Drilling 90 Gallon Glass Question

Discussion in 'I made this!' started by MisterZJ, Aug 25, 2008.

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  1. MisterZJ

    MisterZJ Plankton

    Aug 13, 2008
    Birmingham, AL
    Hey guys! Everyone has been so helpful thusfar, so I wanted to ask one final question before I start drilling my 90 gallon tank. As some of you know who replied on my previous post, I am getting ready to drill 4 holes in the top back panel of my 90 gallon tank. I am going to look one more time thoroughly to make sure the glass is NOT tempered. I am going ahead and assuming that nearly 99% of pre-manufactured tanks come with a tempered glass bottom to prevent breakage from heavy objects. Now, from my research, MOST tanks do not have tempered backs or side panels. I have already read you can tell if it is tempered or not by several different tests. One is there should be some sort of dot or emblem saying "temp, do not drill" or something of the sort. Another is using polorized sunglasses to see if you see similar circles in the glass (like on your car windows). Don't make fun of this next "theory," but I used my knuckle and knocked on the panes of glass and the bottom panel DEFINITELY has a different sound resonating than the other panels. So, to the best of my knowledge, the other panels are not tempered. With all that being said, I have a question about hole placement. I am not worried about the two that are going on the outer corners of the tank. One on each side of the back panel for my returns. My question is for my two drain bulkheads. I am using a premade internal overflow that is actually the HOB overflow that is rated at 1200 gph with the backing cut out so it can be siliconed directly to the tank. This looks like it will be a very clean installation. But, I had one question before I started drilling. If I am using 45mm diamond bits to drill (all 4 bulkheads are going to be 1") how far APART should the two drains need to be to prevent breaking the glass? I have a limited distance to work with, and obviously I would like to position them as far apart as possible while still fitting behind the overflow box, but is there a minimum safe distance, etc?? Have any of you drilled two holes close together? Any special advice for that situation that differs from the common advice of "let the drill do the work and put almost no pressure at all, take your time, and keep plenty of water flowing across the bit?"

    Any opinions and advice would be greatly appreciated.

    Thanks in advance,

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  3. Iraf

    Iraf Snowflake Eel

    Jan 20, 2008
    Tulsa, Ok
    http://www.youtube.com/watch?v=GSYqSeW1mQg kind of a rough overview on it. I think the general rule is you don't get bulkheads within their own width of each other, so a 1" bulkhead leave 2" between them minimal, ect
    Last edited: Aug 25, 2008