Make a spiral over contour


I need make a spiral over irregular contours.

In the image, I need make the spiral over the green contour. At left,  I do the  “Spiral” with offset command, after I need join de offsets.

At right there is a Spiral make with Spiral command, but I need that its path is over the contour.

There is any command or funtion for to do this?

Hi Manolo,

if i understand this correct, you can create the flat spiral large enough so it fully covers your contour. Then Split the spiral with the contour curve. To get hold of the spiral parts inside the contour, use SelBoundary, select the contour curve and invert the selection to remove all curves outside the contour.

does that help ?


I think he wants the thing to spiral inward following the contour - sort of like a spiral CNC pocketing toolpath… Rhino does not have this kind of function…


Hi Mitch,

i do something smilar very often with a macro like this

! _Repeat _Select _Pause _Offset _Pause _Pause _SelLast

But it`s not a spiral, it is an offset as shown in the above picture. @Manolo the offset distance it uses is the last distance entered in the Offset command.


1 Like

Thanks. It works fine

OK, I thought he wanted a real spiraling path…