Metal Stamping Presses: Types, Tonnage and What to Ask a Shop
The press decides how fast a part runs, how deep it can form and what the die has to withstand. Here are the main press types, their typical ranges and the specs that matter when you compare shops.
Press types
Tonnage ranges are typical for each type and vary by builder. A press is chosen for the die it runs, so the die and the press are specified together.
| Press | Typical tonnage | Where it fits | Limit |
|---|---|---|---|
| Gap frame mechanical | Up to about 300 tons | Single stage dies, blanking and small brackets. Open front gives easy die access. | The C shaped frame flexes under load, so it is a poor base for long progressive dies. |
| Straight side mechanical | About 60 to 1,000 tons and up | Progressive and transfer dies for brackets, shields and housings. The workhorse of production stamping. | Fixed stroke and slide motion, set by the crank. |
| High speed mechanical | About 20 to 250 tons | Terminals, connectors, lead frames and small laminations on thin strip at 400 to 1,500 strokes per minute or more. | Small bed, shallow forming. Needs a precision feed and a die built for the speed. |
| Servo | About 40 to 1,000 tons and up | Forming, drawing and coining where slide speed and dwell at the bottom of the stroke change the result. | Higher price and, at equal tonnage, often a lower stroke rate than a mechanical press on simple blanking. |
| Hydraulic | About 50 to 1,000 tons and up | Deep draws, large panels and forming that needs full force through a long stroke. | Slower cycle. Force and stroke are set by pressure and limit switches, not a crank. |
| Knuckle joint | About 100 tons and up | Coining, embossing and sizing. Delivers its full force in a short stroke at the bottom. | Short stroke, so it does not suit tall parts or deep draws. |
| Transfer press | About 100 to 1,000 tons and up | Larger and deeper parts. Has a built in transfer system and several die stations in one bed. | Large floor space and a die set that is built only for that press. |
| Fine blanking press | About 100 to 1,000 tons | Thick flat parts with a fully sheared edge. Applies three forces: shear, clamp and counter pressure. | Costly press and tools. Limited to blanking, piercing and light forming. |
A fourslide or multislide machine forms wire and strip with cam driven slides and has no press rating. Read about fourslide parts.
Five numbers to ask a shop for
These tell you whether a press can run your die. Ask for them for the press the quote assumes, not for the largest press in the plant.
- Rated tonnageA mechanical press delivers its rating only near the bottom of the stroke. Ask for the force available at the height where your die works.
- Bed sizeThe die has to fit with room for clamps and the strip. Long progressive dies need a long bolster.
- Shut height and strokeShut height has to match the die. Stroke length sets how tall a part the press can form or draw and how fast it runs.
- Strokes per minuteStroke rate sets parts per hour and so the piece price. A part that runs at 80 spm costs less than one at 20.
- Coil capacityMaximum coil width, weight and inner and outer diameter. A small coil means more changeovers and more scrap at each end.
Pairing a press with a part
Starting points. The shop picks the press that fits its die and its schedule.
- Thin strip, small parts, high volumeHigh speed mechanical press with a servo roll feed and a die with sensors.
- Brackets and housings in steelStraight side mechanical press, 100 to 300 tons, with a progressive die.
- Deep cups and shellsHydraulic or servo press with a die cushion, so the blank holder force can be set.
- Coined or embossed detailKnuckle joint or servo press, so full force arrives at the bottom of the stroke.
- Stainless, HSLA or thick stockMore tonnage and more energy per stroke. The same part needs a larger press than in mild steel.
- Large panelsTransfer press or a tandem line, where each press handles one operation.
Equipment around the press
Two shops with the same press can deliver different results. The equipment around it decides scrap, uptime and how fast a die gets fixed.
Coil line
Uncoiler, straightener and leveler. They remove coil set and camber before the strip enters the die.
Feed and lubrication
A servo roll feed sets pitch accuracy. Oiling keeps friction and galling under control, most of all on stainless and aluminum.
Die protection
Sensors for misfeed, short feed and part out. They stop the press before a fault wrecks the die.
Tool room
Wire EDM, sinker EDM, surface and profile grinders and CNC mills. A shop with its own tool room can fix a die the same day.
Part handling
Robots, conveyors and containers that keep parts from scratching and tangling.
Inspection
Optical comparator, CMM, vision and height gauges. The equipment has to match the tolerance on your print.
Machines that replace a die at low volume
Below a few thousand pieces a year, a hard die rarely pays off. A laser or turret punch cuts the blank and a CNC press brake forms it, with little or no tooling. Piece price is higher and lead time is short.
- Laser or turret punchCuts blanks and holes from sheet with no die.
- CNC press brakeForms bends from the blank with standard tooling and a programmable back gauge.
- Bridge toolingA low cost die that runs the first lots while the production die is built.
Frequently asked questions
What tonnage press does my part need?
The press has to cover the cutting force, which grows with cut length, thickness and material strength, plus forming loads and a margin. Shops calculate it from your print. Stainless needs roughly one and a half times the tonnage of mild steel for the same cut.
Is a servo press better than a mechanical press?
Not always. A servo press controls slide motion, which helps forming, drawing and coining. For simple high speed blanking, a mechanical press often runs faster and costs less per hour.
Does a long press list mean a shop can make my part?
No. A press list shows capacity, not experience. Ask for a part close to yours in material, thickness and die type, and for the press it ran on.
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