This video illustrates all the steps involved in making this 3D spring model
This is final rendered image of spring profile
And you will find complete video tutorial here https://www.youtube.com/watch?v=HxLBxDofRJ0
I selected arbitrary dimensions to make this model just to keep making this profile simple.
In a step spline has been converted to polyline before sweeping the circle over helix profile because it was returning error while sweeping on spline.