealed strip of the same grade behave completely differently in a die. A part drawn successfully from annealed SPCC may crack from full-hard SPCC of identical chemistry.
How carbon steel behaves in a progressive die
A progressive die carries the strip through a sequence of stations — pierce, notch, form, draw, trim, cut-off — one hit at a time. Four properties of carbon steel drive how that sequence is designed.
Springback. Carbon steel springs back more than aluminium and less than high-strength stainless, but the amount varies with yield strength, which varies with temper and with the coil. A 90° bend specified without a bend allowance will land somewhere between 88° and 92° in production. Compensation is built into the die, which means a die built for one temper cannot be assumed to hold for another.
Burr formation. Every sheared edge on a stamped part has a burr. On carbon steel the burr grows as the punch-to-die clearance drifts and as the punch edge wears, and low-carbon grades produce a ductile burr that rolls over rather than breaking clean. Standard commercial practice permits a burr of roughly 10% of material thickness, and a burr limit should be written on the drawing rather than assumed.
Galling and pick-up. Soft low-carbon strip has a tendency to transfer material onto the punch under high contact pressure, especially at high speed. This is a lubrication and tool-steel problem, and it is one reason high-speed stamping programmes specify tool coatings and a lubricant regime up front.
Work hardening. Each forming station work-hardens the material. For most parts this is harmless or helpful. For parts with a deep draw followed by further forming, it is the reason an intermediate anneal appears in the process.
Where the geometry allows the part to be rotated and transferred rather than carried on a carrier strip, a transfer die may suit better; where the part is flat and pierced in one hit, a compound die is faster and more accurate. Our stamping overview sets out how we choose between the three.
Thickness, tolerances and what to expect
Standard stamping thickness for carbon steel in our shop runs 0.2 mm to 3.0 mm, with the majority of commercial work between 0.5 mm and 2.0 mm. Below 0.2 mm the strip becomes hard to feed consistently; above 3.0 mm the tonnage and tool wear start to argue for laser cutting or machining instead.
| Feature | Typical achievable tolerance | Notes |
|---|---|---|
| Hole diameter, pierced | ±0.05 mm to ±0.10 mm | Depends on thickness and punch size |
| Hole-to-hole within one station | ±0.05 mm | Best case: pierced in the same hit |
| Hole-to-hole across stations | ±0.10 mm to ±0.20 mm | Accumulates with strip pitch error |
| Blank overall length | ±0.10 mm to ±0.30 mm | Grows with part size and number of stations |
| Bend angle | ±1° to ±2° | After springback compensation |
| Bend leg length, to a bend | ±0.15 mm to ±0.30 mm | Bend location is less accurate than a pierced hole |
| Flatness | 0.10 mm to 0.30 mm over 100 mm | Depends on residual stress and strip condition |
| Burr height | 5% to 10% of thickness | Specify a limit on the drawing |
The single most useful thing a buyer can do is separate the features that matter from the features that do not. A bracket with 60 dimensions generally has four that decide whether it assembles. Tolerancing those four to ±0.05 mm and leaving the rest to a general note keeps the die simpler, the tool life longer and the price lower. Our tolerance guide goes deeper on how general tolerances should be written on a drawing.
Note also what stamping cannot do. If a design needs a true-position callout of ±0.02 mm on a hole pattern, or a machined flat, the honest answer is a second operation on a CNC mill or a machined part from the start.
Surface treatment: carbon steel rusts
This is the decision that most often gets left too late. Bare carbon steel will flash-rust in transit, sometimes within days in a humid container. Every stamped carbon steel part needs a specified finish, and the finish affects the tooling sequence because parts must be clean and dry before coating.
| Finish | What it gives | Typical use |
|---|---|---|
| Zinc plating, clear or yellow | Sacrificial corrosion protection, 5–15 µm | General hardware, brackets |
| Nickel plating | Harder, brighter, better wear | Contacts, decorative hardware |
| Powder coating | Thick decorative and protective layer | Visible covers, enclosures |
| Black oxide | Thin, mild protection, no dimensional change | Internal parts, tools |
| Phosphate plus oil | Cheap, good paint base, temporary protection | Parts painted later by the customer |
Zinc plating remains the default for most stamped steel hardware. Where a part must remain electrically conductive or must be welded afterwards, plating has to be specified around those requirements. More detail on each process is on our parts finishing guide.
The four things that actually move the price
Buyers often assume stamping price is driven by material. In practice, for a part that runs in the hundreds of thousands, it is driven by four other things.
- Tooling complexity. Every extra station is more die sections, more setup time and more maintenance. A part that can be made in six stations is meaningfully cheaper than the same part in eleven, and the difference is usually a design detail — a hole moved one millimetre so it can be pierced in the same hit as its neighbour.
