Cutting a 125mm hole in glass window?

[GraemeCook]

Been thinking about your hole, Gibbo. I used perspex for a vent hole in my laundry - easy - but would look crappy if it was not hidden under a deck.

Will the usual 3mm window glass be strong enough to put a vent through - what are the council rules?

One option might be for you to have a go and if it works, thats great. If you stuff up then perhaps you can get a glazier to do it in 5mm glass.

Cheers

Graeme

[John99]

One way Ive put holes in glass is if you know someone with a abasive blasting cabinet pull the window out tape up all the area of the window that you dont want the hole in and blast it where you want the hole !
Its easy to put holes or even shapes in glass

cheers

[Wombat2]

Silent C is practically right in the method. Back when I was doing stainglass as a hobby I bought a circle cutter and successfully cut 2 circles first go (100% success rate ) all I ever needed to do. It is only necessary to scribe one side and tap around the scribe mark from underneath with the little ball on the end of the glass cutter. Glass is actually a liquid and the scribing breaks the surface tension on one side and you use the tension in the other surface to keep the fracture on line. You literaly are "parting the waters" from the scribed line down through the body of the material until you reach the other surface then break the surface tension on that surface at the last minute. The only time you need to scribe both surfaces is in laminated glass then "partially" break from both sides then use metho to dissolve the plastic layer in between.

[silentC]

Where you cutting circles or holes? There's a difference

The reason we scribed from both sides when cutting holes was that through trial and error we found there was less failure if we did that. It may not have been necessary but it's worth the effort when you are talking about a $40 sheet of glass that will be totally worthless if it fails.

It's difficult to explain why I think it makes a difference but next time you cut some glass, if you have a look at the edge, it is rarely a perfect 90 degrees. When you scribe and then tap, the fracture runs through to the other side on a random path. Usually it is straight down, but a lot of the time, it can run at an angle. When you are dealing with a circle, if the fracture doesn't run straight, it can run off the line a bit. Then when you tap adjacent to it, the next fracture will run to connect with the former one. This can create a deviation in the line outwards from the circle or inwards towards it. If the deviation is outwards, then a minute hairline crack can form in the bit you want to keep where the two fracture lines meet. When you come to trying to remove the waste from within the hole, if you put any stress on the outside of the circle, the hairline crack opens up and there goes your sheet of glass. The idea of scribing and tapping from both sides was an attempt to give the fractures a path of least resistance to follow, hopefully leading to less of these deviations from the line. It's possible it may have done nothing but statistically it appeared to be worth the effort.