I was thinking of another of the 'many' projects I hope to do someday, and was wondering if anyone has chucked up a diamond bit into a collet on the mill and tried engraving glass? The glass I was thinking of is standard sheet glass (probably toughened) (10mm?)

I am assuming very light cuts. Glass would be held in with cardboard or rubber between clamps and table. Also clamps not tightened down hard. Plenty of lubricant. High RPM on spindle. Anything else you guys can think of???

Has anyone tried this? If so, how did it go? Is it even possible?

I've wondered about this too.

One thing, if you mean "tempered" when you say "toughened" I'm 99% sure that's not a good candidate for engraving. From what I understand tempered glass has a ton of internal stress that is only held together by a very strong outer layer. Breaking that outer layer will release the stress and completely shatter the whole piece if you even scratch it too deep, engraving is probably out of the question.

http://www.youtube.com/watch?v=qvRgklsm6so

Oddly enough, it's impossible (or at least very difficult) to tell if a piece of glass has been tempered or not.

Wow, that's good to know. I would say there's a lot of tempered glass in the home due to the safety aspect of it. It is harder to break, but when it does, there are no big shards of glass. The glass I had in mind is used for those sleek looking shelves in the home. The label says toughened, but I'm sure tempered is the same thing. Having said that, it's easy enough to go to my local glazier and get pieces cut up the size I want.

Very good and interesting info. Thanks for that.

If all your doing is trying to engrave shallow you might try using some type of resist that you can machine away easily without affecting the glass. Then you sand blast the glass to get your frosted look. You can even cut deeper into glass with sandblasting for a more 3-D look if thats what you want. As far a using tempered or not, not sure what would work best most likely like Hirudin said tempered wouldn't be best. I would think this would also be your fastest option.

I have done glass before at work, We buy the glass in sheets, do whatever work is needed, then send it to be tempered. Once the glass has been tempered you can no longer cut or engrave it.

i have blasted plenty of tempered glass, it does ok. just keep the pressure down and don't stay in one spot too long. regular plate glass works better, but it all depends on what you will be using the finished product for. i have used a roto zip to engrave plate glass and it works just fine, but only tried it on tempered twice, and both times the glass exploded on the table.

I've been wanting to try this with glass with a spring loaded diamond point.

I can see it now, after engraving, and I go to pick up the plate glass, all the little shapes that were engraved will fall out like stained glass pieces, lol!

Hmmmm.... now there's an idea...

Dave