What is the elastic limit of a spring?

The elastic limit is defined as the maximum stretch limit of the compression spring without taking a permanent set.

It is a very common assumption that a compression spring would travel or can be compressed to its solid height. However, the compression spring has certain limit of flexibility considering its dimensions.

If the pitch between the coils of a compression spring is larger in proportion to its free length, and have loosely wounded coils, then the spring can be safely compressed to its solid height. However, if there is large pitch between the coils in proportion with a tight index, or the free length, there are all chances that the spring will be under high stress. This suggests that the spring will be stronger, but a compression spring elastic limit will allow it to travel to its solid height. Exceeding this limit will certainly result in spring taking a permanent set, which means it cannot return to its pre-loaded or free length, when the force is released. The compression spring elastic limits also depend on the type of material used.