Direct answer: metal stamping cuts and forms sheet metal on a press. The process follows the part, not the other way round — flat multi-feature parts go on a progressive die, larger or deeper forms on a transfer die, smooth-cut edges to fine blanking, and a closed seamless body to deep drawing. The tool is usually the largest single cost and the longest item in the schedule, and tolerance grades (ST1–ST11 for flat parts, FT1–FT10 for formed parts under GB/T13914-2002) decide a large share of it. This page is the working version of what we tell buyers before they send a drawing.
What stamping does, and where it stops
Stamping covers blanking, piercing, bending, forming, coining, extruding, tapping and trimming. What those operations share is that the material starts as sheet or coil and never becomes a different shape of stock. A stamping press runs a tool that cuts and forms in one or more stations, and the piece price falls as the volume rises because the tool cost is spread over more parts.
It stops in three places. A closed, seamless body deeper than roughly half its own diameter is not stamping — that is deep drawing, and it needs a draw die, a blank holder and often several draws with annealing between them. A part whose geometry is turned or bored from bar is machining. And a part with a smooth, fully sheared edge thicker than a few millimetres is fine blanking, which uses a different press and a V-ring rather than a conventional die.
Which process fits your part
Five families cover almost everything we quote. The decision comes down to how many features the part carries, how much the material has to flow, and how many parts a year the tool has to earn back.
| Process | What happens in the press | Where it wins | Where it does not |
|---|---|---|---|
| Compound die | Blank and pierce in a single stroke | Flat parts, high volume, tight flatness | No forming, no bends, no draw |
| Progressive die | Coil feeds through stations; each stroke adds features | Multi-feature flat and formed parts, medium to high volume | Long strip layout; corrections late in the design are expensive |
| Transfer die | Separate stations, parts carried between them | Larger parts and deeper forms than a strip can carry | Slower than a progressive die; needs more floor space |
| Fine blanking | High-pressure blanking with a V-ring and counter-punch | Smooth cut edges, tight flatness, thick material | Blank-shaped parts only; tool cost is higher |
| Deep drawing | Blank is drawn into a die to form a seamless cup or housing | Sensor housings, solenoid valve bodies, motor cans | Not for sharp corners or square profiles |
Where a part needs both a drawn body and stamped features, the two run in the same tool or on the same line — which is what the term deep draw stamping actually describes. We quote both routes where they are close, so you can see the crossover volume.
The tool is the project
Tooling is where a stamping project is won or lost, because the tool sets both the piece price and the date the first good part exists. Six things move the tool cost:
- Number of stations. Every additional station adds a die block, a set of punches and another chance for the strip to mis-feed.
- How far the material has to flow. A draw that needs three steps instead of one costs roughly three times the forming stations and usually an annealing step between them.
- Material. Austenitic stainless work-hardens and needs larger radii and more conservative steps than mild steel; 65Mn spring steel needs its own springback allowance.
- Tolerance. A feature held to a machined-feature tolerance has to be built, shimmed and maintained that way for the life of the tool.
- Cam work. Side holes, undercuts and reverse flanges need cam slides, which are the most maintenance-hungry part of any die.
- In-die operations. Tapping, coining or a staking operation inside the tool removes a secondary operation but adds tooling and tryout.
We design and build our tools in-house, in the same plant as the presses. That matters for a practical reason: when the strip layout or a station has to change after tryout, the people who designed it walk to the press and change it. A tool built by a third party goes back on a truck. Read more about in-house tooling design and build.
Materials we run every week
The list below is what actually goes through our presses, not a catalogue of everything that exists:
| Family | Grades | Notes |
|---|---|---|
| Carbon steel | DC01, DC04 (EN 10130); cold-rolled and hot-rolled 1008–1020 | DC04 is the usual choice for drawn housings; hot-rolled is cheaper but leaves a rougher surface |
| Stainless steel | 301, 304, 304 DDQ, 305, 309, 310, 316 / 316L, 430 | 304 is the reference grade; 430 is magnetic and needs flatter draw steps |
| Spring steel | 65Mn | Spring cups and clips; springback has to be built into the tool |
| Copper alloys | Brass C2600 / CDA 655, copper | Thermal and electrical parts; CDA 655 carries marine applications |
| Aluminium | 1100-O, 3003-O, 6061-O | Roughly a third of steel's elastic modulus; needs different lubricants and larger radii |
| Nickel alloys | Inconel 625, 718 | Only where temperature or corrosion demands it; both work-harden fast |
Our published sensor housing configurations run wall thicknesses from 0.25 mm to 1.00 mm, with 0.50 mm the most common. Whatever grade you specify, the useful step is the same: tell us the function the part has to perform and let us confirm the grade, because a cheaper grade that needs one more draw step is not cheaper.
