Best way to stop a crack

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burnman
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Best way to stop a crack

Post by burnman » July 7th, 2006, 2:26 pm

Since I've only been in the business a few weeks I have not had much chance to practice this, but I've had problems stopping cracks. As I was trained, I drill about 1/16th past the end of the crack to the pvb and then try to run the crack into the hole. My problem is that a couple of times, the crack runs right past the hole and keeps going.

What is the best way to stop a crack? Should I use a larger bit?

Dependable Dave
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Re: Best way to stop a crack

Post by Dependable Dave » July 7th, 2006, 4:28 pm

Burnman, try drilling a little farther away from the end of the crack, up to an eighth or quarter inch. This is a tricky deal because the crack can take a quick left hand turn and miss the bullseye altogether. If the crack is pointy on the end, it may extend farther than you think because the little tiny narrow end of the crack is tight and just sort of disappears, even though it still continues on. If it's square on the end, that may be the true end of the crack.

Don't drill all the way down to the PVB. The function of your drill hole is to be deep enough to allow you to make a bullseye that extends from the surface all the way down to the PVB and will intercept the crack. If you drill too deep, there is no glass left to make a bullseye. Or you might say that there is a tiny bullseye way down there at the bottom that has no chance of intercepting the crack. The crack just runs over the top of the bullseye shoulder. The drill hole should not go more than half way thru the outer layer and should never touch the PVB because it can be damaged. Also, if you hit the PVB with the bit, you will burn it and leave black residue in the hole.

As for bit size, the smaller the better, when it comes to a nice look. The downside is that little tiny skinny drill bits are really fragile. You certainly don't want to break one off in the hole! Another problem with a drill hole is its tendency to trap an air bubble at the bottom, under the pit filler resin. Use a needle to drag that bubble out before you cure your pit filler.

Finally, the shape of the probe used to make the bullseye is important. A needle-sharp point will make a star. While this is useful in certain circumstances, what you really want for this operation is a blunt tip so you get a bullseye. My probe is blunt on one end and sharp on the other end and I just reverse it when necessary.

In the end, lots of practice will make you good at this. Mistakes or accidents will begin to diminish over time. And you will soon begin to appreciate the unpredictability of glass.

Best regards,
Dave Beyerlein
Master Trainer, NGA Certified
Dave's Windshield Repair
Cedar Park TX

sunshine wr
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Re: Best way to stop a crack

Post by sunshine wr » July 7th, 2006, 6:57 pm

Hey, Dependable Dave, good to see you on here; was asking the guys at the shop about you the other day; they said you moved to Texas. Hope things are going well there. See ya later. Yancey - Sunshine Windshield Repair.

P.S. I guess you do remember me?

Sorry burnman - didn't mean to change the subject...

toab
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Re: Best way to stop a crack

Post by toab » July 7th, 2006, 11:07 pm

I was useing sewing needles for mini bulls but I find that my probe and tappet works better than the #18 needles I think because the probe has a little weight to it.By the way D.Dave it sounds like you are a real veteran at this bizz.I'm kinda wondering if yuo could start an educational post on stabilizing cracks.I have heard some techs talk about running a crack until they get it to stabilize. Somethin about heat and making the crack blunt.

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Re: Best way to stop a crack

Post by screenman » July 7th, 2006, 11:44 pm

One of the things I will also add is practise more on practise screen. Each time you fail to carry out a quality repair on a customers screen you have lost a customer possible for life.
33,000 + screen repairs over 18 years and still learning.
Over

Dependable Dave
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Re: Best way to stop a crack

Post by Dependable Dave » July 7th, 2006, 11:47 pm

Yancy D! Good to hear from you. I'm too new on the forum so they won't let me send you a private msg. Contact me at stillagruntafterall@yahoo.com

Toab, I've never run a crack until it stabilized but it's an interesting idea. I may be a little too conservative to try something that audacious, though. I guess that's why I need to put a practice windshield back in my garage. My worry is, how far do I have to go until it "stabilizes"? With the "built-in" stresses from the manufacturing process, the crack could start spinning circles or go left or go right. I've seen a guy pretty well control a really short crack by "pulling" it with the probe in the direction he wanted it to go. It worked once for me and now I'm 50-50 in that department.

As far as an educational post, I'm brand new to this whole idea and am willing to share all I know, just as the others do, right here on the forum. My time is pretty limited but tonight I've been hammering the keyboard mightily because I had some spare time. What I've learned in 10 years of this repair stuff is, there's a whole lot more to learn. This seems like a pretty good place to pick up tips. I know I have. Does anybody know if GlassCentral.com is still up and running? I used to moderate a forum there for scratch repair but have been out of the loop. Hi Billy!

toab
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Re: Best way to stop a crack

Post by toab » July 8th, 2006, 8:21 pm

This stopping crack stuff is pretty tricky at best.Sometimes i will pop a bull at the end and it will blow right by and other times i cannot get the crack to move into the minibull at all and other times as soon as i pop the minibullthe crack will blow right past as soon as I tap it and then I have to do it again.I think that sometimes the crack is longer than I can visually percieve it to be and i don't know how to get around this hurdle.

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Re: Best way to stop a crack

Post by GlasWeldTech » July 9th, 2006, 5:46 am

Billy still has his forum at http://www.glasscentral.com

CV Windshield Repair
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Re: Best way to stop a crack

Post by CV Windshield Repair » July 11th, 2006, 8:31 am

If the crack is longer that it appears to be, when you attempt to tap a bullseye you will end up with a half bullseye. If you are going to try to pop a bullseye at the end of a crack it is very important that the windshield not be hot. A hot windshield is VERY sensitive and the least movement (as when trying to pop a bullseye) will cause the crack to move. If the windshield is still warm to the touch you need to move the spot where you drill out a little further, I usually take my ballpoint pen and mark where I plan to drill. This serves two purposes, one it helps you determine if you are far enough out from the point and two, it helps you to see if you are lined up with the point of the crack. The second is probably more important, after marking the spot with your pen you can go inside the car and see if it is lined up. The problem with just looking from the outside of the car to see if it is lined up is that sometimes it might appear to be lined up but is off a little. The ideal situation is to pop a bullseye and the point of the crack will run into the bullseye. However that does not happen all the time, sometimes when you pop your bullseye the crack stops short of the bullseye, if this happens use your thumb and gentley push from the inside about one inch away from the point. If the crack does not move apply a little more pressure, normally this will cause the point to meet the bullseye. That is why it is so important to make sure that you are lined up with the end of the point.

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Re: Best way to stop a crack

Post by Bois » July 13th, 2006, 5:30 pm

Boy!! All these good tips. Haven't seen so much good advice on this forum in a while. Thanks to everyone. :)

Dale...

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