A question about glass

[Mike OMelia]

I need to drill some holes in safety glass. What kind of bits do I use and where do I get them? And what techniques are involved?

Thanks !

Mike

[Van Huskey]

I need to drill some holes in safety glass. What kind of bits do I use and where do I get them? And what techniques are involved?

Thanks !

Mike


What size holes are we talking about. I assume by safety you mean tempered? What thickness of glass?

[Andrew Nemeth]

By "need" do you mean "want"? The reason I ask is becuase it is my understanding that the only way you can drill tempered glass is to anneal it in a kiln then drill it and then re-temper if needed. This is assuming it is not laminated with layers of plastic, if it is I am not aware of anyway to do it. I have never seen a case were it was less expensive than just reordering a new piece of tempered glass with the holes drilled before tempering.

[Will Overton]

I know nothing about drilling glass, but just received an email from Dremel about a new glass drilling bit.

http://www.dremel.com/en-us/AttachmentsAndAccessories/Pages/AttachmentsDetail.aspx?pid=662DR

[Van Huskey]

my understanding that the only way you can drill tempered glass is to anneal it in a kiln then drill it and then re-temper if needed. This is assuming it is not laminated with layers of plastic, if it is I am not aware of anyway to do it. I have never seen a case were it was less expensive than just reordering a new piece of tempered glass with the holes drilled before tempering.


First forget the kiln, my wife who works glass for a living that quickly points out that is a recipe for disaster. 'Course then she went on to say you can't drill tempered glass, I calmly pointed out one of the tanks used in filtration for our 500 gallon reef tank is tempered and it has so many holes in the sides it looks like swiss cheese. Again I need to know the size of the holes and the thickness of the glass before I can comment. In my life I have drilled about 500 holes in tempered glass and had one shatter, probably because the glass has some score marks on it.

The key is the amount of temper in the glass which will likely not be something that you know. This can vary the success rate from 90+ percent to under 10%.

Andrew may have the best idea in ordering replacement glass. If it doesn't need to be tempered you could get it cheap wth holes or drill your own if you need a lot of them.

[Mike OMelia]

I think the correct term is shatterproof glass. It is the outer glass of an oven door. There are three other layers of tempered glass behind it, it's simply decorative but shatter proof. 1/8" thick. Holes no more than 1/4 - 3/8" for handle bolts. It just shattered. All tempered glass is fine. To replace, you have to buy the whole front shell of the door, metal and shatterproof glass for $250 delivered. There is a decorative polka dot pattern, no biggie, replace with smoked glass if possible.

So is it possible?

[Van Huskey]

My short answer on that is NO. Too thin, stress around the holes will be high etc etc. Just a very bad situation to even try it.

You need tempered glass for that application (for safety) and all the odds are against you drilling it.

However, check with a glass supplier and see what they can get for you, but my bet is at the end of the day you just get the part.

[Mike OMelia]

What is (was) in there is shatterproof glass, not tempered. When it broke, it shattered into thousands of itty bitty pieces. There were oversized bolt holes drilled in it to presumable prevent torqueing stresses from breaking it. Somehow, those holes were drilled, either by scoring or drilling.

[Dick Strauss]

Mike,
Tempered glass will act exactly as you describe...it is likely the holes were drilled before tempering.

[Van Huskey]

What is (was) in there is shatterproof glass, not tempered. When it broke, it shattered into thousands of itty bitty pieces. There were oversized bolt holes drilled in it to presumable prevent torqueing stresses from breaking it. Somehow, those holes were drilled, either by scoring or drilling.


If it broke into thousands of tiny pieces it was indeed tempered, shatterproof/resistent glass usually means it is laminated tempered glass. The holes in production tempered glas are normally placed before the glass is tempered.

[Joe Chritz]

That is tempered glass. It obviously wasn't shatter proof or it wouldn't have shattered.

Tempered breaks apart into corn kernel size pieces when it breaks to keep large chunks from falling and slicing you to pieces.

Same stuff they use in automobile glass, except the windshield which is laminated safety glass. It still breaks it just doesn't come apart when it does.

I would start at a glass supply and see if they can get the part you need. What about no holes and attaching some kind of handle with the stuff they hold on mirrors with on auto windshields?

I wonder what the heat would do to that?

Joe

[Ted Calver]

Check with the manufacturer. We had an oven door shatter and the manufacturer replaced it at no cost.

[Mike OMelia]

I punted and bought the part. Local glass company could do it eventually, but it would not be a whole lot cheaper.

Here is the rub. The engineers who designed this part did an awful job. Yes, the holes were oversized to prevent the bolts from torqueing the glass. But the the door panel can still flex and for the life of me I cannot see why they just did not make the window smaller with a couple of soft clamps around the edge to hold it in place. Its decorative anyways. If it ever failed, it should have been cheap (and easy) to replace.

I'd tell you the name of the brand, but that would probably be against the rules. Its expensive and its crap. Thanks, I learned a lot here.

Mike

[Ted Baca]

I have always been told that glass is drilled then tempered. Once tempered it can't be drilled or cut.

[Aaron Wingert]

Tempering creates a good amount of internal stresses in the glass, hence the reason it cannot be drilled or cut with any reasonable degree of success. Non-tempered glass doesn't have internal stress. For this reason, glass companies cut, drill holes and shape/polish edges prior to tempering. For the same reason, the glass is incredibly strong and able to resist impact of body parts and blunt objects.

Minor modifications can be made to glass after tempering if care is taken (grinding edges down a little bit, etc.), but even the pros will break it a lot of the time. Such things are usually done with abrasive means and not with cutting tools, and I think a hole would be out of the question.