I've only been able to find glass drill bits that drill up to a 1/2" hole. Does anyone know where to buy larger sized drill bits, maybe an inch & 1/2 to 2"???

I got my diamond hole bits on eBay. They're Chinese. Inexpensive (and cheap), but fine for drilling several holes before they die.

i had only found metric bits on ebay, that were inexpensive. Would a silicone seal around the bulkhead stop the water?

The ones i have gotten were metric as well, but you can figure out what you want in MMs and it's close enough. A bulkhead should seal on clean glass fine without any silicone, but i guess you could use it if you want.

I just watched a tank drilling demo on Sat and the guy doing it said that if you make a chip and are worried about the bulkhead leaking you can use silicone. He has drilled LOTS of tanks so I think he probably knows what he is talking about.

check out ameriglas.com (one s ) there really inexpensive and not bad quality.

I also wanted to add if you get chips, silicon carbide sand paper works great for ruff edges. I am a glassblower and have drilled many hoes. if you have any questions feel free to ask.

have drilled many hoes.

Dude, we don't need to know anout that. This is a family friendly site :rotfl:

twopartsolution (http://www.twopartsolution.com/index.php?main_page=index&cPath=70_71) sells a few diamond bits. Can't vouch for them, but I believe their sizes are appropriate for specified bulkheads.

oops typo, I just meant I do allot of drillin!