# How to make all selected edges parallel to one axis?

If I have multiple edges selected, how can I set them all parallel to the x-axis?

Example:

I want to make all of the inner edges in this "tapered screw" parallel to the x-axis so single inner edges don't have different y- and z-values for it's two vertices.

Setup for my situation:

1. Create one edge in x-y plane, parallel to x-axis (created plane and deleted two vertices)
2. Add Screw modifier around x-axis
3. Add Simple Deform modifier, set to Taper
4. Apply modifiers
5. Desired outcome: Screw taper has all edges parallel to x-axis (instead of vertices having varying y- and z-values on single edge)
6. Proposed solution: Hide screw outer edges and select only inner edges. Make all inner edges parallel to x-axis. How can I achieve this?

I'm hoping to avoid the brute force solution of aligning each vertex to its edge pair vertex by setting origin to one vertex and scaling y to 0 for the pair.

The Taper is scaling the far end of each X-edge more than the near end. One fix is not to give it 2 ends to work with; just a single vertex.

• Start with a single vertex, away from the object-origin in YZ.
• Screw and Taper as you did before,
• And then apply the modifiers, and extrude the spiral of edges in X.

Or you could go entirely procedural, @Gorgious-style, not apply the modifiers, and do the final extrusion with another Screw modifier along X, through 0 degrees, 1 iteration, with a 'Screw' value of your desired X-edge length.

The lower copy has had its X-edges selected by ShiftG Select Similar > 'Direction'

• Very nice solution…👍🏻 Commented Aug 15, 2021 at 9:43
• @Chris Thanks! But I've just noticed friendoflore might want the screw pitch to reduce along with the diameter. This may need to be tweaked. Commented Aug 15, 2021 at 9:50
• This fits beautifully, thanks a bunch! No tweak required for my use case
– moth
Commented Aug 15, 2021 at 10:43