304 Spring Wire - Compensating Springback When Coiling

Product Introduction

TOPONE supplies 304 stainless steel spring wire in 0.15-12 mm diameters for automatic and manual spring coiling. Every coiler knows the wire does not keep the shape it is bent to: it opens up when the coil leaves the tooling. That opening-up is springback, it is predictable, and this page explains how to compensate for it instead of chasing it by trial and error.

Product Specifications

What Sets Springback

When wire is bent around a arbor, the outer fibres yield plastically while the inner layers stay elastic. On release, the elastic layers recover and the coil opens. The amount of opening depends on two numbers that are on your drawing already: the tensile strength of the temper and the ratio of coil diameter to wire diameter. Higher tensile and a larger D/d ratio both mean more springback.

Practical Compensation Rules

• As a starting point, expect the free coil diameter to open by roughly 5-15 percent above the arbor size, growing with tensile class and D/d ratio.
• Harder tempers need smaller arbors, not bigger force - pushing a hard temper around an oversized arbor only raises residual stress and distortion after coiling.
• Keep the D/d ratio above about 4 for drawn tempers; below that, cracking risk rises and a softer temper should be chosen.
• On CNC coilers, pitch and diameter correction on the first article beats trial-and-error on the batch; log the correction per wire lot.

Why Consistent Wire Helps

Springback is only compensable if it repeats. Tensile variation between lots shifts the correction, so a batch-to-batch tensile band that is tight - and stated on the 3.1 MTC - is what makes your first-article setting hold across shipments.

Applications

• Compression and torsion springs on automatic coilers
• Wire forms bent on rotary or 3D forming machines
• Small batches of special springs made on manual tooling
• Zigzag and S-shaped wire elements

Product Advantages

• Tempers with narrow tensile bands for repeatable springback
• Tensile values reported per lot on the 3.1 MTC
• Soap-coated surface for high-speed feeding
• Consistent diameter for stable D/d ratio calculations

Quality Control

Tensile testing follows ASTM A370 / EN ISO 6892 on every coil lot, and diameter is verified along the coil. Cast and helix are checked so the wire feeds straight into the coiler without pre-bending surprises.

Selection and Ordering Notes

1. Give the coil diameter, wire diameter and free length target.
2. State whether the machine is CNC or manual tooling.
3. Choose temper by tensile class, or ask us to match your current springback correction.
4. Confirm surface: bright or soap coated.
5. Request tensile data per lot with the MTC.