How to Cut Your Curved Windshield When Chopping The Top

[david58]

[SCOTTRODS]

How Cool is that?

What "other ways can we cut our glass?

[david58]

And everyone says it can't be done.

[SCOTTRODS]

And everyone says it can't be done.

I've heard of folks sand blasting the glass away as well.... not that I'm sure I think it's possible,... but hey.... They can cut rocks with water nowadays.... so ya never know.....

[Marc]

And everyone says it can't be done.

There's a big difference between cutting laminated safety glass (I've never heard anyone say that it can't be done) and trying to cut tempered glass...

http://www.shoptalkforums.com/viewtopic ... 43&t=78329
http://www.newportglass.com/temper.htm

[SCOTTRODS]

And everyone says it can't be done.

There's a big difference between cutting laminated safety glass (I've never heard anyone say that it can't be done) and trying to cut tempered glass...

http://www.shoptalkforums.com/viewtopic ... 43&t=78329
http://www.newportglass.com/temper.htm

I know about tempered Glass..... I was just wondering about the Blasting type cutting of glass.... doesn't seem like a great idea to me, although there are indications that folks still do it. The video shown is probably the best way I've seen it done so far.

I used to re-glaze windows when I was in my early 20's (47 now) and loved me some Tempered glass..... Easier to sweep up than Normal Glass was. and a lot less dangerous to your hands in almost every way. (gloved or not,... glass is dangerous stuff.)

[Marc]

Did you read the Newport Glass article I linked above? Yes, you can cut heat-tempered glass by sandblasting...and NO, you shouldn't.

"Fully tempered and heat-strengthened glass cannot be cut after tempering. Chemical tempered glass can be cut but the cutting process causes total loss of the added strength within one inch of the cut. It is not advisable to sandblast, acid etch or grind the glass after tempering because the surface compression layer may be weakened or penetrated thus causing spontaneous breakage."

But this is irrelevant when discussing windshields, because you wouldn't want one made from tempered glass - if it were to catch a rock it'd break into thousands of tiny pieces that'll blow in on you. If they stay in place it's even worse since you can't see a thing. Windshields should always be made from laminated safety glass, and that's no big deal to cut.

[Steve Arndt]

I had my front window cut down. Cost me 25 bucks to a bro. I rolled my car, and didn't get the window frame quite equal on each side during repair. I broke three windows before having one trimmed down. They would install easy, then the next morning they were cracked. Just too tight.

[SCOTTRODS]

Did you read the Newport Glass article I linked above? Yes, you can cut heat-tempered glass by sandblasting...and NO, you shouldn't.

"Fully tempered and heat-strengthened glass cannot be cut after tempering. Chemical tempered glass can be cut but the cutting process causes total loss of the added strength within one inch of the cut. It is not advisable to sandblast, acid etch or grind the glass after tempering because the surface compression layer may be weakened or penetrated thus causing spontaneous breakage."

But this is irrelevant when discussing windshields, because you wouldn't want one made from tempered glass - if it were to catch a rock it'd break into thousands of tiny pieces that'll blow in on you. If they stay in place it's even worse since you can't see a thing. Windshields should always be made from laminated safety glass, and that's no big deal to cut.

Yes,.... Read the linked stuff.... but it also says cutting "CHEMICALLY TEMPERED" glass is possible.... heat tempered ain't happening until it's annealed... then you might as well just have one made from scratch, and tempered. But with enough money anything is possible, right? Hotrodders and car customizers are just a bunch of guys trying to do the Engineering on a tiny budget.

I love the term "Spontaneous Breakage".... Reminds me of Spontaneous combustion....

[Marc]

.... Read the linked stuff.... :

Evidently not very thoroughly.
"Chemical strengthening is used for certain optical application or on glass sheets that have a thickness of less than 1/8 inch."

Because heat tempering is generally ineffective on glass <1/8" thick, chemical strengthening is used as an alternative for the thin stuff. If it was done to a thicker sheet, you wouldn't want to use chemically tempered glass for car windows anyway - it's stronger than regular glass, but when it breaks it's more likely to become jagged shards like regular glass rather than relatively harmless "dice" like properly heat-tempered glass. And as already mentioned, there's a total loss of the added strength within ~1" of the cut edge.

[SCOTTRODS]

.... Read the linked stuff.... :

Evidently not very thoroughly.
"Chemical strengthening is used for certain optical application or on glass sheets that have a thickness of less than 1/8 inch."

