LOAD TOLERANCES

A spring is a device for storing energy and it’s the force it produces that is normally the most important factor for safe operation. To ensure your springs are made and function correctly we always advise you to specify two load positions on any spring drawing (preferably the positions the spring will actually operate between in service).

By doing this you are automatically controlling not only the spring rate but also the spring free length (or free position in the case of a torsion spring). Free length should not normally be toleranced if 2 load positions are shown as 2 springs identical in length, diameter and number of coils will exhibit different forces due to subtle variations in material modulus and wire size / ovality throughout each spring.

We recommend standard LOAD TOLERANCES of ± 5% for both load positions (in some cases this can be reduced to as little as ±1%).

One important thing to note is that all springs with a load position in the pre-stress range of the material should be scragged (in the case of a compression spring; ideally compressed to solid length). This should happen before any load verification to ensure that any relevant PRESTRESSING has been carried out. This process will not only remove any permanent set, but ensures that the springs relaxation is reduced to a minimum.

Talk to us about tighter tolerances.