I have noticed several comments about the difficulties encountered while trying to use thin metal boxes as equipment enclosures. Here is how I do it:
When installing jacks, switches, lights and controls in little mint and tea tins I often avoid using drills at all. A sharpened ice pick or other awl will poke a small (1/8" or 3 mm.) hole right where you need it and without tearing. Then use one of those little T-handled reamers to widen it out to the size you need. It will take you all the way out to 1/2". Clean it up with a small set of files.
Like pliers or adjustable wrenches there are no worries whether SAE of metric. Just fit and try. Without re-chucking bits and a whole lot of measuring the process is fast and easy. And cordless! You can purchase all these exotic tools at any cheapo tool supply, like Harbor Freight, for under $10.