Thanks for the warning Leslieann - would be easy to forget tools. You sparked the thought that it might be better to buy a wide MATX case and replace the back panel leaving the drive mounts. Could cut down and reuse the mobo tray too...
You're welcome.
Not only is it very easy to miss assembly tools, another problem I ran into was just plain missing holes. You can stare at something all day on a screen and not realize a screw is missing.
You can get a decent cheap caliper from Amazon or Ebay if nothing else. Cutting something down will certainly be easier, especially if you are not used to designing in cad, and often, even if you are and is much more likely to get a usable case your first time. There's a saying in manufacturing, plan on a prototype because you will make one anyway.
Which brings us to something else you may not have considered... Time and Cost.
Sheetmetal is not really expensive, but getting a shop to cut, bend and punch holes for you is. It's probably not too far off to say this would be AT LEAST $300 for your first prototype and that much for each thereafter, this being your first project like this, expect a few tries to get everything right (remember you don't have to redo every part every time, but it will still add up). Again the more you render the better your luck, but it's still easy to just simply miss things without it in your hands. A digital image is never as good as holding in your hands, I would budget for a few screw ups. Also, depending on the shop, unless you can get a shop to put a rush on it, it could be weeks or months before you get your parts, and then you have to make revisions and wait again. A few revisions and it could literally be a year and $1000 before you get the case you wanted.
So yeah, if you are willing to do this by hacking something, go that way if it will satisfy you, it will be cheaper and faster.
I have done what you are contemplating, taking a larger case and cutting it down, I put an ATX tray in an MATX case, cut down an matx case to make it smaller and cut an matx case into an ITX. It's not hard to do, but there is a trick to it.
Start with the sides.
I know, everything else seems more important, but the rest is actually the easy part, the hardest part is figuring out how to re-attach the side panels once you trim them. Remember most have hooks at the top and bottom, a tongue at the front and then screws at the back. If you start cutting that down, not only will the heat and trimming distort it (the folds keep it flat), but you are removing the attachment points. The first case I cut down I did the sides last and the flopped all over because I didn't plan ahead on them, the next time I figured out how to re-work the sides, then started cutting.
This worked for me twice now.
Tear down the case, leaving the front and top of the case connected, you don't want to mess up that connection. Trim the rear plate how you want, then trim the back of the top plate, then reattach those and trim the bottom. Now install the side panel, intact if possible, trim off the bottom, then on back trim it leaving 1/2in sticking out. Bend over the excess, drill your new mounting holes to line up with the old ones (use the cutoff as a template). By doing this the sides retain the front tongue and upper hooks so it sits flush. If your sides use a lower lip and no top hooks, you may want to base yours off the front lower corner instead, but beware the top of the side panel may not fit as flush, so it's best to use a top hook based case.
By the way, the guy not wanting to click through menus (Lars Christensen I presume) was referring to the drop down menus at the top . He's trying to get you to to use shortcut commands instead. While good (he does some of the better tutorials I've found), I personally found myself lost when he would use a shortcut if I didn't remember what it did or if I missed what shortcut he used. Again, shorcuts are great and they do speed things up, but they only help if you remember what they are doing, you need the foundation first in my opinion. That is one of my biggest gripes about cad tutorials, they often assume you know more than you do and they become outdated VERY quickly in many cases. "Click on ___" yeah, they removed that with the latest update. Ooops.
