madmaxthesniper

First of all, I selected the screws. They turned out to be about 2.5mm, but in inches. First of all, the fit test - will the screw hold with hole and thread I made?

Holds like a charm - proven on my mammoth and Warcraft projects as well.
Then I used Corel to make a circle and triangle inside - the markings of the holes, on the tips of the triangle. Circle itself happened to be 13.5mm in diameter:

You can see that the corner on 5 o'clock is already tapered. Then I simply and stupidly drill the holes with the drill diameter for the actual threading bit:

Then I use screws on both sides of... hmm, sides to keep them tougether, put round pieces to them and using pre-drilled holes to penetrate through the whole packet:

Using this technique you can hardly go wrong - whole thing stays tougether and does not shift during drilling, and the holes are for the actual pieces, so it fits like a glove.

Then threading the holes, keeping in mind that this is our only and last bit, if it breakes - you are... screwed:

Then widened the holes in round pieces for the actual screw sizes and make sure heads of the screws are sinked in deep enough:

HA! They fit like they were growing there. Next - shapng the sides to the circle shape of rounds. My English is so damn good, but how else to explain this? Capish? :)