Ok this is how I would do it. There are more people here who have done this specifically on cases and may have better suggestions, but this is what I know how to do. There may even be plastic pop in standoffs or something which are easier to use. i personally don't know about them but someone might.
A tap looks a lot like a screw but it's beveled slightly and has a groove down one or more sides. It's what you carve the screw threads with.
They can be a bit expensive, but if you don;t want to front the money for something you will use only a few times, you can make a tap screw with a dremel. You need a screw made of harder metal than the case. Stainless should work, unless it really is titanium, in which case something else needs to be thought of.
find a screw that is the same as a mounting post. both in diameter and thread count. Length doesn't matter much as long as it's longer than the original screw. A local hardware (rather than a big box) should be able to both measure the mount post and sell you what you need. They may even have real taps or self tapping screws of the appropriate size you can buy. You will also need a bit of the same size as the thread barrel (the solid part)
If not, simply take the screw and carve a groove down the side. You are basically making a self tapping screw.
Just screw the tap screw into the hole you drill. use a hand tool, not an electric drill, you'll have more control. You want to put the thing in as straight as you possibly can, and do overs don;t generally work very well so be firm, and go slow.Edited by bombastinator - 10/14/13 at 9:49pm