A heavy duty extension spring made to drawing in spring steel, for applications where the pull is measured in hundreds of newtons rather than tens. These are designed around the working load and the safety margin, not selected from a size list.
Wire diameter, coil count and free length are calculated against the force and travel you specify rather than approximated from a catalogue.
Heavy springs concentrate substantial stress at the hook. Hook form and transition radius are designed as part of the spring, not added to it.
For heavily cycled heavy duty springs, shot peening puts the surface into compression and extends fatigue life.
Never fit a heavy duty extension spring without a retention arrangement that captures it if a hook fails. A heavily loaded spring releases a substantial amount of stored energy.
Standard springs stacked in parallel to reach a load one properly designed spring should carry
Hook failures on heavily loaded springs bought on dimensions rather than designed on force
Dimensional and load figures are set per order against your drawing or sample, so they are marked TBC rather than filled with catalogue numbers.
| Product Type | Tension Springs |
|---|---|
| Raw Material Options | Stainless steel, Spring steel, Carbon steel, 65Mn, Music wire |
| Wire Diameter Range | 0.1-8 mm |
| Surface Treatment Options | Zinc plating, Nickel plating, Silver plating, Gold plating, Tin plating, Galvanizing in various colours, Dacromet, Black oxide, Phosphating |
| Standard | ISO, non-standard and OEM drawings |
| Processing Route | Material sourcing → Coiling and forming → Heat treatment → Surface treatment → Quality inspection → Packing → Shipping |
| Inspection Equipment | Grinding and shot peening machinery; Precision tensile strength testers; Magnetic powder flaw detectors |
| Packing | Plastic bags, cartons or pallets, or packing to your own specification |
| Payment Terms | L/C, T/T, D/A, D/P, Western Union, 30% deposit before production, 70% balance before shipment |
| Lead Time | 7-15 days after the order is confirmed |
| Minimum Order Quantity | Quoted per part — tell us your requirement (TBC) |
| Dimensions and Load Rating | Made to your drawing or sample (TBC per part) |
Every batch follows the same seven step route, with tensile testing and magnetic powder flaw detection carried out before packing.
Available in Stainless steel, Spring steel, Carbon steel, 65Mn, Music wire, in wire from 0.1-8 mm, with any of our nine surface finishing routes. Geometry, end treatment and finish are all specified per order.
ISO 9001, SGS certificate and RoHS report (stated on the legacy site, certificates pending re-confirmation). Certificate copies are sent on request once re-confirmed.
Against parallel standard springs, one designed heavy duty spring gives a predictable force and one failure point instead of several, and needs a single well designed anchor rather than a row of them.
Tell us the margin your standard requires. We design to your stated working load and factor rather than assuming one.
Tell us what the anchor requires and we will confirm at quoting what end treatment is achievable in your wire size.
Usually yes, for predictability. Parallel springs share load unevenly unless they are matched, and a single designed spring avoids the issue.
Send your drawing, dimensions or a sample. We will confirm the specification and come back with a price and a lead time.