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Old 07-17-2020, 06:58 AM
touringgarage touringgarage is offline
MetalShaper of the Month September 2014, April 2019
 
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Default Windshield Cutting

Still a mystery to me how laminated Windshields can be Cut afterwards.
Does anyone here have Experience.
Thanks

Bernhard
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Old 07-17-2020, 08:03 AM
Mr fixit Mr fixit is offline
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I have a similar question, and some of the answer, maybe. The question is do they cut it before it is tempered or do they order them without tempering, the reason safety glass brakes into small crushed ice form is tempering, which can not be cut at all vs large pieces like a broken mirror or the window at home.

The way safety glass for windows like store fronts, school doors etc. is it is cut on both sides and then you brake the cut, then burn with alcohol the inner plastic layer and cut it at the same time.
This is what I see our glazier do at work.

I too have a rear window that is unobtainable and want to have one done, but not sure how to go about it or even find a shop that will do it. Any suggestions would be greatly appreciated.

TX
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Old 07-17-2020, 09:05 AM
billfunk29 billfunk29 is offline
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Default cutting windshields

Windshields are not tempered. They are a lamination of two layers of glass with plastic sandwiched in between. It can be cut a number of ways; Sandblasting, diamond saw, or old style metal roller blade. Once the glass is cut down to the plastic,on both sides, put alcohol in the gap and light in on fire. After it burns out, use a knife to cut the plastic. Then grind the edges with a diamond abrasive disc.


Youtube has videos of all the methods.



That said it is a touchy process with less than 100% yield.
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Old 07-17-2020, 09:05 AM
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Kerry Pinkerton Kerry Pinkerton is offline
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TEMPERED glass like side windows cannot be cut.

Laminated windows like windshields can but I've never done it.

Two approaches I've read about in various magazines back when magazines covered real people doing work instead of articles which were nothing more than product placement ads for their advertisers:

1- Score both sides with glass cutter, pour alcohol in crack and light it to soften the glue between the pieces. Break apart. Using a glass sanding belt, finish the edge.

2- Cover glass surface you want to keep with rubber mat, tape securely to the cut edge. Sandblast through the first layer, cut the membrane, score and break the other side. Using a glass sanding belt, finish the edge.

3- Probably many more

I repeat. I've never done any of these.
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Old 07-17-2020, 09:17 AM
billfunk29 billfunk29 is offline
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Default Tempered glass

Most tempered glass is done chemically. The chemical decreases the Thermal expansion of the glass on the outside. As the glass cools the inside is in tension and the outside in compression. Glass won't crack in compression and cracks need to start on the outside. So, much stronger glass. Unless you poke a hole in it. Sort of like a balloon, it will explode. Since the process involves a chemical change, there is no way to "anneal " the stress out with heat. No way I know of to cut tempered glass.
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Old 07-17-2020, 09:36 AM
Marc Bourget Marc Bourget is offline
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Side note.


Orlando Cairo in Ft. Lauderdale makes "custom" windshields for out-of-production Sports cars and race cars originally equipped with plexiglass.


He makes a form of 1/4 mild steel - final polish is critical and sends it to a glass factory for forming.


FWIW
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Old 07-17-2020, 12:46 PM
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heinke heinke is offline
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Default Cutting laminated windshield glass

Ah, a topic for which I do have first hand experience. My experience is project based (i.e. I'm not a glass professional) and thus is limited but relevant. For example, just this week I successfully altered a tempered glass side window by removing some material.

For laminated windshield glass, there are multiple techniques but they all come down to 2 basic methods: controlled cracking and grinding away material. The traditional glass cutting technique of score, crack, and split is really just controlled cracking (unless of course the crack wanders away from the score then it's a ruined piece of glass ). I've seen this done first hand and it's by far the most time efficient technique. It does require the softening and cutting of the laminate.

The one I've done firsthand is the grind away method via a diamond encrusted router bit and Rotozip tool. With this technique, you're slowly grinding away the glass around the desired edge under a mist of coolant. Both layers of glass and the laminate are getting ground/cut away at the same time. The Rotozip motor is being held freehand, cutting goes very slow so you need a very steady hand and lots of patience to even think about using this technique.

For my Ferrari 250 GTO project, I elected to use a 1960 Chevy Impala windshield shape. The original GTO windshield is highly curved and with the top and sides cut off the Impala glass resulted in a similar curved shape that also has the increased 6" width in my GTO over original. Bottom line, the car has a polycarbonate windshield in it now as there was never a successful cutting using either the above methods after many, many attempts.

I believe there's several factors that play into if laminated glass can be cut:

1) quality of the glass. I could only source new windshield glass that was made in either China or Mexico. There just wasn't any US or EU made windshields available. The glass professional that tried to cut the Impala windshield via score method swears his cutting yield percentage has dropped significantly since US made windshields have become unavailable.

2) amount of curvature in the glass. I could repeatedly cut the sides off the windshield without cracking it but cutting the top off always resulted in an unwanted crack. This was true for both methods of cutting. The top had the greater curvature and more compound curve. I believe that once laminated, the resulting glass was left with a great deal of stress/tension within it. When cut, the equilibrium within the glass is disrupted resulting in a crack that wanders through the stress area. Less curve equals less captured tension and thus less likely to crack when cut.

So while cutting the laminated glass didn't work out for my project, I do know it's possible. My recommendation is to find a donor windshield that's close enough without cutting. If that's not possible and cutting is required, expect you (or whoever does cutting for you) will break a few windshields before being successful. If you do go down the cutting path, I'd recommend you successfully get one cut before the project is locked in to that particular shape of glass. Otherwise, you might end up having a polycarbonate or other such material there in the end.

I can post my experience with tempered glass if someone needs it. Just speak up.
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Old 07-17-2020, 01:16 PM
Chris_Hamilton Chris_Hamilton is offline
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Some links and videos,maybe someone will find it useful.

This guy does a lot of cutting and has lots of patterns if you need something made.
https://www.jalopyjournal.com/forum/...ldwide.614524/

Pete Hagan cutting a laminated windshield:
https://www.youtube.com/watch?v=pl5nm48pYFc

Custom glass manufacturer (mainly boats but can do it all)
https://www.procurveglass.com/
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Old 07-17-2020, 01:16 PM
John Buchtenkirch John Buchtenkirch is offline
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A way to cut curved windshields. https://www.youtube.com/watch?v=pl5nm48pYFc
And another way. https://www.youtube.com/watch?v=Wf63WOLvxAc
Iíve never been able to cut glass so this always fascinates me. Enjoy ~ John Buchtenkirch
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Old 07-17-2020, 03:18 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by billfunk29 View Post
Most tempered glass is done chemically. The chemical decreases the Thermal expansion of the glass on the outside. As the glass cools the inside is in tension and the outside in compression. Glass won't crack in compression and cracks need to start on the outside. So, much stronger glass. Unless you poke a hole in it. Sort of like a balloon, it will explode. Since the process involves a chemical change, there is no way to "anneal " the stress out with heat. No way I know of to cut tempered glass.

Waterjet works.
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