So you just need a 10mm diameter counterbore for the head of the cap screw? are the parts in your model solid components/groups? If so, draw a 10mm dia. cylinder and make it a solid component or group. Position it in the part to the depth of the counterbore and use Subtract from the native Solid Tools or better from Eneroth Solid Tools to make the counterbore. Think of the cylinder as a drill.
Explore all the Tools that don’t show at startup. The ones that show are indicated by a check mark. You can customize the Tools Palettes and they will show up the next time you start SketchUp.