> Why is it that you want to remove those edges in the first place? Is there a specific goal you have in mind?

Vector output. Those vertical edges are not meant to be seen.

I actually did not model it myself. It's an internal screw thread generated with boltgen for rhino. I wanted to modify it for adding few more threads so I split the surface and added 3 more threads but now I can't get rid of those edges.

So let me ask like this; How do I add more threads to the attached model?