Because heat tempering is generally ineffective on glass <1/8" thick, chemical strengthening is used as an alternative for the thin stuff. If it was done to a thicker sheet, you wouldn't want to use chemically tempered glass for car windows anyway - it's stronger than regular glass, but when it breaks it's more likely to become jagged shards like regular glass rather than relatively harmless "dice" like properly heat-tempered glass. And as already mentioned, there's a total loss of the added strength within ~1" of the cut edge.

What did I miss? None of that ^^^^ says anything about what I said, being "wrong" or even "not well read"? I am pretty sure I read all of it and understood it fine.... Please enlighten me.....?????? I'm good with being corrected, but let's not be too subtle... I like the "hammer to the head" versions of corrections. I'll understand it better and remember it much better as well.

[Marc]

Yes,.... Read the linked stuff.... but it also says cutting "CHEMICALLY TEMPERED" glass is possible.... :

I took this to mean that you hadn't given up on the idea of trying to cut tempered glass and were encouraging the idea of acquiring a sheet of chemically tempered glass to cut windows from - that would not be acceptable, nor would having plain glass chemically tempered after cutting.
If that's not what you were implying, I apologize.

I'm just trying to put this subject to rest - the ONLY satisfactory ways to make car windows are from laminated safety glass or polycarbonate ("Lexan"). Side and rear windows can also be made from plain glass provided it's properly heat-tempered after cutting, or from acrylic ("Plexiglas") although I wouldn't recommend the latter for street use.

[SCOTTRODS]

Yes,.... Read the linked stuff.... but it also says cutting "CHEMICALLY TEMPERED" glass is possible.... :

I took this to mean that you hadn't given up on the idea of trying to cut tempered glass and were encouraging the idea of acquiring a sheet of chemically tempered glass to cut windows from - that would not be acceptable, nor would having plain glass chemically tempered after cutting.
If that's not what you were implying, I apologize.

I'm just trying to put this subject to rest - the ONLY satisfactory ways to make car windows are from laminated safety glass or polycarbonate ("Lexan"). Side and rear windows can also be made from plain glass provided it's properly heat-tempered after cutting, or from acrylic ("Plexiglas") although I wouldn't recommend the latter for street use.

Oh.... I see..... LOL I guess that could be misconstrued that way.

No... I have no intention of trying to cut Tempered glass after a very basic knowledge during my window Glazing years.... I rather like the whole concept of laminated Safety Glass best.... If you can find a piece that will match the form you need to fill, I'd recommend it over the Tempered DOT glass..... I have never thought it would be a good idea to cut tempered though. I have heard of Cutting Windshields and Really liked the tutorial Video. I was just commenting on that Chemically tempered glass remark in the Link you supplied - Very good info for those who have questions for sure. As far as clean up,... Tempered all the way... but not for cutting.

Back in my A&P days, I got schooled on the Polycarbonate windows.... Knowing what a piece of it cut and polished out correctly can handle is a strong selling point. I have seen some pretty nasty Airplane Windows "Micro Meshed" into optically clear panels.... And they were still serviceable too. Great Stuff. I don't know if I'd want to mess with anything else for a custom build that includes chopping the top. Maybe a Windshield, but not the other pieces.

I went back and looked at the other threads you linked to as well.... I understand further why my comment brought you to post as you did , Marc. Holy Cow! Why would anyone want to argue the micro BS that went on over Cutting Tempered Glass... "Who Cares?" actually came to mind several times.

As far as I'm concerned, You've supplied good info. I agree with all of it....

[Ol'fogasaurus]

One thing to remember also it as glass ages it gets brittle. Also, not all states will allow Lexan front windows as I remember.

Lee

[Marc]

...not all states will allow Lexan front windows as I remember...

I'd imagine that's true - technically Lexan isn't approved by federal law, but local authorities seldom concern themselves with enforcing that...if you live in a state that requires periodic safety inspections you'd definitely want to find out what the local interpretation is before making a windshield from Lexan. The stuff is totally safe and will stay in fine using only the stock rubber seal if it's cut to the correct size and no less than 3/16" thick (if you're worried about it blowing in at speed you might want to add a metal bar in the center between the ceiling and dash; most racing organizations require the addition of external tabs to prevent it coming out, or require that it be secured by big-head rivets all around the perimeter) but it's susceptible to scratching from wiper blades and does not polish out well - best to avoid using the wipers unless absolutely necessary, just keep it Rain-X'ed.

Washington is mostly concerned with whether there's clear vision through the windshield (not cracked, overly tinted, or cloudy anywhere in the driver's line of vision) and whether the wipers and defroster are functional. I used to drive a Street Stock race car back & forth to work and got stopped a few times to make sure it was street-legal, and the subject never arose.