Adding meshes onto an existing mesh Follow up of:
How to remove duplicate verts after spin tool?
How can I add bolts onto an existing mesh? If I create a separate object (as a single bolt) and duplicate it so that it looks like the inner part of the rim (ITALIERI) below:

how can I merge them with the existing mesh so that there are no ngons? Additionally, the new vertexes will also inherit the subsurf, right? meaning that each needs an  extra edge loop or crease.
Just add more loopcuts to have enough verts and then connect a circle.

Add more loopcuts and make a hole in the mesh
Position the 3D cursor there (Mesh &gt; Snap &gt; Cursor to selected)
Add a circle with proper number of verts and connect it