I am trying to create a spline representing the top of a torx head screw, where torx tool will fit. I would then extrude. This will be where tool will be inserted.
We recently went to nx2, having great difficulty. help
It gives some limiting dimensions, but the dimensions of the small and large arcs are unspecified. Anyway, to draw it I would pick a size for the small arc and array it around then do the same for the large arc. Trim as necessary and use the geometry as is; if it really needs to be a spline you can 'join curves' at this point.