Making a hole bigger
 

I have a tank with 2 holes in the overflow, one is 3.5" for 2.5" bulkhead and one is 1.5" for a 0.75" bulkhead, I want to make the small hole bigger so I can use the herbie style drain. what is the best way to do that? thank you.

how thick is the glass?

it's about 5/8".

should be easy then, if it was thinner you'd have to worry about cracking.

I just did this exact thing on my sump with 5/8th glass. It was a 1 1/2 inch bulk head hole and now is a 2 inch. Bought the bit online mops something, came in three days...only took a rum and coke to deal with the screaming of the glass and tada a perfect hole over a hole. :)
http://img.photobucket.com/albums/v6...h1ca/016-6.jpg

what kind of rum? :D

The Captian keeps me straight LOL....
Ive done many a hole but this was my first hole over a hole... went better than most :)

do you need to have the glass wet to do this? and What type of bit? like a diamond tipped hole saw i'd imagine?

Yes, you well need to keep water on the glass while drilling to keep it cool. You will need a diamond bit made for drilling glass.

Michael Rice
Marine Engineers Aquarium Blog
Sent from Tapatalk so excuse my poor English

Cool I got one right! Lol