Laminated curved backglass was used on some of the older car (40@50's"), but check and make sure before cutting!!!! When I frist started cutting glass 30 years ago it took practise on many old windshields, learning what carve glass did when you cut it. SO practise frist!!! TECH, This is what I do in cutting curved windsheild and backglass: 1. Make sure you support the out side of the glass on a table with blankets (or???) to hold it frim while making you cut on the inside (you much think of it as being a flat piece of glass). Always start by cutting the inside curve of the glass frist so that the pressure of the curved glass is relieved. Start on one side of edge of you cut line on the glass and make one cut all the way to the other side with study pressure. I use Pure VM&P Naphtha for a lubebricant and brush it on the cut line. Dip your cutter in it also (always use a new cutter). After making your cut with the cutter (this is important), tap the out side of the glass from THE CENTER OUT!!! Never from from one side to the other(I use glass pliers for tapping and breaking). 2. Reverse this same steps for the out side of the windshield. when cutting the opposite side of the glass, make sure your cut is exactly on top of the other cut or it will chip in breaking the excess glass off. 3. Now you have to make relieved cuts at the curved area to the outside edge of the glass to be able to break off the excess glass not needed and not to flake the edge of the glass. 4. Ok, for the Fire. I use a porpane torch for heating the glass. Brush the break lines in the glass with Naphtha (you don't need much). Light it up and REMEMBER TO KEEP THE TIP OF THE TORCH too the out side of the glass cut. If you heat the area of your windshield, later on in years it will bleaster (like little air bubbles). After wraming the glass, carefully bend the cut-off down and use a razor blade to cut the plastic laminent. 5. For the last step: all sharpe edges of the glass much be seamed or beveled to make for an easy installation into the rubber in the car (also a sharp edge will break real easy in lipping it into the rubber). For this I use a hand glass belt sander with 3"x24" 180 or 220 grit glass sanding belt. iT'S REALLY NOT THAT HARD, it just takes a little patients and it's a lot of fun. Hope this will many of you in being able to cut glass for your rides. "Stitch" __________________ "Stitch" Last edited by Stitch : Today at 05:00 PM.
Since a lot of the backglass in popular 50-60's cars to chop is tempered and not laminated that procedure will not work. Be sure you know what you have. Notice that many chops either lay the back glass foreward, drop part of it into the trunk, or fab in something from another car. Tempered glass is the reason the original is not cut. Some have had luck cutting tempered with a sandblaster, Ive also heard of water being used under extreme pressure. However if you make a mistake you dont run down to the junkyard for a $10 replacement any longer. My 53 Vicky is staying unchopped until I find a real glass expert; I dont have the balls to try it myself.
Stitch, good job! I just would like to add a couple items not trying to confuse things. Laminated glass is two pieces of glass with a vinyl layer in the center. ALL WINDSHIELDS in the USA are made this way since it became law in 1939. Tempered glass (heat treated) is solid (one piece) all domestic passenger cars since the late 30's that are curved are made this way. there have been some wagons, busses and vans with laminated glass but are rare. I've heard stories about cutting but have never seen, nor believe that tempered has ever been cut. The good news is that alot of the new re-pop backglasses are laminated. ask when you order them. another option is to find a windshield that has the same (or similar) curve as the back glass and cut those. I've been doing nothing but autoglass since 1965 and haven't come close to making all the mistakes but I'm getting closer every day.
GreaseBalls. that's a cool nick name!!!!!!!! Tried to post this in the Tech Archives, But I got blocked from doing so.
NoName you are correct, very few BackGlasses where Laminated, so always check frist. I have never tried to cut tenpered glass. When you can, as GreaseBalls said, you can cut and lay the rear window openig down.
You can cut tempered glass....BUT... You HAVE to un-temper it first. This is a job to be done in a glass factory, or similar. Each manufacturer tempers it's glass at a different temperature. You have to know this to bring the tempered glass up to the correct temp to un-temper it. Then the glass has to be cooled down at a controlled rate, to be "soft" again. Actually, unstressed is a better word. Then you cut it, and have it re-tempered. So, Stitch, have you tried your technique with a very severe wrap around windsheild? 55-57 Chevy, perhaps? I tend to think it may be a crapshoot on one of these, due to the extra stress the curvature has on the glass. But I am not a glass guy and I haven't cut any curved glass that way. I have done plenty byu sandblasting, and have been very successful. I started when I chopped my 55 Olds, and NO ONE would touch cutting it! Had to learn and do it myself, and I've done MANY chops since then, and am pretty successful with cutting even severe wraps. I'd like to know an easier way, as my technique is very time consuming!
ChopOlds, I did not know once glass was tempered that it could be un-tempered, and can not see the it would be cost effective. I guess any thing can be done if you try hard enough. Yes, I have done many severe curved windshields through the years, and yes, more of a curved there is - the more chance of it breaking. Theirs been many times where sweat runs down my forhead and get very nervous, but it's a roll of the dice. As a small chop or even as a friend there are no garrantes that it will be a successful cut on any glass. That brings to mind a few months ago, of a windsheild I cut for CycleBilly from the VooDoo Kings on his Chopped Cadillac looking Chevy. He's girl friend Cazy asked, You do garrantee it not to break don't you, and I said, NO!!!, BUT FOR YOU I WILL. Well it was a successful cut. I don't know how many windshield I have cut for many chopped cars and trucks (and sweat still rolls down my forehead), but I have had a 100% success rate using this method. I think the key in cutting curved glass is taking time to support the glass properlly on the table before cutting // a good lubricant // a good new glass cutter // and breaking the cut line from the center of the windshield out to each side. Hope you have more fun cutting // instead of sandblasting!!!
The method of cutting tempered was passed along to me by a guy who does a lot of late model chops, mostly pick up trucks. The door and vent window glass is tempered, and curved, so making new ones, or substituting something else is not an option. Lots of things we do aren't cost effective, but to do them right really shows in the outcome! the other option is to have custom glass made, that is even more expensive. The rear window on Jerry Kinds-built Barris Kustom, the Chrysler City Coupe, cost about $10,000. But a second glass made at the same time was only 6000. I'm not sure how much the guy from Finland(?) gets to make a custom windsheild, but I am sure it is similar in cost. John D'Agostino has them made regularly for his customs.
I think this thread got off on a tangent. I have a guy in Portland that bends glass but I have problems having curved glass tempered. anealing (untempering) glass doesn't help cutting extreme bends, and retempering is still a problem (for me) anything can be done for a price, but producing the first is the problem. sometimes you can manufacture 100 at the same price as one (but who wants 100 identical customs) yesterday I cut a GM truck windshield down to a custom carson topped car. used a 66 inch wide truck windshied (because it had the right curve) to make a 10X19 inch backglass! cost $100.00 plus the windshield. I don't have a set price I charge by the amount of sweat produced by the job haha
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