- Material utilisation. Strip layout decides scrap. On a high-volume part, moving from 62% to 71% material utilisation is a larger saving than any negotiation on steel price.
- Tolerance and burr specification. Tighter callouts mean more frequent punch sharpening and more inspection. Specify what assembly needs and nothing more.
- Annual volume and release pattern. Tooling is amortised. A die that costs a fixed amount is cheap per part at 500,000 a year and expensive at 5,000. Tell your supplier the real annual volume; a die designed for the real number is a different die.
Prototypes are a separate question. Before a die exists, small quantities are usually cut by laser or wire and formed on a brake, or machined; our prototyping notes and low-volume guide cover that stage.
Low carbon steel stamping: where the grades split
Low carbon steel stamping covers the SPCC / DC01 / SAE 1008–1010 band and, at its upper edge, SAE 1010–1020. The split that matters to a buyer is formability against strength: 1008–1010 draws and bends readily and welds without preheat, which is why it owns covers, brackets and deep-drawn shells, while 1010–1020 carries more strength for structural brackets and weldments but is less forgiving in tight bends and needs a larger inside radius.
Two specifications decide whether a low carbon steel stamping programme runs cleanly. The first is temper — cold-rolled full-hard, half-hard and annealed strip of the same grade behave completely differently in a die, and a die compensated for one temper cannot be assumed to hold for another. The second is the burr limit: low carbon grades form a ductile burr that rolls over rather than breaking clean, so the allowable burr height belongs on the drawing instead of being left to a supplier default.
Specifying the part: a short checklist
- Grade and temper, not just grade — "SPCC, annealed" is a complete specification; "SPCC" is not.
- Thickness with a tolerance band, and the coating or surface condition of the strip.
- Burr height limit and which side it is permitted on.
- The four or five critical dimensions called out individually; everything else under a general tolerance note.
- Finish, with thickness, colour reference and any conductivity or welding constraint.
- Annual volume and the expected release pattern.
Send those six items with the drawing and a stamping quote comes back in hours rather than days. If you would rather start from "here is the assembly, what should this part be", our DFM service is built for exactly that. Ready to price a part? Send the drawing and volume — we quote within 24 hours.
FAQ
What is carbon steel progressive stamping?
Carbon steel progressive stamping feeds a coil of low- or medium-carbon steel strip through a single die in which the part is carried on a carrier web past a line of stations — pierce, notch, form, draw, trim, cut-off — one press stroke at a time, advancing one pitch per stroke. Because one die performs every operation, the piece price falls sharply once the tooling is paid off, but changing the part later means changing the die. The process suits flat to moderately formed components run in volume: brackets, clips, frames, reinforcements, spring contacts and motor laminations. Our progressive die guide sets out how those stations are laid out.
Which grade should I pick for progressive stamping carbon steel?
Choose formability first and strength second, because a part that cracks in the draw station never reaches the strength question. SPCC, DC01 and SAE 1008–1010 cover covers, brackets and deep-drawn shells; SAE 1010–1020 cover structural brackets and weldments; S45C, 40Cr and 42CrMo come in when the part is later heat-treated or carries real load. For progressive stamping carbon steel, specify temper and strip surface condition alongside the grade — annealed and full-hard SPCC share identical chemistry and behave completely differently in the same die, so a form that draws successfully from one may crack from the other.
How do progressive stamping and fabrication differ?
Progressive stamping and fabrication solve the same problem with opposite economics. Stamping cuts the part from coil with a dedicated die: high tooling cost, low piece price, very fast cycle and tight repeatability from part to part. Fabrication cuts flat sheet by laser or turret and forms it on a press brake: very low tooling cost, higher piece price, slower per part, and far more tolerant of design change late in the programme. Tooling is amortised, so below roughly five thousand parts a year fabrication usually wins on total cost, while at hundreds of thousands a year stamping wins on both price and consistency. Machining is the third route and worth comparing wherever tolerances drop below what either forming method holds; see stamping versus CNC machining.
Do stamped carbon steel parts need a burr limit on the drawing?
Yes, and it belongs on the drawing rather than in an assumption. Every sheared edge carries a burr, and on carbon steel the burr grows as the punch-to-die clearance drifts and the punch edge wears, with low-carbon grades producing a ductile burr that rolls over rather than breaking clean. Normal commercial practice permits roughly 5% to 10% of material thickness. State the permitted height, which side it is allowed on, and which edges must be deburred afterwards; our deburring guide covers the options. Specifying a tighter limit than assembly actually needs buys more frequent punch sharpening and a higher quote.
What is carbon steel metal stamping best suited to?
Covers, brackets, clips, weldments and deep-drawn shells, where formability and weldability matter more than ultimate strength. Low carbon grades (SPCC, 1008-1020) dominate that work; medium carbon grades appear when the part is heat-treated or carries structural load.