Q1. What is an extension spring?

A. An extension spring is a spring that produces a restoring force when it is pulled apart. It usually has hooks, loops, or special end configurations at both ends for connection to other components. In simple terms, it is designed to return toward its original length after being extended.

Q2. What is the main function of an extension spring?

A. Its main functions are to provide pulling force, restoring force, maintain tension, or help a component return to its original position. When a mechanism is pulled open, the spring can pull the part back or maintain tension in a specified direction.

Q3. Where are extension springs commonly used?

A. Extension springs are used in structures that require pull-back, return, or maintained tension.

    - Automotive and motorcycle components
    - Tools, clamps, and linkage mechanisms
    - Door latches, locks, and furniture hardware
    - Sports and fitness equipment
    - Power tools, garden tools, and toys
    - Machinery, automation equipment, and commercial equipment

Q4. Can the hooks at both ends of an extension spring be customized?

A. Yes. Hook design is an important part of an extension spring. End configurations may include half-round hooks, loop hooks, long hooks, short hooks, offset hooks, double hooks, swivel hooks, or hooks with special angles. The hook shape affects installation, load direction, and service life.

Q5. What information should a customer provide when requesting a quotation for an extension spring?

A. Please provide a drawing with complete dimensions, including wire diameter, outside diameter, opening dimensions, free length, and hook dimensions.

    - Also specify the number of coils, winding direction (left-hand or right-hand), hook shape, hook orientation, material, surface finish,
      extension travel, force requirements, and operating environment.
    - The more complete the information, the more accurate the quotation will be. A 3D drawing is also helpful if available.

Q6. What is initial tension?

A. Initial tension is the force created by the coils being held tightly together before the extension spring is pulled apart. It affects the force required to begin extending the spring. If the application is sensitive to pulling force, the initial tension should be clearly specified.

Q7. How far can an extension spring be stretched?

A. The allowable extension depends on wire diameter, outside diameter, number of coils, material, heat treatment, and service-life requirements. If the spring is extended beyond its designed travel, it may deform, fail to return, or suffer hook breakage. Customers should provide both the normal working length and the maximum extended length.

Q8. Where is an extension spring most likely to break?

A. Common risk areas include hook bends, end connections, and locations subject to long-term stress concentration. Hook radius, load direction, installation angle, and possible side loading should therefore be considered during design.

Q9. Can an extension spring remain stretched for a long period of time?

A. Yes, but it must be designed for a long-term extended condition. If it is held beyond the safe working length for an extended period, the spring may lose force or become permanently deformed. The customer should provide the actual operating conditions and acceptable service-life requirements.

Q10. What are body length, overall length, free length, hook orientation, extension travel, and force requirement for an extension spring?

A. Body length: the length of the coiled spring body, excluding the hooks at both ends.

    - Overall length: the complete length from one end hook to the other, including the spring body and both hooks.
    - Free length: the natural length of the entire spring when no pulling force is applied.
    - Hook orientation: the opening direction and angle of the hooks, such as same direction, opposite direction, 90 degrees, or a special
      offset direction. Hook orientation affects installation and load direction.
    - Extension travel: how far the spring is extended during use. For example, if the overall length changes from 50 mm to 80 mm, the
      extension travel is 30 mm.

Force requirement: the force required at a specified extended length. For example, the spring may need to produce 2 kgf or 20 N at 80 mm. Descriptions such as “harder” or “softer” are only suitable for preliminary discussion; a quotation should specify the required length and force value.