# Cutting thick tank glass



## fish_luva (Nov 24, 2009)

HI everyone, Looking for some pointers or methods of cutting really thick older tank glass.

I have a 125 gallon where the front pane is smashed and i am taking it apart to cut and use for some bracking on some larger tanks i'm going to reseal for when i redesign my fishroom. 

I have cut glass, for making tank lids with the proper scoring tool and snap..

Can you use this technique on This 1/4 to 1/2 thick glass?? I'm assuming it would be very very hard to snap and maybe not clean.

If there any other way to cut this glass that would work and with close tolerances.

Thanks for any tips...
sheldon


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## BillD (Jun 5, 2006)

Hi Sheldon. Thick glass is basically the same method just requires a little more force with the snap. If you can come out to the meeting on Tuesday, Jim Fowler can probably give you some useful advice. He has cut many, many (perhaps thousands?) pieces of glass, including the thick stuff. He cut a piece of 3/8" for me that was exactly the size I specified, and absolutely clean. He claims, as have others, that older glass cuts the same as new.


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## greg (Apr 29, 2012)

1/4" glass should be possible for those with limited experience. Ideally you will be using a good quality carbide cutter and cutting oil to lubricate the cutting wheel. Alternatively kerosene will work as a lubricant. A single score should be made with firm pressure.

Running pliers would be helpful. They are centered over the end of the score and are angled such that they push up from the center point under the score and down on either side of the score, causing the glass to snap and run along the score.

If you don't have running pliers then the usual technique to break 1/4" glass would be to lift the sheet from one end and snap it down on the straight edge of a table, such that the score lines up with the edge of the table. The longer the cut, the more glass you need overhanging the table to use this technique successfully. For example breaking off a 1" wide strip that's 1' long would not be possible for most with 1/4" glass using the table edge snap technique. In this case you would need running pliers. Or alternatively clamp the glass on the table with the score at the edge and then use some sort of pliers to grip and snap the glass along the score line. This may result in small sections of the score breaking at a time, leading to a rough edge that needs to be ground smooth.

Snapping/breaking the glass should be done fairly quickly after scoring, as the cut does begin to heal slightly, making it more difficult to break the glass cleanly.

Safety goggles and gloves should be worn.

1/2" glass is much more difficult and most would be advised to bring it to a glass shop. If you have excess glass however, then you can choose to try it at home. To break the glass you have the following options: running pliers, the snap technique of you can tap the underside of the entire length of the score repeatedly with the ball on the end of the cutter. This results in small breaks at the tapping point and is repeated until the glass has completely separated along the score. This last technique will result in a rough edge which will need to be ground down.

I have also read that 1/2" glass has been successfully cut with diamond edge blades for circular saws or diamond coated bits with a dremel. I have no experience with either of these techniques.

Hope that helps.

Greg


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## Fishfur (Mar 4, 2012)

I've never cut really thick glass, though I have some I would like to try cutting. It's mirror though, I'm afraid I will ruin it. One day I'll take it to the glass shop. Mainly I've done picture glass, as I used to build my own frames and completely frame pictures. I sure had problems with some old picture glass I tried to reuse, some of it tended to be very brittle compared to new panes. 

I have to say, though, that this may not be true of thicker glass, and may not be true of most glass. My problems could have been simply with the pieces I was working with. They were salvaged them from seriously ancient frames, so that glass might have been many decades old. Certainly some pieces were easier to work on than others.
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But unless you really want the practice and have some glass to spare, I'd take really thick glass to a glass shop. That way if it does not cut as you want, they are responsible, plus, if it has to be ground smooth, they have the machine and abrasives to do it quickly and neatly, where it would take you quite some time even with a power sander and the proper abrasives.

How long it takes to smooth the edge depends on what result you want when it's done - one that's merely safe to handle, or one that would suit the upper edges of a rimless tank. That kind of edge takes a lot more time and I'd rather have a pro do it, because of the time it would take me to produce anything like as good a result. 

If the edge is relatively smooth to start with, taking off the sharp edges is not much work. But any bumps or lumps could take a considerable time to level out. The kind of bumps you are likely to get if you have to use pliers to break off pieces on a long cut can be a lot of work to grind down. You also need the right abrasive for the job and preferably a power sander. For sure, wear goggles and gloves, you do not want glass slivers anywhere. Cloth backed abrasives will last much longer on glass edges than paper backed abrasives.


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## BillD (Jun 5, 2006)

I have had real difficulty with thin strips of 1/4" glass, as mentioned by greg. I found that tapping produced uneven results. Now, I score the glass, put the thin edge into my Workmate at the score line and snap off the large piece. This works very well. One thing I stumbled onto while doing some of this is that a piece of glass, could be a jar or bottle, rubbed along the cut will remove the sharpness, and do it more easily and quickly than an abrasive. Most sandpapers employ grit that are softer than the glass, and my experience using assorted sandpapers has been disappointing. A Dremel type tool, with a cylindrical diamond coated bit does a very good job taking it to the next step. The glass rubbing will make the edge safe, if not pretty.
As I mentioned earlier, I was told that old glass cuts as easily as new. I was cutting some old 3/16" glass with very uneven results. A carpenter, told me the problem wasn't the old glass, but me. He then proceeded to demonstrate a few cuts on the same glass, including some 1" strips, that broke off cleanly and easily when he did it. He was using a very cheap Richard cutter that he had replaced the wheel on, with some very small ones he had brought from Germany. However, I do believe that it was his technique that was the big difference.


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## Fishfur (Mar 4, 2012)

Nothing like experience at whatever it is you are trying to do. It's been so long since I last cut glass, I expect I'd make a right mess of the first piece or three, just getting back into the swing of it. But tools also matter. Having a decent cutter helps a lot. Cheap or costly, they do get dull and need the wheels replaced periodically.


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## BillD (Jun 5, 2006)

I did speak to the glass cutter about cutting thick glass. He said it can be iffy, and it has been a while since he cut 1/2" glass. He did say wear goggles and gloves. The procedure is the same as thinner glass. He prefers turpentine for a lube.


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