I did some case-modding on my C64 breadbin. All written on my blog here:
There are two type of brass standoff’s for PC motherboards. Those with a thick screw, and those with a thin screw.
Here’s a picture of, from left to right, two #6-32 UNC and an M3 screw. (The fourth is a self-tapping screw used for mounting case fans.)
A great tip for mending cases and/or rebuilding missing bits is super glue and baking soda. The fine powder instantly hardens the glue and produces a very sturdy compound. It’s even sturdy enough to rebuild broken pins (which serve as a hinge or pivot of sorts) or to mend broken cog wheels! (To rebuild a pin, just add a tiny drop of super glue using a needle and drop some baking soda on this, in consecutive steps.)
Since the resulting compound lends itself to sanding quite well, this could be even used to rebuild complex structures, like broken grills. And it takes some stress quite well! So it may be also used to harden parts that are apt to breaking again. (E.g., I’ve an Olivetti M-15, which tend to have a broken hinge and often cracks from the stress applied by the spring loaded hand screws, which are tightening and arresting the screen. So was mine, and it was an easy fix. – Also very useful to repair broken tabs and case hinges for those tabs.)