How to Make Apple’s Mac Pro Holes

The hemispherical holes are milled into both sides of the plate, but the holes on the other side are offset so the hole centers on one side fall exactly in the middle of the triangle formed by the hole centers on the other side:

You already know the horizontal offset for the centers from one side to the other is x, but how far up do you go to hit the center of that triangle? So let’s turn this around, and summarize by saying for a plate of any thickness t, use:

Where r is the radius (half the diameter) of the spheres and 2x is the horizontal spacing of the sphere centers on a given row. So to CAD this up, all you need to do is start with a rectangular block of thickness t, and use the formulas above to place the centers of the spheres (with diameter 2r) on the front and back of the block.

Source: saccade.com