We have a door-way that said server cabinet must fit through, measuring up at 620mm.
A 24" door? .. dang, that's tiny. Did someone mix up OD and ID when considering what a 19" rack meant?
1) Have you ever had to fit a cabinet through a doorway that's too small?
Yes. I will say up front that it's cheaper and easier to just buy one that fits (a knockdown, etc.) .. unless you're doing it yourself and don't assign value to your time, consider you'll be removing at least 1 stud, floor-to-ceiling, and any associated wiring that runs through it, along with the drywall on both sides. Refitting that, taping, sanding, painting, etc. If this is a commercial building and you're obligated to use tradesman, you've got at least 2 (carpentry and electrical), plus maybe a building permit, etc.
2) How did you do it? Cut cabinet, demolish wall ...?
The cabinet will be easier than the wall, but the wall will need less specialized tools (drywall work is easier than welding).
3) If you cut the cabinet, any tips?
Anything that will produce a weldable edge will do (sawzall, etc.) but consider that you will then have to grind the paint and fire up a mig welder (EMI issues) in your data closet, then grind (and paint) the results if you want it to look pretty. All I'll say about that is you'd better be darn sure everything is grounded. Also .. wear a respirator. Cutting/grinding the welds at the opposed corners top/bottom (to produce two triangular pieces that can swivel around and in) will be the easiest to weld back together (using a new triangular piece of steel as a brace if needed). If you don't know how to weld (and own a welder), or finish drywall (also harder than it looks) the costs associated with hiring out either of your two choices will easily equal just buying one that'd fit. Also, as someone else mentioned .. what happens next time it needs to move? Regards, Michael Holstein Cleveland State University