SolidWorks has a feature that will create either a helix or a spiral, there is no need to create a 3D sketch and constrain a series of curves.
The only requirement to insert a helix or spiral, is a sketch of a circle representing the diameter. Begin by creating the sketch, when complete use the “Helix and Spiral” feature by expanding “Curves” from the CommandManager.
Select “Spiral” to create a spiral instead of a helix. The spiral generated will begin from the diameter specified in the sketch, to the number of revolutions input. Use “Reverse direction” to create an internal spiral. Alter the starting point of the spiral by using “Start angle” and set the direction of the spiral as either clockwise or counter clockwise. In the example below, a Ø50mm circle was sketched.
The other three options from “Defined By:” are used to define a helix. A helix can have either a constant or variable pitch.
This creates a helix with a single specified pitch.
The option to create a helix with a taper is only available when “Constant Pitch” is selected. The direction of the taper can be controlled using the “Taper outward” tick box.
Consider a compression spring where the first and last revolutions loop back onto the body. To achieve this type of helix, a variable pitch needs to be specified. For the purposes of the example, assume Ø10mm for the body and 30mm pitch otherwise.
To create a helix of the same height as the previous example, use the following parameters.
The first revolution will be from 0-10mm. The next two revolutions will be 30mm each, resulting in heights of 40mm and 70mm. The last revolution is 10mm for a total height of 80mm.
The result, after using swept boss/base is shown below: