Extension springs


Varianti Ltd. manufactures custom extension springs according to the needs and exact requirements of its customers. For its production processes, Varianti Ltd. uses round cross section wires. The wires’ diameters in Varianti’s range of production of extension springs are 0,2 mm ÷ 10,0 mm.

Extension springs are springs with densely wound bodies and hooks, loops or eyes on both ends, which serve to attach the springs to other components. The body coils are often coiled with an initial tension and it is the initial tension that determines how tightly the coils are wound. By their nature, extension or tension springs, are springs working on forces that pull both ends apart and change the spring in shape. When both ends are extended, the spring is actually trying to resist the tensile force bringing back the ends and restoring the close coiled shape of the body. In general, these springs are designed to oppose extension. Just like compression springs, extension ones absorb and store energy when forces are being applied longitudinally on their axis, but they act in the opposite manner to compression ones.

There is a great variety of hook or loop and body shape configurations in order to fit a precise function of the extension spring. They can be made cylindrical, conical and barrel-shaped with a multitude of hook types:

conned loop½ German eyelet / Half loop over center (bild 2)






standard loopStandard full German loop / Single full loop over center (bild 3)





double twisted loopDouble twisted loop / Double full loop over center (bild 4)






side raised hookSide full loop / Full German loop at side (bild 5)






double full loopDouble full loop at side (bild 6)





raised hookRaised hook / long round end hook over center (bild 7)






side raised hookSide raised hook / long round end hook at side (bild 8)






full loopEnglish full loop over center / English eyelet (bild 9)





conned loopConed swivel loop / crazy hook (bild 10)




 But many other loop variations are possible.


Extension springs have multiple applications. They are used in automotive interiors and exteriors, medical devices, farm machinery, carburetors, garage doors, washing devices, trampolines, pliers, lawnmowers, garden tools, toys, as well as thousands of other usages.

For an adequate quotation we need to consider several key parameters:

  • Outer Diameter (Da /De) and/or Medium Diameter (Dm);
  • Wire Diameter (d /dr);
  • Wire Tolerance – admissible deviations (± X mm) from the wire and spring diameters, as well as from the spring length (Lo);
  • Number of work coils (N/n/if);
  • Pitch – the distance center-center between two adjacent coils (t) (in case the relevant extension spring has such, if not – the pitch equals the wire diameter, which means that the spring body has tightly wound coils);
  • Free Length (Lo);
  • Body Length (Lk);
  • Loops’ type;
  • Loops’ orientation one to another (0°, 90°, 180°, 270°);
  • Loops’ height (Lh) or Lh1 and Lh2 in case both loops have different heights;
  • Loop Clearance/Gap – dimension that defines the loop opening (m);
  • Forces in N/mm the extension spring is planned to resist to incl. Initial Tension (N);
  • Wire quality (stainless or carbon steel + standard);
  • Finishing spring treatment (galvanization, oxydization, powder coating, phosphating, ZINTEK 200).

Submit us with those key parameters mentioned above, a drawing or a sample and we will provide you with a pricing for a single spring or millions of them.

Production capabilities for extension springs:



Production range 1: Production range 2: Production range 3:
Wire size: Ø0,2 ÷ 10,0 mm Ø0,2 ÷ 6,5 mm Ø2,0 ÷ 10,0 mm
Material: Carbon Steel Spring Wire Stainless Steel Spring Wire Oil Tempered Spring Wire
Standard: EN 10270-1-DH-SH-SM-DM EN 10270-3, 1.4310, AISI 302/304 EN 10270-3-VD/FD SiCr
Shapes: Cylindrical, Coned End, Barrel Type (Convex)

Large variety of hook types according to German standard DIN 2097 and upon request:  


half German eyelet bild 2, standard full German loop bild 3/single full loop over center, double full loop over center bild 4,

side full loop bild 5, double full loop at side bild 6, raised / extended eye over center, long round end hook at side bild 8, English full loop over center bild 9, crazy hook / swivel hook coned end bild 10, coned end with swivel bolt bild 11, small eye over center, small eye at side, 1/2 winding / reduced loop bild 15

machine cut plain ends, small offset hook at side, offset hook tension spring, v-hook over center, square hook, drawbar extension spring etc.

Direction of winding: Left Hand or Right Hand
Finishing: Zinc Coating, Oxydization, Powder Coating, Phosphating, ZINTEK 200
Quantity: From 1 piece and small series order to a large volume of millions.