Cutting Into Tempered (Toughened) Glass

No.

I'd grind the groove in prior to tempering the glass.

Shrinkage? Don't know.

It will shrink, by how much, one has to research.

Toughened glass: A wonderful material, but with an "Achilles heel"www.picams.com.au/.../Toughened%20glass%20-...SimilarYou +1'd this publicly. UndoFile Format: PDF/Adobe Acrobat - Quick View
In a typical glass batch there will be one 5 µg inclusion per tonne of glass (an average ... After this the inside gradually cools, solidifies and contracts. .... Once the nickel metal is all consumed the nickel sulphide inclusion will slowly shrink as it ...

I suspect that an infrared laser could do this but I seriously doubt this to be cost effective.

As for your reflow question during tempering, I suspect some reflow is probable but how much and where will have to be determined by trials. I am more concerned that your groove will cause your glass to break during the tempering cool down process.

"As for your reflow question during tempering, I suspect some reflow is probable but how much and where will have to be determined by trials. I am more concerned that your groove will cause your glass to break during the tempering cool down process."

I too hold the same view.

A diamond or carbide glass cutting tool will do it in most cases provided the glass temperature is kept under control with a liquid coolant while cutting.

Dear All, Many thanks for the replies. Just a little more detail:

I am going to use low Iron glass for its colourless property. The item is a squre plate 85mm x 85mm x 5mm.

The groove is required in the 5mm (the edge) thickness of the glass, so that means there will be 2mm border along the 10mm borders and the 1mm borders will be in the long axis of the 85mm length - am I making sense??

Do you still feel there would be a cracking risk?

Many thanks.

Yes.

The surface of the glass is in a different tension than the middle of the glass. Cutting that tension will cause the glass to break.

Pick a different way to mount your slide.

There are two different kind of tough glasses.

The safety glass used in american cars. They are layered with plastic. When broken, the plastic glued on layer keeps the whole layer as one, minimizing iniury.

The safety glass used in european cars is one piece. Its surface is heat treated to put it under tension. When broken, due this tension it does not produce slivers, which are likely to cut you badly.

Obviously the two glasses behave differently in grooving.

The first one (not being under tension) does not care, and takes grooving fine.

The second one (under intentional high tension) will explode spectacularly.

It matters, where the glass under question was made.

You are confusing laminated and toughened glass

Laminated glass bonds a layer of plastic between two layers of glass - it is NOT toughened, when broken it splinters, but the splinters are held together by the plastic layer. It will crack very easily, but not shatter.

Toughened or tempered glass has its surface cooled quickly causing very high stresses in the glass. This makes it very strong but when that high tension surface layer is breached it will shatter.

Back to the original enquiry, I do not believe it is possible to mill or grind a groove in toughened glass without it shattering, and I am not sure that it would be possible to successfully do it before the toughening process.

It may be possible to pre-form a lip (90 degree bend) along each side before or during the toughening process, but by far the easiest approach would be to bond a metal channel to the glass after toughening.

Mounting holes can be pre-formed along the edge the flat toughened glass plate before or during the toughening process (my daughter's car side windows have one on the bottom edge for mounting to the window winder mechanism.

See this----- http://www.cncinformation.com/CNCBlog/glass-engraving-on-high-speed-cnc-routers/

That is a very impressive display of their high speed CNC work! It might do the trick for this fella, but I would suspect that it might take several passes with different size/shaped bits to get a perfectly square "groove". Actually, IF as I suspect, the purpose of the groove is to put some sort of rubber or silicone seal at the edge, then square may not be the optimum shape, and a rounded groove would be much less of a concern, especially at the corners.

However, a closer look at the machine in the video reveals that it is designed for working on flat stock only. There does not appear to be any way to accommodate working on the edge of a plate of glass. But, the folks at the UniTech high speed CNC works may have more tricks up their sleeve, than what they displayed on that video. I would be interested in finding out if they can solve your problem.

If not, then you may have to resort to designing your own mold, and making the plate of glass with an edge groove molded into it. You are apparently trying to do something that no one has ever done before, and in that case it may have to be solved in a very unique manner.

Look at the edge of the glass being engraved, it is laminated NOT toughened

Never tried it, but hot rodders tell me they cut tempered auto glass with a sand blaster without it breaking. You would then have to polish the groove if needed. -- JHF

Auto glass is tempered on the side and the back window. The windshield is never tempered, only laminated. If the first responders have to break a window, they will get you out of it through the side, which shatters into tiny little pieces. The front is laminated to keep you from getting cut into ribbons in a collision.

As far as cutting tempered auto glass...remember, it is designed to shatter when you touch it with a sharp object. A saw is a sharp object. It is the very devil to modify a sheet of tempered glass. I would not bother, too risky.

I know all that. As I say, I have only heard of them doing it. I asked one what he was going to do about the glass on a chop job in progress, and he told me no big deal, cut it down with a sand blaster. I don't know if the truck is finished, but I am going to find out. I am curious now. Someone commented as if it is a difference in European or American glass. Never heard that, as far as I knew it was as you stated, lam for windshield, tempered in sides and back. I once threw a rear window on a trailer of junk, and it survived the landing, but a few minutes later a wheel landed next to it, missing it, then tipped over and barely touched it and it shattered as designed. It was interesting because a lot of junk was loaded in top of it, putting a lot of stress on it without it breaking, but once a corner broke, it want all the way! -- JHF

Cool!!!!

Get untempered (annealed) glass.

Misumi has dimension configurable soda-lime, quartz, borosilicate

http://us.misumi-ec.com/us/ItemDetail/10300270570.html