General Information

Although various springs require different design techniques, types of material and manufacturing processes, there are a few general things to be said about most mechanical springs. One should consider the environmental conditions in which the spring will operate, its specific load-deflection requirements, frequency and velocity of load application and the required life span under the specific working conditions.

Predicting spring life is not an exact science and must be carefully considered in all stages of design and consultation with the spring manufacturer. No matter how much time, effort and money is spent to insure long life, it is practically impossible to guarantee that there will be no failures in a given production lot of springs under severe operating conditions. However, the life expectancy of a spring can be extended by careful design and selection of material, as well control of both material and manufacturing.  

This is one of the most neglected factors which can adversely affect overall spring performance. Microscopic corrosion is often the source of spring failure yet its presence often times goes undetected as the cause of failure is erroneously attributed to other causes. Passivation is recommended for maximum corrosion resistance for stainless steel while most other uncoated steels must be given some kind of corrosion protection.

As cost is a major consideration, springs must be produced in the most economical manner. Specified tolerances should be generous enough to permit the fabrication of acceptable springs by ordinary production methods. Also, it is wise to apply tolerances only to functional requirements and dimensions. This practice gives the spring maker an opportunity to make adjustments to compensate for the allowable variations present in the size and mechanical properties of all spring materials. 

Burrs are considered undesirable, so some draftsmen include a note on all drawings reading, “Remove all burrs”. This can result in additional cost without adding value to the part. Burrs are produced, to some degree or other, by many of the operations used in manufacturing springs. Burrs arising from other operations may sometimes be controlled, within limits, as to size, shape and location. When the spring maker and the spring user can agree upon such limits, an opportunity for significant savings is created.

Whenever a carbon steel is pickled in preparation for plating or during some electroplating processes, hydrogen can become absorbed into the material. The hazard of hydrogen embrittlement becomes more acute where there is (1) high stress, (2) high Rockwell hardness, or (3) high carbon content. Tempered carbon steels are more susceptible to hydrogen embrittlement than cold-drawn carbon steels at equivalent hardness levels. There is no quick check for hydrogen embrittlement. To relieve embrittlement, the springs must be baked immediately after plating to drive the hydrogen out of the material.