Spring Information
Helical (wound in a round shape) springs of round wire will need a discription to define the Coil Diameter, Wire Size, Number of Coils, and a Type of End. The Coil Diameter could be specified as an Outside(O.D.) , or Inside Diameter(I.D.) or even the Mean Diameter(average of O.D. & I.D. used for calculations). The Wire Diameter and Number of Coils may be defined in a way other than actually calling out the size and count, by a rate or known fixed load or torque requirement as example, but if known it is best to at least list as a referance.

Compression Springs
Known Load: If you have a known load you require at a known length this is the best way to specify the spring. If you also specify the free length of the spring(very common) then you have established a functional rate. The spring manufacture can use the coils that give you that load.
Rate: If you do not have or do not know the fixed place the spring is used, then specifying a Free Length and a Rate will give you a more consistant spring then specifing the coils.
Type of Ends: Compression springs can have four basic types of ends. Closed ends are almost always used in commercial applications. For many applications closing and addtionaly grinding the spring is used. This can give good squareness and better load tolerances but is often an expensive option, so should be considered but not always assumed. Here is a picture showing the four types.
   Closed Ends Not Ground          Closed Ends Ground


         Open Ends Ground       Open Ends Not Ground

Extension Springs
Known Load: If you have a known load required at a known length, this is the best way to specify the spring. If you also specify the length inside of the Hooks (very common like the free length of a compression spring) then you have established a functional rate. Now the spring manufacture will use the coils that give you the load you need. To go into further detail click the link to explore Extension specification

Torsion Springs
Position of the arms is very important.
Torsion springs are very difficult to communicate without a print or detailed drawing. For further details click the link for Torsion specification