I need to drill holes for 4 standoffs in my case. I have a drill and a 6/32 bit, but I don't have a tap. Will I need to tap or can I just drill holes and use a plastic standoff like the ones for sale on this website?

http://70.169.170.235/acatalog/Motherbo ... doffs.html

I would think there is a chance that if you drill the holes then the brass screw in type standoffs will self-tap given the difference in softness between the two metals. It is a lot easier if you use a nut driver. This presumably is a Winmate mounting.

If you get the hole size right, Lodestar's idea will probably work. Honestly, when I'm faced with this problem, I usually just get a female/female standoff and epoxy it to the surface. It's ghetto, but you don't get points for style in my profession.

An alternative option would be to drill a through hole for the male/female standoff and put a nut on the other side

How long does the epoxy hold for? This will be a winmate mounting, so I will be plugging an ATX cable into it and there will be some play on the board from plugging things in, unplugging, power brick cable might get tugged accidentally. Is epoxy strong enough considering it would just be glued to a very small part of the standoff? I would be using 4 standoffs, but each one has a very small contact surface with the case itself.

I make no guarantees, but it generally holds to metal standoffs pretty well. If you use a female/female standoff and are generous with the epoxy, some will flow up into the thread and grab those. You can help by roughing up (with coarse sandpaper or a blade) both surfaces.

It depends on the epoxy (there are probably 100's of different ones.

It depends on the surface prep.

It depends on the difference in the coefficient of expansion of the two materials that are being epoxied together, and the temperature range that the materials will be subject to.

It depends on the magnitude and type of loads the joint will subjected to. Tension and compressive loads are best. Torsional or cantilever, not so hot.

Find a real source of stand offs. Look for something that has an outside hex shape that is internally threaded. That way you just ave to drill a hole in the case the right diameter to run a screw in from behind to hold the standoff to the case. Adhesives are very useful for many things, this isn't one of them.

I suggest you get some normal standoffs. Just drill a hole, glue the standoff onto the alu surface and use a M3 nut on the back side.

Plastic standoffs are a PITA to work with. Seriously.