My crater!

[GLASSTIME]

Yesterday,

I went into a practice stage!
I wanted to fill some time and what better way to do so than to pull out the stand and the P. Glass!

I first popped me a Bullseye and then struck the center of the Bull's with a nasty star. Here latley I've been really interested in perfecting my Nasty of Nastiest Breaks!

And let me say it was Nasty!
I first of course cleaned it out. Filled with Pit and cured.
Then I drilled what I was sure was the impact point, However I discovered it wasn't so then I just drilled straight into the bullseye itself.
When i started to drill after about 3 or 4 seconds the bit dropped down hard, I thought I damaged the laminate. But nothing appeared as if it was destroyed.

I filled and it turned out perfect!

Wondering why that drill dropped down so hard. Was it that I passed all the cured resin and hit the glass?
Or was it that i did indeed hit the laminate?
If hitting the laminate so hard with the tip of the bit, Wouldn't that have damaged the laminate?

[Spike]

Firstly, I'm no EXPERT

But as I understand it, you never drill a bullseye at the impact point.
To understand a bullseye, you need to find an image of a Cross section, then you will see if you drill the impact point, you are in fact drilling into an area of unbroken glass.
If you do need to drill a Bullseye, you should indeed drill near the outer edge as you did, as this will lead down to the lower area of damage.
The sudden drop you felt on your drill is the drill going through the glass and into a void. IMHO

Spike

[adam@gtglass]

Firstly, I'm no EXPERT

But as I understand it, you never drill a bullseye at the impact point.
To understand a bullseye, you need to find an image of a Cross section, then you will see if you drill the impact point, you are in fact drilling into an area of unbroken glass.
If you do need to drill a Bullseye, you should indeed drill near the outer edge as you did, as this will lead down to the lower area of damage.
The sudden drop you felt on your drill is the drill going through the glass and into a void. IMHO

Spike

Reviewing his post, I think he was talking about a practice break he created which was more complex than a simple bullseye; from his post, it looks like he made a bullseye, and then punched a star break in the same location as the bullseye, complicating the break into a combo. This would leave a much more fragmented impact point that might have made drilling necessary in his case.

[GLASSTIME]

Adam,

Your right. This was indeed a piece of practice glass. Yes I filled the crater as usual as if I was out in the field. I then drilled to the outer edge of the break into the bullseye.

I was only wondering what the sudden frop was. But I figured that part out already as I simulated this 2 extra times.

Thanks!

[Brent Deines]

Just a guess but it sounds to me like you went all the way through the first layer of glass and into the lam. When filled properly the drill hole may be a bit more visible than if you only drilled part way through the outer glass, but it will still look good and in some cases you may not be able to tell that the drill hole is all the way to the lam.

When you go through the first layer of glass the drill typically slows a bit just before breaking through, then speeds up just as when you drill through a board. The sudden frop was probably when the bur broke free of the first layer of glass, sped through the lam, and touched the second layer of glass. Again, this would be like drilling through two boards with an air space in between. You hear it and feel it at the same time.

It would be very unusual for me to drill such a break, but with that severe of damage it probably would not take long at all to go through the first layer of glass. How deep was the bur embedded in the glass when you stopped drilling? This should tell you if you went through or not.

[GLASSTIME]

Brent,

Keep in mind I had to fill the large void before beginning as the void was entirely to large as it was larger than the seal.
I drilled due to filling the void and curing. Leaving the original impact point to be filled and cured as well.

I would say that the bur was maybe 1- 2 cm deep.

[screenman]

Did you drill into an area of compacted broken glass, for example the middle of the star that you made?

[Brent Deines]

Brent,

Keep in mind I had to fill the large void before beginning as the void was entirely to large as it was larger than the seal.
I drilled due to filling the void and curing. Leaving the original impact point to be filled and cured as well.

I would say that the bur was maybe 1- 2 cm deep.

Sorry, I forgot that part. In that case there are a couple of things that could have happened. The "frop" you mentioned still sounds like you went through the first layer of glass to me, but it could also be that you went through the cap and into an air pocket below the cap, then hit the outer layer of glass. Unless the damage in the pit area was all the way to the lam to begin with you would still hit the hard glass as the bur penetrated through the resin cap. In this case the drilling would have been very easy and fast, but the drill speed may still have sped up a bit as it entered the air space and and the frop sound/feel may have come when you finally hit the glass.

I assume you mean 1mm - 2mm as 1cm would be all the way through both layers of glass. 1mm would not be through the first layer of glass. 2mm could be very close to being all the way through the glass, but usually the outer layer of glass is just slightly thicker than that. Normally if you drill completely through the first layer of glass you also drill through the lam because it happens so fast, in which case you would likely be around 3mm deep to the bottom of your drill hole. Not all glass is the same thickness so there is a bit of a variance here, but you can use that for a general rule of thumb.

In this case it sounds to me like you did not have the typical cone in the center of the bullseye due to the extent of the damage you created in the center of the break by adding the star. My guess is that either there was a deep void in the center where the cone would normally be on a bullseye, or if you did not remove it, there was some crushed glass in that area. Either way there would be little resistance to drilling until you hit a hard surface, and it is possible that the first hard surface was the 2nd layer of glass, but again, 2mm deep does not indicate that to be the case.

There is a great deal of speculation in my theory so I could be way off base. I just figure if we throw out a few options and give valid reasons for our theories something may click and you will know what caused the frop. I may be putting the cart before the horse however, so by all means answer screenman's question and see if someone comes up with a more logical theory.

Try this. Drill completely through the first layer of glass on a practice piece of glass. Do you get the same frop?