Both put force into the die — holding, stripping, forming — but they behave very differently. Here's how to choose.
What each one does
A coil die spring is a compact helical spring, colour-coded by load class, that drops into a standard pocket. A nitrogen gas spring is a sealed cylinder charged with high-pressure nitrogen pushing against a piston rod. Both resist the press and return the tool — the difference is how much force they give, how that force behaves through the stroke, and how much of it you can control.
Where coil springs win
- Cost. Far cheaper per unit — the default where budget matters.
- Simplicity. Nothing to charge or seal; quick to fit and to replace.
- Good for stripping, ejection and holding in bending and flanging work.
The trade-offs: force builds up with deflection rather than being there from first contact, it fades as the spring fatigues over many cycles, and you often need a lot of springs to reach a target force — which eats space in the tool. A failed coil spring can also break up and damage the die.
Where nitrogen gas springs win
- High force from a small body — far more force per unit volume, so dies can be built with a shorter shut height.
- Near-constant force across the stroke — full force from first contact, not just at the bottom.
- Tunable — set the force by charging pressure, and change it without swapping hardware.
- Linkable and monitorable — connect several cylinders to a manifold and control pressure from one point outside the die.
- Long, consistent fatigue life.
The trade-offs: higher upfront cost, they need charging and occasional maintenance, and each cylinder has a rated load you must stay within.
A simple rule of thumb
Reach for coil springs on simpler, cost-sensitive tools — stripping and holding in bending and flanging. Reach for nitrogen gas springs when you need high, controlled, consistent force in a compact space — drawing dies, progressive and transfer tools, or anywhere force control and die height matter.
IMPEX supplies both from Steinel Normalien — colour-coded system springs and the full nitrogen range (cylinders, composite systems and manifold plates). Send us your pocket size, stroke and target force and we'll match the right part.