Conical Extension Springs
Conical extension springs are designed and manufactured by coning down the last few coils then forming the hooks on these reduced ends. The main purpose of this type of spring is to decrease the stresses in the hooks, thus avoiding breakage.
Another advantage of this type of spring is the ability to create swivel hook extension springs, which are manufactured with separate “S” hooks that are inserted inside the reduced ends.
These types of hooks enable free movement to ensure the correct alignment for the application. In larger wire diameter extension springs where loads can be significant, the ends may be coned down in order to fit in plugs or even large eyebolts.