Extension Springs


Extension springs are helical springs that exert a force when extended and are subjected to torsional stresses. They are usually cylindrical springs with hooks or some means of attachment on the ends.

black machine hook extension spring

The most common end is a machine hook (part of the coil is bent at 90 degrees to the body to form the hook) Hook opening is usually specified according to what it must fit over. Sometimes the springs have a reduced diameter at the end to accommodate a smaller hook radius dictated by the stress levels in the part. Hooks are subjected to bending stresses and must be a part of the design considerations.

Other types of ends used are Swivel Ends or Plugs (which can screw into the spring)

Extension Springs will often be specified with a Spring Rate and/or a Load at a given extended length. Some will even specify 2 load points with applicable loads at those lengths.

Extension Springs may or may not have Initial Tension. Initial Tension is possible and very common in Cold Wound extension springs. It is impossible to achieve Initial Tension in Hot Wound extension springs.

Unlike Compression Springs, Extension Springs cannot be designed using a variable rate.

Finishes on an extension spring are usually specified as either plain finish or dip painted.

Any type of spray finish, whether paint or powder, will not get between the coils or on the inside diameter of the spring

Trust RMW Industries Inc. to manufacture quality extension springs.

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