Crack repair multiple failure

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MattAlaska
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Crack repair multiple failure

Post by MattAlaska » December 4th, 2021, 1:11 pm

I have a crack that I have tried to repair but the crack keeps extending beyond the drill point - it happens between the drilling process and the bullseye process.

I was using a pin and wood block to make my bullseye originally - I just received my spring hammer from DK and unfortunately this time also wasn't a winner.

I am wondering if my use of a diamond burr is an issue. I used a bit just > 0.047 that DK recommended for the spring hammer. Maybe it overheats the glass? I just placed an order for Tapered Carbide Burs .047 from DK just to remove this variable.

Any ideas? The tiny crack beyond the bullseye extended when I pressured the injector. Maybe I went too far on pressure or maybe this crack is my nemesis. I'm hoping this last repair will hold.

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Brent Deines
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Re: Crack repair multiple failure

Post by Brent Deines » December 10th, 2021, 1:13 pm

Sorry, missed this somehow. You've probably already talked with one of my co-workers about this but for the sake of other forum readers I'll give you my 2 cents.

We have found that the size and shape of the drill bit, along with the size, shape, and sharpness of the point on the tool being used are all very important, which is why we recommend the .047 tapered drill bit/bur if you are also using either our spring hammer or slide hammer.

The depth of the hole is also very important. Drill too deep and the point of the tool may go into the laminate, or worse yet into the second layer of glass. This can result in either no bullseye at all, or damage to the second layer of glass. Drill too shallow and you will likely end up with the problem you have been describing, the crack running past the drill hole. Use the depth tool on the end of the spring hammer to gauge the perfect hole depth when using that tool.

When using the .047 tapered bur it is important to rotate the drill slightly as the hole is being drilled to create the perfect shape for either the spring hammer or slide hammer, and it helps keep the bur from breaking off in the hole.

Be sure you are starting the drill hole about 1/32" past the end of the crack and that the crack pointing to the center of the drill hole. As you drill the crack should "jump" into the drill hole.

Use a sharp bur and light pressure to keep the crack from running past the hole while you are drilling.

Are you injecting resin from the impact point or from the drill point? I rarely recommend injecting at the drill point on a long crack as the pressure from the injector against the glass, or the resin being injected into the glass can cause the crack to run.

I've not had much luck with diamond bits overall, but doubt it is the heat that is causing the problem. I know others have had success with a wood block and a pin or needle, but in my opinion a pin is too thin and too sharp to get consistent results.
If the problem has persisted using a Delta Kits spring hammer or slide hammer, the issue is likely the shape or depth of the hole in my opinion.

I think if you use the depth gauge on the spring hammer, use a sharp .047 tapered drill, and use the drilling technique we recommend, you'll find you can get consistent results nearly every time and will not have a problem with cracks running past the mini-bullseye. However, we have had a few cracks over the years that seem to run every time you touch the glass. Toyota Prius windshields seem to be the most notorious for this! Repair enough cracks and you will experience that at some point, which can be a real confidence buster. When that has happened to me I've gone back to my practice glass and practiced my technique until my confidence is restored.
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kennycrane
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Re: Crack repair multiple failure

Post by kennycrane » December 17th, 2021, 8:07 am

Something that I have experienced before with a crack that you cannot seem to stop, is to make sure that the crack is on the outside layer of glass. If it is on the inside layer, it will always keep jumping past your drill point.
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