Cutting Glass

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roddguy

Well-known member
Joined
May 30, 2007
Messages
346
I posted this over at the killbillet sight and I figured everybody here would like to benefit from my vast knowledge to. lol.
No, I don't really take myself that seriously. :D

Ok guys, here is the real deal on cutting glass for chops.

I have a very good friend who owns an auto glass buisness. He is one of the best I have ever seen as he is the only guy our shop will let touch any of our jobs. This is how he does it.

You can't cut tempered glass..... period.
You can cut any type of laminate glass weather it be flat or curved.


You will need:

1) a high quality class cutting tool. There usually around 10 to 20 dollars. The type with the small cutting wheel on one end and the little hammer ball on the other. You should be able to order the good German made units from any automotive glass supplier.

2) Liguid lighter fluid that comes in the small cans.

3) Two pairs of plyers. Not Vise Grips.

4) Razor blades.

5) A helper ( not always nesassary )

6) GOOGLES !!!! Glass in you eyes aint funny at all. Trust me on this one.

This will be an example for cutting any curved laminated glass.

The obvious first thing you need is a template for the window opening. Some kind of light cardboard will be good for this. Once you are happy with the template you can lay it out on the glass you have choosen to use. in a custom situation you will need to consider the curve radious that you need to fill the opening and look good, but in most cases you will just need to cut down an original style window.

Always start with a new piece of glass. This may sound unbelievable, but glass gets brittle with age. So a new piece of glass is more plyable than an old piece and obviously easier to cut. Another interesting thing about glass is that it is actually concidered ot be a liquid and not a solid. Yes, this is true. If you look at glass in a tall skyscraper the window frames are made to expand at the bottom as the glass over many years will continue to flow to the bottom of the frame. Crazy huh!

So now that you have your template, lay it out on the glass. It is very important that you only make one cut at a time and never any intersecting cuts at the same time. It's best that you start with the hardest cut first. This is usually the cut on the top of the glass where it will curve down into the window the farthest. This is a simply because you don't want to waste your time on the easy cuts and crack it on the last cut.

Now take your new cutting tool with the small wheel end on the glass, and with firm pressure scribe a line along the pattern. Note, your not trying to cut right through, just scribe a good, well defined line. Always run your scribe lines right off the end of the glass so that when you break of the cut it will follow right off the glass and not crack in an odd direction.

Next, without flipping the glass, score a matching line on the other side of the glass. As you are doing this be carefull that you aren't putting any uneven pressure on the glass as this could cause it to crack.

Now flip the cutting tool around in your hand. Using the little ball hammer end, firmly tap along the scribe line, on the piece to be removed, booth top and bottom. You will be able to tell when they are fully severed when you can see that silvery mirror affect reaching down along the scribe lines to where the vinyle laminate is between the two layers of glass.

At this point take your lighter fluid and poor it along the scribed line and light it. ( CAUTION : never poor more lighter fluid on while it is still burning. The fire could climb back up into the can causing severe injury )

This will not hurt the glass, but rather, it warms up the vinyle layer between the two layers of glass. Make sure it is good a warm all along the cut. It is also possible to use a heat gun for this. With it warmed up you can now use the pliers to gently pull the cut piece away from the rest of the glass. This is where you may need help if the piece is to large to handle alone. You must do this gently and evenly, but just enough to fit your razor blade in the crack and cut the vinyle layer. Do not let the cut piece swing up or down as this may come in contact with the edge of the good piece and cause a crack.

In some cases in may be better to cut the ends of the glass panel first in order to make the longer cuts more managable.

So now just continue this procedure untill you have made all your cuts. If you don't have access to a professional type window sander the next best thing to do is water sand your edges with 320 or 400 grit to lighty soften all the edges and round the corners.

I would suggest that you practice this on some flat safety glass untill you feel comfortable before you attempt the real deal. You can buy it from your local glass supplier. Like the stuff they use for school buses. sometimes they may even have some pieces left over that they may give you to practice on.

