Have the Phanteks P400a.  Never have drilled through a PC case before.  What is the best bit for it and do you need to worry about filings falling/flying into the Motherboard/PCBs?  Thanks.

You should use HSS Hi-Molybdenum bits and you can find them at your local Home Depot/Lowes and, while there, pick up a small can of cutting oil.  If you can’t get cutting oil, any light oil you have laying around will suffice.
 
Mark the spot you want to drill and use a center punch.  Start with a bit half the size you want for the hole to make a pilot hole.  Dip the end of the bit in the oil, drill the hole slowly.  As mentioned above, take your time and don’t overheat the bit.  Then move to the size bit you want for the hole and repeat.
 
The tape trick works, but with the tape, you can use your shop vac at the same time to catch anything flying off.  You are probably going to have to file some rough edges at the exit hole.
 
Having done mods on cases and other things, I personally would not do this with the anything in the case.  I tend to try to error on the side of caution since learning the hard way.
 
Hope this is helpful.

nateman_doo
I know it's scary to drill into a case for the first time, but once you get your feet wet, you will look back and laugh at this thread.  Good luck! 

Also, once you start, you'll start thinking and tinkering with other mods for your cases.  If you don't already have them, the next thing you know you'll be looking at Dremel tools and drill presses.

Wow those Hi-Molybdenum bits don't come cheap, but guessing they're worth it.
 
Thanks for all the tips and advice.  A plan is in action.

He heh good luck I once drilled into a psu and I told myself be careful there's a psu back there and did it anyway.  That plan was laid to rest along with All my adrenaline 😆A little anger management was in order