cutting laminated glass?

[NH-Rob]

My wife did stained glass for a while and I found that the glass breaks better with a light score than a heavy one. When I first tried to score it, I thought that if one swipe with the cutter was good, two would be better. The glass wouldnt break at the score when I ran the cutter twice and made a deep gouge line. Our instructor then told me that you just need light pressure on the glass cutter so that it leaves a V in the glass, too much pressure and the V gets a rounded bottom on it and takes the stress riser out. All you need is light pressure on the cutter so it makes a fine clean line. Use a good quality cutter and lub it with kero and light pressure and do both sides. The glass is only going to break from the side that it is scored, so you need to lightly bend the one side till it breaks then flip it and break the other side. Hope this helps. It works with sheet glass, but I have not tried to cut laminate glass.

I am going to try a lighter preasure while scouring and see if that helps. I think I will use a brush to put lube on the glass first too. I will not get to try it until Sunday because today is my aniversery and we are going out after work.
Rob

 

[crazyal]

I dip the cutter in keroseen first. I am using a new cutter that I got from ace hardware I think its a red devil or something. I have no problem cutting the laminated plastic the problem is just that the glass will not break. Does the preasure I put on the cutter make a difference? I have been using more preasure thinking the score line needs to be deeper but maybe thats wrong. Do you think the glass would snap easier if I heated the score line first?
Thanks for the help,
Rob

Less pressure is better. What you want is a nice fine line for the crack to follow, deeper is not better. You want to push just hard enough to score the glass in one pass. If you push too hard or try to go over the score again you'll make it the score will be uneven and as you try to crack the glass it may or may not follow the score.

Brush the kerosene on the glass, too much is not a bad thing. It'll help make the score smoother. You may want to get a piece of cheap window glass and practice getting the pressure right.

 

[crazyal]

I was watching the glass guys at work awhile back and that's exactly how they did it, they make it look easy.
I think what happens if you don't use heat to allow the plastic to bend and stretch is that when you try to bend it it won't because of the tension of the plastic. You end up cracking it from the other side where it's trying to compress. Dunno for sure it's just my guess....Mike

If you use a propane torch you have to be real careful you don't heat the glass up too much. Heat will make the glass expand and since there's two layers of glass it'll break. Like almost any job, the pros make it look easy because they've already learned the hard way what works.

Denatured alcohol is slower but will work just fine.

 

[forgeblast]

Saw this happen, watch too much heat will untemper the glass and it will shatter.
We were casting molten glass and as a test we left one piece out of the kiln, once it reached a certain temp it cracked and shattered. Slump casting glass is pretty cool too. the hardest part is having a kiln to temper it slowly.

 

[TBX500]

You should practice on a scrap piece first. Make several scores beside one another, do not go over the same score twice.If you do the cutter will be damaged. Dip the cutter in new motor oil before each score, just submerge the wheel of the cutter. Start pulling the cutter with enough pressure to make a continious score with out skipping, this is very important. If it skips the run will take off and not follow your score(thats bad) Now if it skips you need to figure out why, if it is rythematic every time the wheel gets to the same spot you need a new cutter. If it skips and then resumes you didnt keep your pressure. Now with a good score on one side you need to run(break) the score. If you are cutting less than

 

[Window Geek]

A couple of things, Rob. The lube, kerosene, should be painted on the glass AND dip the cutter in kerosene before you make your score. You need to lube the glass to improve the cutting. Lube the cutter because the carbide wheel will bind on the steel axle and cause skipping. When you cut glass, the wheel makes a microscopic fissure in the glass, literally wedging the surface of the glass apart. The lube on the glass helps fill in the fissure and helps the break to stay even.

Use light, firm pressure so that the glass cutter makes a hissing sound when you score. Pull the cutter toward you instead of pushing away from you. Keep the cutter at right angles to the glass surface. Don't press down so hard that you make glass chips spall off the surface.

After you score the piece, give it a full minute before trying to break it out. This give the kerosene time to fill in the fissure by capillary action and make your cutting easier.

