The plain double hook extension spring that most enquiries start from: a coiled body with a machine loop at each end, supplied in whatever wire size, length and finish the application needs. It is the baseline part against which the rest of this category is specified.
Wire from 0.1 to 8 mm, any practical free length, and any of nine surface finishes from one part family.
The machine loop is the lowest cost and most robust hook style, appropriate wherever the anchor is a plain pin.
Equally straightforward to reproduce from a sample as to make from a dimensioned drawing.
Measure free length inside the hooks, not overall, when specifying a replacement. Overall length varies with hook style and causes most of the confusion in extension spring ordering.
Sourcing several extension spring sizes from separate distributors at distributor prices
Replacement springs that are dimensionally close but give the wrong 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 side loop and extended hook variants, the machine loop version is the cheapest and most robust. Choose a different end only when the anchor geometry demands it.
Wire diameter, outside diameter, free length inside the hooks and the load you need at working length. A sample covers all of it.
Zinc plating for dry indoor use, galvanising outdoors, stainless where it is permanently wet. Tell us the environment and we will recommend.
Yes, and it usually works out better than quoting them separately, since they can run in the same production window.
Send your drawing, dimensions or a sample. We will confirm the specification and come back with a price and a lead time.
