Hello Michael,
I am stuck again.

I did my ring head as you suggested, with sweep instead of rail revolve.
Indeed that is the way....
However, As I am trying to finish my ring, (see pic), cannot perform the boolean diff to take away the additional part of the head....(see 3dm file).

Now, with rail revolve, I always finished everything (the whole ring) in few clicks...

Why that is happening?

Forgive my ignorance, but thought I had it....

Thank you,
Rudy

Hi Rudy, it looks like your sweep result is not closed, if you zoom in to this area a bit you can see a gap:





It looks like this is because your rail curve is made up of 2 segments that are not smooth in the area that they touch each other there, one way to smooth that out would be to select the control point where the 2 segments touch and delete it.

How did you create that rail curve? It looks like it might be the result of some projection or intersections between other pieces? Do you have the original pieces that were used to project or intersect with? Those original pieces may have a crease in between them as well.

- Michael

Hello Michael,
I deleted the point junction there, and...it works!

My rail curve is done as a freform going around the stone for the ring. I usually do half of the stone, then mrror the other half...reasons is that the cut is always a bit uneven, and instead of doing the whole perimeter by hand, resulting somehow less perfect, I mirror one half...the result is usually better.

Another trick learned to day.

I thank you very much.

Sincerely,
Rudy

Hi Rudy - no problem!

Just a bit more information for you here -

When you mirror something to make a full shape from a half shape, it can cause this kind of problem when the half shape does not have an ending direction that is exactly perpendicular to the mirror axis.

Here is an example where it is a bit exaggerated to help illustrate.

Here is a half-shape curve that I drew with the Freeform / Control points curve tool:




This curve is not going to be suitable for mirroring into a single seamless shape because of the shape it has at the end.

The ending direction is defined by these 2 control points:



If you imagine a line between those points, that is the direction of the curve at the end, like this:




To get a smooth mirror, that direction must be perpendicular to the mirror line, not slanted at any kind of an angle. So those 2 points have to be lined up horizontally like this:



The Transform/Align command can be helpful for editing points to line up horizontally like this.


Anyway that same situation is what was happening with your curve, although it was not such a large amount as in the example above so it was harder to notice.

But even a small deviation by just a couple of degrees can end up causing gaps when other things try to build and hang off from those curves like the sweep does. So it really helps to get those points lined up more precisely before mirroring.

In the future I would like to make some more automatic tune-ups to these kinds of things so that it would solve the problem for you. But it is a somewhat delicate area to make automatic edits that could change the shapes of your objects, I want to make sure that I don't do something that modifies them too much.

- Michael