Step 7: Drill Baby Drill
To do this I first lined up everything inside, then marked where I wanted to drill on the outside.
Drilling Altoids tins is easy. Just be careful. Get a good RPM going, press some, and make sure your fingers are safe. You may want to file the inside of your tin if you've got lots of metal bits poking things. (I didn't, but you never know.)
It also doesn't hurt to have a backup tin around. Just in case.
Make sure your headphone jack goes all the way into the drilled hole! If nothing else test that your headphone will in fact work with how you've got it set up!