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Cutting C/K Glass after Chop

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  • Cutting C/K Glass after Chop

    Does anybody have any copies of articles or ideas that describe cutting front and back glass for a C or K after a chop? Seems like this has been covered, and one of our customers was asking about this.
    Thanks
    Special Interest Autos, Motos and Restorations.

    Ben

    bekglm1@aol.com
    SIAR/ Special Interest Autos, Motos and Restorations
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  • #2
    Im sure it can be done but every one I have ever seen was either chopped in such a manner as to allow the original window to work or the sides of the rear were filled so that a flat glass would fit (which looks terrible IMHO).Steve
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    • #3
      About the only way I have heard to cut curved glass is by sandblasting through it. Mask, and hours of blasting through it with an industrial sized sand blaster.
      Here are a few links to articles

      http://www.jalopyjournal.com/forum/s...d.php?t=296834

      http://www.jalopyjournal.com/forum/s...d.php?t=207219

      54 Champion coupe
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      54 Champion coupe
      48 Champion Convert

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      • #4
        Theres, a couple widely used methods.

        Tape off area to be cut, and use belt sander, with luke warm water on hand to keep heat in control. (long long way to do it)

        You can scribe tempered glass(then use glass knippers till the curves and take it a small bit at a time through the curve.

        Sandblasting can be done, but great care in protecting the glass you want to see through will need to be carried out, plus, the blasting will take quite some time, and blasting media, unless you have a big booth. But you still have the heat build up to keep an eye on. Then a belt sander/grinder will be needed to smooth edges.

        Safety glass, heating up the glass to seperate the two plates of glass and cut/scribe in same manner with nippers. And grind to a smooth finish.

        There will need to be modification to the window surround to fit the new glass, and a decision needs to be made....Will the new glass be flush mounted, burried, or as close to stock as possible. Each has its pro's n con's, and all take time.


        Not having studied a C/K it has a nice roof line as it is, a minor chop in the front of say 1 to 1 1/2 inch with pie cuts to the rear pillers would leave the back glass pretty close to stock with minor work for it to fit,

        How much are they planning (or already have? )on chopping the C/K?
        ChopStu
        61 Lark

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        • #5
          You CAN NOT CUT TEMPERED GLASS!!!!!No matter how many half baked methods people come up with, it will only leave you with a pile of broken shards!!! When tempered glass pieces are made, they are cut to shape and formed to the required curvature. Then they are heated in a tempering oven and have jets of cooling air directed over their surfaces. This leaves the glass much stronger than standard float glass. But once the surface tension is broken (by a sufficient scratch or blow), the whole piece will disintigrate into small chunks. The only way to modify a piece of tempered glass would be by annealing it first, modifying the shape, then re-tempering it. The side glass on older cars and the windshields on all cars since the early '30's are made of laminated glass, two layers of glass with a layer of vinyl fused between them. Although a windshield can be cut down by scoreing it with a glass cutter and snapping it along the line, it's a risky process. And the older the glass is, the more difficult is seems to be. The most consistantly successful process is to lay out your cut line, mask around the line heavily with duct tape and work along the line with a fine sandblasting nozzle and fine grit. Blast part way through on one side, flip it over, do the opposite side and finish up with the first side. Once both sides are blasted through, cut the remaining vinyl with a single edged razor blade. Work carefully and don't heat the glass up while you are sand blasting or you'll cause a runner. And odds are, the runner won't go into the waste side of the cut.


          R2Andy
          R2Andrea

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          • #6
            There might be help here with a phone call...

            http://machinedesign.com/article/flat-out-0221

            Brad

            http://www.tperformance.com/street_r..._to_chop_tops/

            http://www.pbase.com/image/65477668

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            • #7
              One of the weirder ways I have seen windshield glass cut it to draw your line on and scribe with a regular glass cutter on both sides...
              Then put lighter fluid on the cut lines and light it.
              The heat will cause a crack that (hopefully) will follow the scribe scratches...
              As far as the back glass?
              Best to search out the info posted here and elsewhere...
              Jeff[8D]



              quote:Originally posted by R2Andy

              You CAN NOT CUT TEMPERED GLASS!!!!!No matter how many half baked methods people come up with, it will only leave you with a pile of broken shards!!! When tempered glass pieces are made, they are cut to shape and formed to the required curvature. Then they are heated in a tempering oven and have jets of cooling air directed over their surfaces. This leaves the glass much stronger than standard float glass. But once the surface tension is broken (by a sufficient scratch or blow), the whole piece will disintigrate into small chunks. The only way to modify a piece of tempered glass would be by annealing it first, modifying the shape, then re-tempering it. The side glass on older cars and the windshields on all cars since the early '30's are made of laminated glass, two layers of glass with a layer of vinyl fused between them. Although a windshield can be cut down by scoreing it with a glass cutter and snapping it along the line, it's a risky process. And the older the glass is, the more difficult is seems to be. The most consistantly successful process is to lay out your cut line, mask around the line heavily with duct tape and work along the line with a fine sandblasting nozzle and fine grit. Blast part way through on one side, flip it over, do the opposite side and finish up with the first side. Once both sides are blasted through, cut the remaining vinyl with a single edged razor blade. Work carefully and don't heat the glass up while you are sand blasting or you'll cause a runner. And odds are, the runner won't go into the waste side of the cut.


              R2Andy
              HTIH (Hope The Info Helps)

              Jeff


              Get your facts first, and then you can distort them as much as you please. Mark Twain



              Note: SDC# 070190 (and earlier...)

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              • #8
                Jeff, that is basically how you cut laminated glass. Score each side with the glass cutter, get it to "run" along that line, and then pour a trail of alcohol along the line and light it. The alcohol flame will warm and soften the vinyl inner layer, allowing you to bend the cut open and slice through it with a single edge razor blade. When you've got your cutting done, dress the edges with a wet belt sander (not something you're likely to have unless you have a glass shop)or a hand held belt sander. Just don't overheat the glass while you're finishing it. You'll probably cause a runner that will ruin all your hard work. Using alcohol rather than lighter fluid works better because it dosen't smoke, stink, and cleans up easily with glass cleaner. It also burns cooler.

                R2Andy
                R2Andrea

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                • #9
                  Ben

                  First- a word of caution. Scoring the glass requires a sharp cutter and only score once. If you use a dull cutter the notch will not be deep enough to initiate the crack. Going back with a dull cutter will result in many small fractures that will result in difficulty controlling the cracking.

                  Secondly- The lighter fluid/alcohol/kerosene scenerio is chancy but does work. Any imperfection can cause the crack to be diverted in a non-controlled direction.

                  Lastly- It is not a vinyl film but Polybutylene.

                  If I only had one piece of glass, I'd use the sandblaster.

                  Bob

                  PS- I'd probably cut the glass before the chop and fine tune the top to the glass. I also agree with the comment to not cut the rear glass but do the chop with the rear opening intact. If you do the whole top then slant the complete opening or turn it over like Dick's Ute.



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                  • #10
                    The material is polyvinyl butyral (PVB) to be technically correct. I've called it vinyl because most people wouldn't know or care to be that precise. If you want to try cutting down your own W/S, pick up a few junk ones from an auto glass shop. Practice on these with the sand blasting method, it's your best bet for success with your good W/S. As for cutting glass with a cutter, yes, use a sharp one. And dip the cutting tip in a bit of light machine oil before hand. This always makes for a better score. The cutters I use have replacable heads and brass handles with a built in oil reservoir. When you push down to make your score, they continuously lubricate the wheel. Great if you use them all the time but pretty pricy for the occasional user. Heating the glass with alcohol (or whatever) is only to soften the vinyl, not cause the score to run.

                    R2Andy
                    R2Andrea

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                    • #11
                      You cannot cut tempered backglasses! That's why '50 Mercury lead sleds got so swoopy. The backglass could not be cut down in height, necessitating laying it down at a steeper angle.
                      But there may be a bit of good news for us Stude fans. I BELIEVE the 53-61 C/K bacglasses that are being reproduced are laminated...that means they CAN be cut down. But the serious problem remains: maintaining the matching corresponding opening in the car. You are dealing with a compound curved opening. Taking a section out of the middle height of the opening--you don't take the middle section out of the glass.[B)][8] Takes a true craftsman with much experience in top-chopping to get the two shapes to fit together. The "Projects" on eBay and elsewhere that have already been chopped, but are without glass--there's usually a reason they only got that far. Poor planning. No foresight. No glass is gonna fit.[}][}][}] BUYER BEWARE!!

                      KURTRUK
                      (read it backwards)


                      KURTRUK
                      (read it backwards)




                      Nothing is politically right which is morally wrong. -A. Lincoln

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