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Create a 3D spiral
The spiral commands of the 3D Curve menu offer methods to create three types of spirals in 3D space:
Conic spiral: A 3D spiral formed as though coiled about a cone.
Planar spiral: A two-dimensional spiral in 3D space.
Helix: A 3D spiral formed as though coiled about a cylinder.
Each spiral is defined by a number of parameters. The begin point of the spiral and the axis of rotation must be given; these imply the radius of a helix and the radius at one end of a conic or planar spiral. The number of turns determines how many rotations are to comprise the spiral, and the pitch specifies the distance along the axis between each turn (not required for planar spirals). Finally, the end radius of the spiral must also be given for conic and planar spirals.
1. The begin position for the spiral
2. The axis of rotation
3. The pitch (distance between each loop)
In the figure, the conic spiral and helix consist of five turns each, and the planar spiral was defined with seven turns.
To create a 3D conical, planar, or helical spiral,
1. Click 3D Geometry and then, in the 3D Curve group, click More next to Spline 3D.
2. Click Spiral 3D/Helix in the Direct section. The Spiral dialog box opens.
3. Type a name for Part.
4. Specify the type of spiral: Helical, Conical, or Planar.
5. Specify the axis with the Axis 3D CoPilot.
6. Click a point in the viewport to specify a start position (Start Pos). Immediate feedback shows the spiral curve.
7. Type the number of rotations in Turns.
8. Type the offset along the axis per turn in The pitch of a helix.
9. Type the final radius of the spiral in End Radius. This option is not available for helical spiral curves.
10. Turn Right-handed off to change the direction of the helical spiral.
11. Click to complete the operation.
 Pitch accuracy will be automatically adjusted to achieve better performance and minimum data size.