Metal Stamping
Also: stamping, pressing, blanking, piercing, sheet metal stamping, stamped parts, punch press, stamping die
Metal stamping blanks, pierces and forms sheet in a hard tool on a mechanical or hydraulic press: high tooling cost, then parts in seconds at pennies each.
1,023 metal stamping companies in the Noramark directory
Stamping puts a strip or blank of sheet between a hardened punch and die in a press. Blanking cuts the outer profile, piercing cuts holes, forming makes bends, flanges, embosses and shallow draws, and coining sets a feature to size. A single-station die does one of these per stroke; a compound die blanks and pierces together; a progressive die does all of them in sequence as the strip advances. Presses run from 20 to 2,000 tons, mechanical presses for speed and hydraulic presses for deep forms.
The economics are a die that costs $5,000-50,000 for simple single-station tooling and $50,000-300,000 or more for a progressive die, followed by parts that come off at 30-1,000 strokes per minute with almost no labor. Material use is high because the strip is nested by the die designer. Below a few thousand pieces a year the die is never paid off and the same part is laser cut and bent; above tens of thousands, nothing else competes.
Cut edges are not sawn faces. A stamped edge has rollover on the punch side, a burnished band about a third of the thickness deep, a rougher fracture zone, and a burr on the die side, so the drawing should say which side the burr may face. Fine blanking, a specialized process, gives a fully sheared edge at the cost of a heavier press. Formed features hold looser tolerances than cut ones, and die wear opens dimensions slowly over the life of the tool.
At a glance
| Typical tolerances | Blanked and pierced features ±0.05-0.13 mm (±0.002-0.005") standard within one station, ±0.025 mm (±0.001") on hole diameters with care, since the punch is a ground tool. Formed features ±0.25 mm (±0.010") standard, ±0.13 mm (±0.005") with care; angles ±1°. Flatness 0.1 mm per 25 mm (0.004"/in). Part-to-part repeatability is excellent once the die is qualified; die wear and material lot changes drift dimensions over long runs. |
|---|---|
| Size limits | Strip widths to about 600 mm (24"), most work under 300 mm (12"). Thickness 0.1-6 mm (0.004-0.250"), with most parts in 0.5-3 mm (0.020-0.125"). Parts from a few millimeters (terminals, clips) to about 600 mm (24") on job-shop presses; automotive body panels run on presses far larger. Bend and draw depth is limited by the press stroke and the die design. |
| Surface finish | The flat faces keep the as-received strip finish (about 1-2 µm Ra, 40-80 µin, for cold-rolled steel). Cut edges show rollover, a burnished band and a fracture zone with a burr of up to 10% of the thickness on the die side; tumbling or vibratory deburring removes it. Forming lubricant is washed off before plating, e-coat or powder coat, which are the usual finishes on stamped steel. |
| Lead time | Simple dies in 3-6 weeks, progressive dies in 8-16 weeks, then tryout samples and first-article inspection. Production runs take hours to days once tooled. Prototypes come from laser cutting and a brake, or from soft tooling, in 1-2 weeks. |
Typical of U.S. job shops; confirm with the shop for your part.
Materials
Low-carbon steel strip (1008/1010, A1008 CS and DS) is the bulk of stamping, followed by HSLA grades like A572 Grade 50 and A1011 for structural brackets, galvanized and pre-painted steel, spring steel (1095, 1074) for clips and springs, and stainless 301, 304, 316 and 410. Aluminum 3003, 5052 and 6061-O stamp well; 6061-T6 only with generous radii. Brass C260, copper C110 and beryllium copper C172 are the electrical and connector materials. Anything sold as coil or sheet in the right temper can be stamped; cast alloys, tool steels and plate over about 6 mm (0.25") cannot.
What drives the cost
- Die cost: number of stations, hardened D2 or carbide sections, in-die tapping or forming
- Annual volume: the die is amortized across it, and the run length sets the setup share
- Material: strip price, thickness, and the scrap fraction the strip layout leaves
- Press tonnage and bed size, which the part size and the material set
- Secondary operations: tapping, deburring, plating, assembly, packaging
- Tolerances that need coining, fine blanking or shaving
- Part complexity: forms, draws and features that need cams or extra stations
When to use it
- Tens of thousands to millions a year of a sheet-metal part
- Brackets, clips, springs, terminals, washers, shields and shallow formed parts
- Parts whose profile and holes need ±0.05 mm (±0.002") repeatability
- Replacing a laser-cut and bent part whose volume has grown past the die cost
When not to
- Under a few thousand pieces a year: laser cutting and press-brake forming cost nothing in tooling
- Designs still changing: every revision is a die modification
- Deep cups and shells: deep drawing on a transfer press
- Thick plate, machined features or variable thickness: machining, forging or casting
- Parts that need a smooth sheared edge with no fracture zone unless fine blanking is on the table
Design tips
- Make holes at least one material thickness in diameter (1.2t in stainless) and keep them 1.5-2t from edges and bends.
- Put radii of at least 0.5t on the outside corners of the blank; sharp corners chip punches and start cracks.
- Use an inside bend radius of 1t and keep bends the same radius; state the grain direction where a tight bend matters.
- Say on the drawing which side the burr may be on and how high it may be, or ask for deburring.
- Tolerance cut features tightly and formed features loosely; the die can hold what the punch cuts, not what the sheet springs to.
- Ask the stamper for a strip layout before the die is built and check the scrap rate and the carrier location.
- Prove the design with laser-cut and brake-formed prototypes before tool steel is cut.
- Give the annual volume and the expected life of the part so the shop can size the die class (soft, semi-hard, carbide).
Frequently asked questions
- How much does a stamping die cost?
- A single-station blank or pierce die runs $3,000-15,000; a compound or simple forming die $10,000-50,000; a progressive die $50,000-300,000 and more for large or carbide-section tools. Add tryout, first-article inspection and, in automotive work, PPAP. The die is usually owned by the buyer and kept at the stamper.
- What quantity justifies metal stamping?
- Compare the die cost against the per-part savings over laser cutting and bending. A part that costs $4 laser cut and bent and $0.40 stamped pays off a $15,000 die at about 4,000 pieces; most stampers want 10,000 or more a year. Below that, stay with laser and brake.
- What is the difference between stamping and laser cutting?
- Laser cutting profiles each part from a program with no tooling, so it wins at low volume and for changing designs; a stamping die cuts and forms the whole part in one stroke, so it wins on cost and consistency at volume. Many parts start on a laser and move to a die when the volume proves out.
- What is fine blanking?
- A stamping variant that clamps the strip with a V-ring and blanks it under a counter-pressure so the edge is fully sheared with no fracture zone, holding ±0.025 mm (±0.001") and near-square edges on gears, ratchets and latches. It needs a triple-action press and a specialist shop.
- How long does a stamping die last?
- A tool-steel die is good for 100,000 to a few million strokes between sharpenings, and carbide sections extend that to tens of millions. Die maintenance (regrinding the punches and die sections) is normal and should be in the quote; abrasive materials, thick stock and tight tolerances shorten the interval.