I'm sure this may sound a little complicated, but it really isn't that hard to master and the results for very saticfiying. Hey if I can do it anyone can.

Here are a few pics of a job I did a couple yrs ago. Althought it's hard to tell from the pics the glass is actually curved both in the horizatal and vertical plain, and was cut from a new piece of side glass for I believe an 80's blazer. Because there are no staight lines on this cut it was actually a fairly hard piece to do, but was done using the method I just decribed. The moulding that was used when installed is actually a BMW reverse rubber type used on front and rear windows.

I hope this helps. If anyone has any further questions or needs some clarification on any points I'll be glad to help.
 

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I knew this was going to be the first question. ;)

The reason you don't want to flip the glass is that you will change the pressure on the glass and it will crack. Usually right in the centre, from top to bottom.

The way we do it is to have the window sitting on a metal sizzor stand that has the foam wrap on the work surfaces with the curve of the glass pointing up. It is much stronger in this position.
When scoring the back side ( which in this case is actually the front of the glass ) you simply look through the glass as you run the cutter under under it. Going slowly, it's not to hard to follow the scribe line on top. Use your free hand to put a bit of pressure on the side that is already cut and stay very close to the cutter. Note, your hand must always stay inboard of the cut line as well. Inboard meaning your hand is on the part of the glass that you want to keep. If you push down on the outside of the cut line, (pushing on the part to be removed) you will crack it on the side being cut.

One thing to remember guys is this isn't black majic, and it doesn't take a whole lot of pressure to make a good score in the glass. Like I said, just practice on some flat laminate first to build your confidence and before long you will be cutting like a pro.
 
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Excelent tech article. I understand completely and it makes good sense.
I will be doing this for sure.

I have a buddy that went through 8 front windshields for a 59 Impala he chopped. The way he ended up finally doing it was nibbling off tiny pieces, 100,s of them. It just didnt seem right to me.

Thanks a lot for this.:cool:
 
Your very welcome guys. This is something that I hear a lot of comments about. Seems lots of guys are a little leary when it comes to doing glass for chops. Kinda like I used to be with wiring........ ok still am. :D

Glad I could help.
Randy
 
Very good tech tip. I worked in a glass shop 150 years ago while going to school. Thats how its done. If I can do it anyone can.

Thanks for sharing your knowledge.
 
Hey guys, I've just been given a heads up, from another very experienced glass man here, on a very good point that I did not mention. As you are scoring the glass it's not a good idea to stop and start again. It's best to make one continous smooth pass for each cut.

Thanks Captian Moron.
 
Great tech post. There are a couple of things I remember from my days in the glass industry. We always lubed the cutting wheel with a bit of kerosene and made a half dozen light cuts on a piece of scrap to take the extreme sharpness off so it would cut with consistancy. New or "hot" cutters tend to chip the edges. We also liked to lube the cut line with kerosene on a brush. Just a little, to clean and lube the cut. Only other thing that we did different was, instead of lighter fluid, we used Coleman lantern fuel (basically alcohol). Seemed to burn just long enough to heat the laminate so you could slice with a new razor blade.
Just throwing this out there for what it's worth. Mike
 
Hey guys, I just reread this post and there is something that I missed in the original tech. If you need to make more that one cut on the glass you need to make each cut and removal of the cut piece separately. Meaning never doing more than one cut at a time and most importantly, you have to let the glass cool back down to room temp. before making another scibe line. That's just something I was recently reminded of.
 
I cant believe with this thread being so old, there hasnt been more discussion about it.
I am about ready to cut my curved windsheild of my international pickup chop top. I will need to take 7 inches out of it. I will certinly be using this artical to do my glass.
I have practiced on the old flat glass a few times and have ALMOST been successfull ;)

Im pretty worried about the windsheild since im having a hard time finding replacement glass already in stock form.

I definatly reccomend going to your local scrap yard and grabbing a couple chunks of glass to practice on. I will be grabbing a nice curved piece to try my hand on it before i try the final product.

THANKS for the artical!
 

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