Drilling Glass

R

robertifly

Premium Member
I recently drill 4 holes for 1" bulkheads and it went really very well except for one thing, where the drill came thru the other side of the glass the holes broke out a little instead of a smooth edge. I thought I went slow enough but maybe not. Anyone know what causes that problem? I have a couple more larger ones to drill and would like to get smoother holes, thanks.
 
I believe it happens because there is no support underneath the glass. When you are almost all the way through the glass the last little bit actually just breaks off. Let's say you could brace the glass from the inside, so that it is resting on a wooden support or something. This might help keep the glass from breaking through this last little bit. Does anyone else have experience with this?
 
ive had this problem it can be done just extreamly slow slow speed and very little weight from the drill. also try just drilling from the inside if possible and if you get a chip atleast its not on the gasket side.
GOODLUCK
 
i have done a repair with automotive glass repair kit from my local auto store. it did a good job of making a flat spot were the chip was on the inside of the tank for the gasket.
 
Did you constantly apply water while drilling the glass?It will help a lot for a smooth finish.I always take my tank to a shop in Orange County CA and the guy always put a ring,seal with silicone and put water with drill bit cooler gel in there and drill inside that ring with a drill look like a drill press but way smaller,the hole always smooth and perfect every time.
 
I have only drilled glass with a dremmel and diamond bit but from what I have heard if you angle it a little with back pressure from a wood block the water that is dammed up around the hole will drain in the one spot and you then know you are close to drilling all the way through. Then go even slower or lighter pressure. hope this helps.
 
I have drilled quite a few with a bit. Make sure that when you do it that you keep water going over the bit at all times. I usually do it in the backyard and have my wife hold the water hose for me or tape the hose in a good position until I am done. I still get a few small chips now and then but usually it is pretty smooth. If you want to smooth it some you can take a dremmel and go around the edge after you are done.
 
Yeah, I taped water hose in place to get constant water,,,maybe be the pressure right at the break thru point. Seems like I read where someone put tape on the back side but I'm not sure for what.
 
Tape is probably the best option for preventing this. It keeps the glass piece from snapping off prematurely. I believe AGA reef-ready aquariums are actually drilled from both sides of the glass simultaneously to prevent this.
 
i used some plumbers putty to make a ring around the hole im going to drill (like a donut with the hole in the middle) and fill the center with water and then start drilling. it keeps the bit cool the whole time. i tape the undersideof the glass to keep the piece from falling and causing break out.
 
I don't see how the putty dam could be better than a constant flow from a hose but I will use tape on the back side of the next two holes.
 
You can duct tape the other side, As stated before you need to be careful not to punch out the other side. When you close to the other side you need to take pressure off the drill. When you first cut through, the water will drain, if you can at this point you can turn the glass or tank and finish your cut from the other side. This will leave a clean edge.
 
point well taken reef96, I hadn't thought of that. I was doing mine on the dirve next to the shop and the hose was right there.
 
robertifly, I did this on my 6ft 150g, i put in a calflo style internal overflow box on one end of the tank making it a pennesula tank. I put in 3--1.5 in bulkheads, it took about 3 hours total to drill all 3 holes in .5in glass (that includes a few breaks by the way) i didnt want to carry that heavy thing anywhere else:)
and to think i was originally going to use a cpr overflow lol.

best decision in my build was to drill.
 
This is how I do it...clamp 1/4" acrylic front and back...I predrill the front acrylic so it acts as a guide and also holds the water for cooling.<br>
IM000946.jpg
 
reefer96, do you have another box on the outside for collection and plumbing or just plumbed drains right out of the BHs? I really like the calflo system, I had it on the last tank coast to coast and think it does a good job skimming, I am just trying to use it on this tank and use a BeanAnimal style Failsafe and Silent Drain system.
scaast, I did that but only on one side with a acrylic guide, maybe if I had one on both sides and clamped there wouldn't have been any break out.
 
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