[Puzzdre]

Anybody, pls help me with this:

1. What diameter are the holes for holding the block to the mobo (I mean what dia I should drill through my block)?

2. Tapping (sp?) the holes - if I want to make the two halves of the block held together and reinforced with screws, like #Rotor have on his blocks, and if I want to tighten the halves with 3 mm dia screws, the question is - what dia should be the hole for tapping it to accept 3 mm screw? I found some taps (packed in 3 pieces, I presume that is for making initial thread with first, and advance in lateral thread depth with other two), but no info on what dia the hole must be for 3 mm screw. I know there are different kinds of threads, but this is something ordinary tapping set, sorry I didn't remember the thread size/step info from the box...

Pls. help!