Resource
How to measure a spring
Five numbers get most quotes moving: wire, outer diameter, free length, coils, and the end or hook type. Metric first.
What you need
A ruler marked in millimetres, and a way to read wire diameter — a digital caliper is enough for a first pass. We do not publish a list of instruments used on this floor.
Every spring
- Wire diameter d. Measure across the wire, not along it. Rate changes with the fourth power of d, so this number matters most.
- Outer diameter OD. Across the coil, outside to outside. If the spring works in a hole or over a rod, write that diameter as well.
- Free length. Unloaded. For an extension spring, length inside the hooks. For a torsion spring, the free angle between the legs.
- Coils. Count every coil you can see. Say whether that is total coils or active coils if you know the difference.
- Ends. Open, closed, closed and ground; hook type; leg shape and wind direction.
By type
Compression. Add solid height if you can close it by hand without force, and one working length with the load you need there. See the compression spring page.
Extension. Length inside hooks, hook type and whether the openings face the same way. Initial tension if you know it. See end types.
Torsion / double torsion. Both leg lengths and shapes, free angle, working angle, shaft diameter, wind direction, and the centre-loop width on a double torsion spring.
What to send
A photo next to a ruler, the numbers above, the quantity, and the material if you know it. Or post an unused spring. We measure it and quote within 24 hours. Usual minimum 5,000–10,000 pcs.
Wire outside Ø 0.40–2.50 mm is outside our range.