I have followed this video from Lynda http://www.lynda.com/articles/dekes-techniques-drawing-a-perfect-spiral-in-illustrator to try and make a perfect spiral for a logo I am working on. I've done each step but when it comes to the part where I actually bring the bottom lines to join with top ones Illustrator keeps jumping so the lines wont meet. I've looked at the incremental settings incase that was the cause but that is set at the very lowest (0.01 pixels). I've tried turning on and off the "snap to point" option but that doesn't make any difference.
This is as close as I can get and if I move it again it just jumps to the other side....
Given what you've tried it sounds like its a very small spiral. Scale it up, position them, then scale it back down.
Hum. I am afraid that is an incorrect aproach, regardless if the tutorial says it is a perfect spiral.
The error is that that figure has a "Jump" in the diameter every half circle.
A "perfect" spiral has a smooth continous progressive increment in diameter. Your specific model is an Archimedean spiral.
That can be minimimized using smaller fractions, for example every 90Â° make a smaller jump.
1) A real quick solution for the type of spiral you are drawing is that you install Inkscape which is free and use it to generate your real spiral.
2) There is another type of spiral called logaritmic spiral which is the one you see in sea shells https://en.wikipedia.org/wiki/Logarithmic_spiral
If you need the logarithmic one, either you use this diagram as a basis to draw one. Extend the number of circles as you need
or if you have a PC, use the 30 day trial of CorelDraw which has a tool to create this kind of spirals in one click.
3) If you want to stay with your aproach Join the segments and fuse the nodes. (In fact, your spiral is not one but two spirals)