Now flip the glass and cut exactly lined up with the other side, again, wait a full minute before you flex the glass. Flex the glass by keeping the cut over the edge of the table.

Don't use a propane torch. :shocked: Most laminated glass is annealed to be able to cut it. A propane torch will expand a small area of the glass (because of heat) and that difference in expansion forces the larger piece apart in random directions. (CRACK!) The guys at our shop use lighter fluid like for a Zippo lighter. Squirt a tiny amount along the scores themselves that little amount will soften the plastic interlayer.

Have you checked the number of layers of glass in this Laminated piece? If it's a triple layer, you won't be able to cut it.

Good luck,
Paul

 

[NH-Rob]

A couple of things, Rob. The lube, kerosene, should be painted on the glass AND dip the cutter in kerosene before you make your score. You need to lube the glass to improve the cutting. Lube the cutter because the carbide wheel will bind on the steel axle and cause skipping. When you cut glass, the wheel makes a microscopic fissure in the glass, literally wedging the surface of the glass apart. The lube on the glass helps fill in the fissure and helps the break to stay even.

Use light, firm pressure so that the glass cutter makes a hissing sound when you score. Pull the cutter toward you instead of pushing away from you. Keep the cutter at right angles to the glass surface. Don't press down so hard that you make glass chips spall off the surface.

After you score the piece, give it a full minute before trying to break it out. This give the kerosene time to fill in the fissure by capillary action and make your cutting easier.

Now flip the glass and cut exactly lined up with the other side, again, wait a full minute before you flex the glass. Flex the glass by keeping the cut over the edge of the table.

Don't use a propane torch. :shocked: Most laminated glass is annealed to be able to cut it. A propane torch will expand a small area of the glass (because of heat) and that difference in expansion forces the larger piece apart in random directions. (CRACK!) The guys at our shop use lighter fluid like for a Zippo lighter. Squirt a tiny amount along the scores themselves that little amount will soften the plastic interlayer.

Have you checked the number of layers of glass in this Laminated piece? If it's a triple layer, you won't be able to cut it.

Good luck,
Paul

Thanks for the help. I have not had much more luck and think I will give up and pay some one to cut it for me. If I come across a different brand of cutter with the oil in the cutter I might try it again. Maybe i should try to cut some normal glass and see if I can even do that first and yes the glass I am cutting is just two layers with plastic in the middle.
Rob

 

[tatra805]

my 2 cent on laminated glass

we have a sister company doing all kinds of glass coatings, i was a bit involved in the testing processes a couple of years ago and remember this.

There is a substantial difference between laminated glass and tempered laminated glass.

Tempered glass can not be cut. simple. The cutting happens before tempering.

I think you face this problem as all car glass needs to be tempered.

This is safety related: tempered glass breaks in the known small pieces while non tempered glass breaks in big parts leaving dangerous sharp pieces. compare a normal window to a car window when it breaks

The lamination is done for strength and isolation (sound) reasons in both cases. But does not influence the cutting behavior of the individual layers.


The idea mentioned here about heating the surface is to de-temper the glass in the cut area. From the tempering installations i saw i can only conclude it is a big gamble as you have no idea about temperatures, glass composition etc etc involved with tempering. ... Let alone that not every tempering reaction can be reversed.

good luck but i am afraid your 1 out of 10 is a good result already

 

[MtnViewRanch]

my 2 cent on laminated glass

I think you face this problem as all car glass needs to be tempered.

All windshield glass in the the USA is annealed laminated glass. Side & rear windows are usually tempered, some are tempered laminated. All are required to be some sort of safety glass. Windshields are not tempered glass of any kind. The reason for that is if it were to get broken while driving and it was tempered, you would not be able to see out of the windshield. Your windshield would instantly become obscure glass.

The OP is probably best off to have a professional cut the glass for him. It's easy after you've done it a few thousand times.

 

[tatra805]

MtnViewRanch, you are absolutely correct.

started the day learning something,... cant go wrong anymore

thanks!:thumbsup: