How to make a ball capped screw? I am new to blender and I want to make an object that is a bulbous looking screw merged with a sphere at the top.  I can't seem to get it to work the way I want, because I am having trouble getting the screw to have an edge by which to extrude in such a way that I can then merge a semi-sphere on top of.
As you can see I do not have an ending of my screw that is perpendicular in the z-axis, not only they but it is only half a circle too (by design to get a smooth looking screw) but I believe I will need a complete circle to easily and smoothly merge into my semi-sphere (moved up in this picture, and I know it's a sphere now I left it as such for easier viewing)

Any help you can provide in achieving my goal would be really appreciated. Please let me know if you need any more information.
You can try to start with lower resolution. Like here is use Circle with 12 vertices. Screw mmodifier with 12 Steps, Screw 1.73.
Duplicate Circle and use as top sphere, just change Screw to zero.

I'm not sure how transition should looks like, but you can just use Boolean modifier &gt; Union ...
Before boolean, Apply Screw modifier, Merge by Distance 0.04 small inaccuracy. From top view box-select all center vertices and delete. So you get clean topology. Apply Boolean modifier. Loop select inner screw and mark as Sharp ⇧ Shift+E 1. Then add Subsurface modifier, Smooth shading. Under Data properties &gt; Normals &gt; enable Auto Smooth.

... or probably more natural it will result with upper part of sphere and manually delete unwanted faces and reconnect.