Windshield Repair Forum

I'm hoping that someone could help me figure what is happening here. I have been doing windshields about a year and a half now. I have drilled the end of cracks before in the past without problems. For some reason the last three crack repairs I have completed have given me problems. Before I am able to finish drilling and pop a mini bulleye at the end of the crack it extends past my drilling point. The vehicles were in the shade, temp of glass was suitable, new drill bit. This has made me very cautions on wanting to do cracks at all. With all the knowlegdable techs with years of exprieance on this forum I'm hoping that ya'll can throw some pointers out that can help me correct this problem. Thanks.

FNC is one of the few shops in AZ that will perform crack repair "full glass state" - and we capitalize on it !
*we find its the type of glass "O.E.M" or high end glass "pilkington,lof,ppg,lamisafe,mofo,carlite,safeguard,sekurit,+++ we never have problems with !
*If the windshield has been replaced before the glass could be under pressure - due to the installer not performing a deep enough cut out on the existing windshield therfore the new one is set at high and low points- causing flex/pressure
*AFTERMARKET glass=Safelite, xyg, criminex, xy, +++ "its only our opinion" cracks alot easier than O.E.M.
* Due you drill right on the tip of the crack ? or due you drill 1/8 infront of the tip of the crack ? We train all our Techs. on anything aftermarket or that looks like its been replaced before lead the crack an 1/8th and when you pop the bullseye it runs to it and stops ! also if you have a second person with you place them inside the vehicle with a wine corck it works great for filling in the crack were the pressure of the kit cant reach one of you take the resin bottle on the out side the other on the inside line the tip of the resin bottle with the cork press the cork slightly against the crack and follow each other up and down the crack it works better than anything/tool out there if theres two of ya it makes it possible to repair 20+inch cracks with no drlling other than the impact and tip !! Delta makes great thin resin for cracks "resin is also key to crack repair" if it flows in easier -its less pressure on the crack!!
* In crack repairing you should allways let the customer know there is a chance it will run during the repair process and you should have a solid invoice with a solid disclaimer/warranty - it should be signed before you start the repair !!! our company motto is = "WE'RE NOT MAGICIANS. WE'RE TECHNICIANS" I KNOW I RAMBLED A BIT BUT I HOPE THIS HELPS FNC

Have you changed the brand or style of drill bit causing you too use more pressure than normal?

Are you sure you are finding the true end of the crack? Sometimes, especially in hot weather the cracks will close up at the end. At times there may be several inches that you cannot see unless you flex the glass slightly from the inside, so I always do this prior to starting a long crack repair. I then mark the end of the crack on the inside of the glass with a sharpie before returning to the outside and proceeding with the drilling process. I drill about 1mm past my mark, directly in line with the crack, drilling about 1.5mm deep with an FG701 bur. I like the FG701 because it drills fast and clean, and creates just the right sized hole to use the slide hammer, which I use to create my mini bullseye.

Burning the melted glass dust off the bur after each repair extends the life of the bur and assures a good fast cut every time, but when a bur begins to dull requiring more pressure I toss it and use a new one.

I've had a few cracks begin to run on me when I started to drill, but not many using this process. However I find technicians miscalculate the true end of the crack and begin drilling at the wrong spot, so using an inspection light and looking at the crack from every possible direction from the inside and the outside of the vehicle is critical. Carefully using a bit of thumb pressure from the inside has also saved my bacon on many ocassions.

It happens to all of us! When this happens, take a second for a deep breath and maintain a clear head and focus. My process is find the true tip of the crack, drill about an 1/8th inch past the tip using MINIMAL pressure letting the bit do the work. When cracks continue to move I will drill further away knowing the the vibration of the bit will cause the crack to grow. Tap a bull using MINIMAL pressure, just enough to reach the stopping point. Sounds like your attention to temp and new bit is right on, you just got some tough ones.
For retail work, I ALWAYS sell drilling and popping to stop the crack as the hardest part of the process as some cracks are more "touchy".

yeauxusmc;31913 wrote:I'm hoping that someone could help me figure what is happening here. I have been doing windshields about a year and a half now. I have drilled the end of cracks before in the past without problems. For some reason the last three crack repairs I have completed have given me problems. Before I am able to finish drilling and pop a mini bulleye at the end of the crack it extends past my drilling point. The vehicles were in the shade, temp of glass was suitable, new drill bit. This has made me very cautions on wanting to do cracks at all. With all the knowlegdable techs with years of exprieance on this forum I'm hoping that ya'll can throw some pointers out that can help me correct this problem. Thanks.

I don't have this problem because I haven't drilled the end of a crack for at least ten or more years. Try it, you might like it. Saves a lot of time and frustration.

I ise an FG2 or FG701 with a sewing needle to pop and no problems with either size. If you do NOT drill deep enough it will advance the crack. Always get about 1/8 inch from the true end of crack works for me.

Thanks for all the input. I Might try switching drill bit. I find that the bits that I'm using don't drill that well even with a new bit requiring more pressure. I think this is where my problem is.