Design rules that decide the piece price
These are the points we check first on a new drawing. None of them is exotic; all of them move the price.
- Hole-to-edge distance. Keep it at least one material thickness, preferably two, or the edge bulges and the punch breaks out.
- Bend radius. Half a thickness is workable in mild steel; austenitic stainless wants a full thickness because it work-hardens at the outside of the bend.
- Distance from a bend line. Holes and slots closer than about 1.5 thicknesses to a bend line need a relief notch, or the feature distorts.
- Tolerance placement. Tolerance the function, not the drawing. A cosmetic face and a sealing face do not need the same figure.
- Grade count. Every additional material grade and thickness in one order adds setup and stock, and the price reflects it.
- Asymmetry. A part that is not symmetric about the strip centreline can rotate in the tool; adding a carrier feature usually costs less than the scrap it prevents.
Tolerances a stamping can hold
For flat stampings, GB/T13914-2002 defines eleven grades, ST1 to ST11, from tightest to loosest. Formed stampings use ten grades, FT1 to FT10. In practice, a formed feature on a small part holds around ±0.1 mm routinely; anything tighter has to be machined after forming, and the drawing should say so, because a tolerance that has to be met by a machining operation should not be asked of the press. The full grade tables, and where you can relax a figure without losing function, are on the stamping tolerance charts.
Documentation you can file
Balford works to ISO 9001:2015 processes. For series programmes the quality team releases first-article inspection reports and PPAP-compliant documentation, and provides IMDS data for automotive part numbers. Dimensional and geometric checks run in our own inspection lab; where a formal CMM report is required, the measurement is organised through a partner lab and flagged before the quotation. Material traceability comes from mill certificates held against the batch.
What runs in-house, and what does not
In-house: tool design and build, stamping, deep drawing, CNC machining, tube bending and coiling, and assembly. Outsourced: surface treatment (plating, coating, passivation) and heat treatment. We name the outsourced steps on the quotation rather than leaving them to be discovered later, because a buyer planning an audit needs to know which operations happen under someone else's roof.
How a project runs with us
- Drawing. A 2D PDF with tolerances, plus a 3D model if you have one, and the material, annual volume and finish.
- DFM review. Draw ratio, blank size, station count, material thinning and cost drivers are checked against the drawing. Most reviews come back within 24 hours.
- Quotation. Tooling and piece price, separated, with volume breaks so you can see where the tool pays back.
- Tool build and tryout. First-article inspection before the tool goes into production, with the report sent to you.
- Production. Scheduled runs with in-process checks, and PPAP-compliant documentation where the programme needs it.
Frequently asked questions
What is the difference between stamping and deep drawing?
Stamping cuts and forms sheet in a tool; deep drawing pulls a flat blank into a die to form a seamless cup or housing. In production the two are usually combined in one tool, which is why the phrase deep draw stamping exists. The distinction that matters commercially is that a draw needs a blank holder and often several steps, so it costs more tooling than a flat stamping of the same size.
How much does a stamping tool cost?
It depends on the six drivers above, and the honest answer is that the same part can be tooled for very different sums depending on station count, draw steps and tolerance. That is why we quote tooling and piece price separately: you can then see what a looser tolerance or a simplified feature saves, instead of arguing about a single number.
What volume justifies a progressive die?
When the annual volume amortises the tool within the programme you have in front of you. Below that, a compound die, a transfer die or soft tooling for the prototype stage usually costs less overall. If you send the annual and lifetime volume with the drawing, the quotation will show the crossover.
Can I get parts before the tool is built?
Yes, for proving fit and function. Prototypes can be laser cut, CNC machined or formed on soft tooling, and we will say which route suits the geometry. Prototype parts are not a substitute for first-article parts from the production tool, and the quotation says so.
Which tolerances should I put on my drawing?
Tolerance the faces that do something: sealing faces, bearing seats, mating features. For everything else use the loosest grade that still functions — ST or FT grades from GB/T13914-2002 give you a scale to choose from, and the tolerance charts page lists them. A drawing where everything is tight is the most expensive drawing we see.
Where to go next
- Metal stamping services — what we run, and the equipment behind it
- Deep drawing — the process, the tooling and the limits
- Progressive die stamping — strip layout, stations and tool life
- Precision stamping and fine blanking — smooth-cut edges
- Tolerance charts — ST and FT grades in full
- Draw force calculator — check the tonnage your part needs