photograph of an extension spring
Extension Springs

Product Order Line:
01527 521000

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Spring Directory

Select wire diameter below


Specifications & Materials

Music Wire to DIN 17223, Class C. No.1.1200 or BS 1408 CR3.

Stainless Steel Wire to DIN 17224, No.1.14310 or BS 2056 302S26.

Ends: German loops, random position

Note: All Springmasters Extension Springs are right hand coiled.

Tolerances: All dimensions and forces conform to DIN 2095 (Grade 2) or BS 1726 Class B.

Surface Finish:
Music Wire = Oiled
Stainless Steel = Self

Recommended Working Temps:
Music Wire = 120°C (max.)
Stainless Steel = 300°C (max.)

Product Order Line: 01527 521000

Minimum order charge for UK & Rep. of Ireland customers: Orders are subject to a minimum charge of £15 plus carriage, packing & VAT. Minimum order per item £2.50.

Minimum order charge for Overseas customers: Orders are subject to a minimum order charge of £50 Pound Sterling ($100 US Dollars) on an ex-works basis.

Choose from the selection of wire diameters on the right ----»

Search extension springs database

Or... input your specifications to our recently added extension springs database to locate the spring that matches your requirement.

Resistive force springs

Extension springs, also known as tension springs, apply a resistive force as the spring extends and are commonly utilised to move or return a component part. Extension springs require special ends to permit application of the load and these ends assume many forms.

Manufacture and stockist

We manufacture and stock extension springs, see the right-hand column and choose from the different wire diameter sizes available. We also have an extension spring database enabling you to locate the spring that matches your requirement and contact Springmasters, with the spring code number, for a competitive quote!

Custom Spring design

We can also manufacture to your specific requirements if we do not stock an extension spring in the size you require. We have the capability to produce millions of extension springs and the flexibility to manufacture a 'one-off'.

Taking quality control seriously

Our team of engineers and quality control personnel monitor each stage of the production of compression springs, using both computer and manual SPC systems, to ensure that this aim is achieved.

Assorted Boxes of Extension (Tension) Springs

Buy online... assorted imperial and assorted metric extension springs.

Information for students and graduates.

We are starting to locate and collate a list of educational resources which we feel would be very useful to budding engineers and springmakers alike.

Please contact us if you are aware of an excellent educational web page or site about extension (tension) springs and feel it should be included in the list below.

Coil Spring Terminology
Wikipedia: Coil Springs
Springs: Description, Problems and Solutions
Extension Springs

Extension Spring Formula.

Design of extension springs is virtually the same as that of compression springs, the formulae for rate and stress being identical.

Extension springs, however are different in two ways. Firstly, they are normally close-coiled whereas in compression springs the coils are open. Secondly, initial tension can be put into extension springs so that a particular load has to be applied to the spring before the coils begin to open.

This can only be done in springs manufactured from cold-drawn material and the maximum initial tension which can be obtained is calculated as follows:

W1 = Initial tension load
S1 = Initial tension stress
d = Wire diameter
R = Mean radius of coil

The initial stress is taken from the following table.

(D over d)
(D over d)
(D over d)
(D over d)
(D over d)