Well, I took a break from building the hoods to drill the holes on my tank after getting the diamond bits in the mail yesterday. I drilled holes in a board to use as a template and taped the back side of the glass that I had not done before. I had read since my last drilling foray that it will help the chipping of the glass on the backside. The problem that I found with this is that it does not allow you to see the water starting to drip through the hole once you are almost through. The first hole was severly chipped and will require silicone, I removed the tape so that I could see the water drip through which told me to go very light on the drill pressure and the rest of the holes turned out OK.
New or Used it still has to hold water. Is silicone the best way to go about sealing the large chip that extends over the seal on the bulkhead or is there a better option for glass?
I have read of people using marine epoxy to fill-in the chip and then it works ok, but you may want to add silicon anyway, or just do silicon. So basically do what you feel is right.
Well, It took Blake coming by to suggest that I turn the bulkheads around so that the rubber seal would go against the smooth side of the glass rather than the inside chipped edge. I purchased several 1/2 inch rubber washers at Lowes and rather than turning around the bulkheads just added a second washer to the backside as well as the front. I used clear silicone as well and think that this will seal just fine. I went ahead and put the lock line in to see how it would work with the flow in the tank. I will wait a week for the silicone to cure and then fill it with water to test it. Blake took the bits to drill his tank, next week Norman and Marti will drill theres. If anyone needs the bits after that just let me, Norman (fisher12), or Blake (beanhead) now and we will get them to you.
Blake and I broke out the drill press and made a jig to hold everything down and went about drilling three 1 1/2 inch bulkheads. The actual bit size was 60mm or 2 3/8". There is no comparison to drilling with a press versus a hand held drill. There is not wobbling, variations in speed, ect. The only limitation to using a press is how far the bit extends out over the support of the press. This press is only a bench top model so the distance from the edge of the glass that you can drill is only about a foot or less. I imagine that larger floor press extend out quite a bit farther. The speed was set at 600 rpm (the lowest setting) and were careful about the pressure on the crank because Blake said the he had read that pressure on a press crank is a multiple of 7 times greater. Using a drill press is really the only way to go.
I think that after quit a bit of heart ache I am near the top of the learning curve with drilling glass. I purchased a replacement drill chuck for a hand drill at Harbor Freight for 5.00 and had a local machine shop thread a steal rod so that I can now put my portable drill anywhere on an aquarium and drill a hole. I also started using my portable hydraulic jack under where I am drilling that prevents to much pressure on the bit from prematurely braking through, which is what caused the awful chipping around the hole in the first pictures in this thread. I learned that to much pressure gets you nowhere faster when drilling glass and that it is most cost effective to use the diamond hole saw bits that you can get on Ebay for about 10.00. Just don't expect to get more than a half dozen holes out of them despite there claims. I will never use a portable hand drill again for drilling glass because one of the biggest dangers is torquing of the bit as it gets deeper into the glass. A 5 degree torque of the bit can ruin your day, yet I have seen Casey stand on a sheet of glass without breaking it - it is amazing the strengths and weaknesses that glass has. Beanhead is the only person I know that seems to have the magic touch when it comes to drilling glass with a hand held drill. If anyone would like to borrow the extension they are welcome to it.
