Tempered Glass Screen Protector - Cuttable?

Thread Starter

AlbertHall

Joined Jun 4, 2014
10,230
I am making a gadget which needs a window in its box. I thought of self-edhesive plastic film but I think this would be a bit thin. Then I thought of a mobile phone screen protector. Many of these are tempered glass which sounds ideal but can theey be cut to size neatly? I have a vision of brokrn glass if I try this.

Has anyone tried this?
 

jpanhalt

Joined Jan 18, 2008
10,080
My understanding of tempered plate glass (as used in modern cars) is that it must be cut wet using abrasive cutting. That is, the common method of a scratch and snapping as used for ordinary window glass will not work. I have no experience with it, though. That comment is based on what I have read and a friend's experience with the windshield for a highly modified antique pickup truck.

If you don't require tempered glass, double pane window glass may work.
 

oz93666

Joined Sep 7, 2010
737
If this window is fairly small , then ordinary glass will be fine , thicker the better (5mm) , your local glass shop will probably give you an off cut free you can cut to size ... this will be almost impossible to break once secured in your box ...mobile phones couldn't use ordinary glass because it's too thick and heavy ...

Tempered glass is the type that shatters into small gravel sized pieces , often used in cars ... this will always shatter if you attempt to cut it . Laminated glass is also used in cars ( and probably phones) , a sandwich of glass / plastic film / glass , this also cannot be cut .

perspex (acrylic) is another option , small off cuts cheap on eBay
 

jpanhalt

Joined Jan 18, 2008
10,080
Polycarbonate plastic is a bit more scratch resistant compared to acrylic and only slightly more difficult to work with. Ordinary woodworking tools can be used carefully.
 

shortbus

Joined Sep 30, 2009
7,841
My understanding of tempered plate glass (as used in modern cars) is that it must be cut wet using abrasive cutting.
I've never heard of that working on tempered glass in cars, the side windows. Even when sand blasting it to cut it broke the glass was even sandwiched with plywood and still broke. The tempered glass in cars is cut before being heat shaped and tempered.
 

shortbus

Joined Sep 30, 2009
7,841
I forgot to mention earlier. A couple of months ago I got a new phone and then ordered one of the case and a "tempered" glass screen to go with it. And shortly after my phone fell out of my back pocket while getting into my SUV. The phone hit the pavement and the tempered glass broke, not the screen. I'm not sure if there are different things that are called "tempered glass" but the screen protector broke like no car window tempered glass, just broke into three pieces not the 'nuggets' like a car window. So those thin screen protectors may be able to be cut, wish I'd have kept the pieces to experiment on now.
 

jpanhalt

Joined Jan 18, 2008
10,080
I would think thickness might make a difference. It certainly does when cutting borosilicate glass. Whether scissors under water would work may be a different story. As I mentioned, that does work with borosilicate (aka Pyrex or Kimax),but so does ordinary wire screen in air. Think of the latter as a very coarse grinder.
 

crutschow

Joined Mar 14, 2008
25,256
My understanding of true tempered glass is also that it cannot be cut, as it will completely shatter if you try.
The glass is heat treated so that it is internally under a lot of balanced stress, which makes it very strong.
But any scratch will suddenly relieve the stress at that point, which unbalances the rest of the stress, causing the glass to break into a zillion pieces.
I once had a large rectangular patio table with a glass top sitting in my open patio. One day we had a hail storm. The next day I noticed a pile of glass rubble under the table with no piece bigger than about 1/2 inch.
I assume the glass was tempered. :rolleyes:
 

jpanhalt

Joined Jan 18, 2008
10,080
OT:
When I did scientific glassblowing, we had crossed polarizers to examine our work to see where severe strains were. Strains showed up as a variety of colors, and we would flame anneal a bit more to relieve the most severe strain before putting the whatever into an annealing oven. (If a part was too strained, it could break during the annealing process.)

I never looked at tempered glass that way, but I'll bet it is quite colorful. Might make a nice wall decoration for nerds.
 

MisterBill2

Joined Jan 23, 2018
6,717
Polycarbonate plastic is a bit more scratch resistant compared to acrylic and only slightly more difficult to work with. Ordinary woodworking tools can be used carefully.
My experience with regular polycarbonate plastic is that it scratches very easily and then looks ugly. And in addition it is much more difficult to polish so that it looks good. And it is very hard to get a good sharp cutting edge on a polycarbnate knife blade. But they do not trigger metal detectors at all.
So if appearance matters then use real glass of some kind.
 

LesJones

Joined Jan 8, 2017
2,687
A source of thin non toughened glass could probably be obtained from a small picture frame. You could cut this with a normal glass cutter. (You might even find a picture frame with the glass near enough to the size that you want.)

Les.
 

Thread Starter

AlbertHall

Joined Jun 4, 2014
10,230
The hole the window is to cover is 23mm x 14mm. I wouldn't bother with covering it except this is the control box for my electroplating tank and so there will be the acidic solution around and so the box and everyting on the outside of the box is plastic to resist this solution. No solution should get on the box but stuff happens so I need to be sure that no solution can get into the box. If the window gets scratched, as long as I can still read the ammeter (three digit, 1A, as on ebay) then it doesn't matter.
 

MisterBill2

Joined Jan 23, 2018
6,717
For an opening that small a piece of window glass sealed with good silicone adhesive should be adequate. And it could be installed either on the outside surface or the inside surface of the enclosure. The benefit of installing it on the outside is that the integrity of the seal could be observed very easily.
 
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