I give. I tried searching using a combination of keywords like cut, cutting, gl***, windshield, how, etc but no luck. Surely its been covered before, but I'll ask anyway. I have a slightly curved rear window from a donor car I'd like to use for a windshield in my 28. What method are used to cut gl*** cleanly? I have heard of sand blasting but I don't understand how you focus it sharp enough to get a clean cut.
sand blast curved lam, no way to cut saftey that im aware of, and i worked in a high end gl*** shop for several years.
Rear windows are usually tempered and will shatter into a billion little pieces if you try to cut them. ALSO, just using one as a windshield is a BAD idea for the same reason. Picture a rock or something hitting it at 70mph and, boom, a billion little pieces of gl*** are flying at you, not so good.
If its from a donor car old enough than it will be laminated gl***. You could try a gl*** shop, sometimes they will be up to the challange of saw cutting, or regular style cutting it. Your risk of course. We tried a few at the gl*** shop I worked at for 5 years, and had about a 25% success rate. The less curve the better. The sandblasting method is prefered by most because you have less chance of breaking it. Draw a line where you want to cut it , and mask off the good side with thick rubber. (ive used roof rubber before). Ive glued it, taped it, and tried alot of ways to keep the sand from getting under the mask, but the key is to shoot the sand at an angle facing the part you are cutting off. Every p*** you make with the sand removes material from the gl***. Just take your time until it is all the way through. The edges can be claned up with a belt sander and a 220 grit belt. (be very gentle and dont let the gl*** heat up). Slow is the word to rember, you need alot of patience. I would suggest you go down to your local autogl*** shop and dig a busted windshield out of the dumpster and try on that a few times first. Good luck
I guess I really don't know what I'm talking about. What is the difference between safety gl*** and laminated? I didn't realize windshields were made of different gl*** than the rest of the car gl***es. This was a rear window out of a 71 Capri I had laying around. What do people use for flat front windshields? Can I just use a piece of Lexan? I understand its more durable than regular plexigl***. This is for my 28 RPU but I will be making custom windshield posts and mounting.
A back window is tempered, it will break into lots of tiny pieces. It is used in all modern car windows except the windshield, that is laminated. 2 layers of gl*** with a thin plastic in between. Rear windows have been tempered since at least 1947. Flat front windows are cut from laminated gl***, any good gl*** shop can help you out with that. Polycarbonate (Lexan) will scratch far easier that Acrylic (Plexigl***). Neither plastics are good for a windshield in a street car, have a gl*** shop cut a laminated gl*** one for you. You can make a template out of 1/4" masonite, or hard board.
Determine if it is laminated or tempered. MarkX has cut laminated with success using a sandblaster. I'm sure he could do it.
If you're going to use a plastic windsheild DON'T use Plexigl*** It will break into sharp shards and youwill get cut. When making windows out of plastic use LEXAN!!! It is alot stronger and won't break when hit by rocks, bats,bullets,etc.It's not bullet proof , but it wont break into shards.
Don't necessarily recommend this, but I trimmed my windshield gl*** after we chopped the coupe using a cutoff wheel. Masked my line, then used a light touch to score the gl*** with the cut-off. My wife helped by slowly pouring water over the cut to keep heat down. Once both sides were scored, I poured alcohol in the cut, lit it, and broke the gl*** away while the fire melted the plastic. Then I used a 100-grit (and a light touch) to clean up the edge.
Which you should be able to polish out.... the first set of lexan windshields I made for my Chevy did that when I got too close to the heat (kitchen stove) prior to pressing it over my form. a bit of sanding through the grits and onto the buffing wheel, then hand sanding to remove buffing marks removed the fog...
In Canada, plastic and lexan are not Department of Transport approved for windshields. You can not get a safety sticker to license the car if you do not have laminated safety gl*** in the windshield. It might be wise to check out your states legislation on windshields before you spend too much money on something that can not be certified.
Ohh,fire! I like fire!. Seriously, it sounds like you put a lot of thought and patience into it. I've heard something about gl*** shops using a burning string to cut laminated gl***,but I'm not sure quite how.
Laminated curved backgl*** was used on some of the older car (40@50's"), but check and make sure before cutting!!!! When I frist started cutting gl*** 30 years ago it took practise on many old windshields, learning what carve gl*** did when you cut it. SO practise frist!!! TECH, This is what I do in cutting windsheild and backgl***: 1. Make sure you support the out side of the gl*** 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 gl***). Always start by cutting the inside curve of the gl*** frist so that the pressure of the curved gl*** is relieved. I use Pure VM&P Naphtha for a lubeurcant 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 gl*** from THE CENTER OUT!!! Never from from one side to the other(I use gl*** pliers for breaking and tapping). 2. Reverse this same steps for the out side of the windshield. 3. Now you have to make relieved cuts at the curved area to the outside edge of the gl*** to be able to break off the excess gl*** not needed and not to flake the edge of the gl***. 4. Ok, for the Fire. I use a porpane torch for heating the gl***. Brush the break lines in the gl*** 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 gl*** cut. If you heat the area of your windshield, later on in years it will bleaster (like little air bubbles). After wraming the gl***, 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 gl*** 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 gl*** belt sander with 3"x24" 180 or 220 grit gl*** sanding belt. iT'S REALLY NOT THAT HARD, it just takes a little patients. Hope this will many of you in being able to cut gl*** for your rides. "S***ch"
tempered safety gl*** can not be cut by hand it shatters insistently, there is a way to cut regular saftey gl*** but I don't know how it is done.
you DON'T want that back gl*** in front of you, there's a lot of really good reasons they started putting in laminated safety gl***, people used to go blind from the old gl*** shattering in their face.
JFI, I'm rpetty sure safety-gl*** started to be offered about 1935. Petroleum-derived "plastics" were years away, so the closest thing available then as a laminant was Celluloid, made from wood fiber and coal extracts. This is why about EVERY '30s car you see that's sat outside for years has the middle gl*** layer severely yellowed and usually bubbled. Anyway, GOOD thread!
I worked in a gl*** shop in the 60's. Most older cars had laminated gl*** for the side windows as well as the windshield. They were all flat gl***, the curved side gl*** is all tempered as well as the back windows. We cut the side gl*** from a big sheet, they were all cut to size. Like a previous post, you cut both sides first and then cut the plastic with a razor blade. We never cut any winshield gl*** like that, they all came pre-cut and ready to install. I'm sure its a bit more complicated to cut a curved peice depending on how much curve. I would get a broken winshield from a gl*** shop and practice on it though. Probably get one for free, there is no s**** value.
Thank you S***ch !! Can we put this in the tech archives ? I am going to practice on some junk gl*** when I get home.. Dave
I did see it done on a show one time . It was flat gl*** ONLY ! They took a gl*** cutter and ran a line on both sides of the gl*** . Tap lightly on both lines then heat carefully with a small gas torch to melt the plastic . Now this is side windows . Now as for Tempered windshield I don't know . It can be done but you really need to know what you are doing . It will break very easily . Just take an old broken or cracked gl*** and try some different things to see what works . RetroJim
Very simple. Tempered gl*** shatters. DO NOT USE IT FOR A WINDSHIELD. Most gl*** shops will cut laminated/safety gl***. Make a pattern and take it to them for your flat pieces. If is a side door gl***, take the frame. They'll probably even put it in for you. The back gl*** you mentioned is TEMPERED. It WILL shatter.
The guy who cut the flat side windows for my car scored one side with a cutting tool, poured a little rubbing alcohol in the groove, lit it, let it burn itself out, then scored the other side and split it.
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