nice disco amp head!
i'm trying to build a cab using mdf without having much of a clue about anything, or reading up about things beforehand 
the mdf split up in a few places where i put screws, but when i glue it together and use clamps during that process i hope it'll get better
I'm planning to prime it and sand it a bit, and then paint it some darkish color, haven't decided what yet.
no money/skills/patientce for tolex. grill cloth is some crap i got cheap from aliexpress. it works.
if i'm going to run in to problems, advice is much appreciated.
The problem is that the core of a sheet of MDF is extremely soft, and very weak. The trick to screws in MDF is to drill pilot holes which are fairly oversize, and to flood the area around the hole with cyanoacrylate (super glue, frequently known as CA). As much CA as you can get it to absorb - though you don't want it to start filling the hole. For instance, in soft wood a #8 wood screw should have a 5/64" pilot hole, and 7/64" in hard wood. The nominal diameter of the shaft is .164", which is a bit more than 5/32" I would drill a pilot hole with either an 1/8" or 9/64" brad point bit, and then dump a bunch of thin CA into the hole and around the perimeter. Let that soak in for 10-20 seconds, then hit it with a shot or two of accelerator. Go slowly when you are driving your screws. You can try using some cauls and clamps to support the hole when you are driving the screws, but it probably won't help.
After it has cracked, you can try disassembling the piece; then gluing and clamping with either wood glue or CA (make sure you use cauls to spread the force of the clamps, and wax paper to keep the cauls from sticking to anything); and then enlarging the pilot holes and hardening the MDF with CA (if you don't, it will just split again), but there is no guarantee it will work, as the core of MDF doesn't really take glue all that well (it is so porous it just kind of soaks up the glue without really bonding).
Honestly, though, with out some kind of support (either cross dowels or threaded inserts), MDF is an awful material to try and use with screws. All the strength of MDF in in the outer skins, and they are so hard that if you try to drive a screw into them with out a very large pilot hole, they just shatter.
Gabriel
