Using metal CNC mill to engrave glass?

[zaebis]

I need to engrave a picture and some text onto 6x9 inch glass squares. So I was thinking if it would be possible to do on a conventional CNC mill.

1. has anyone done it? is it even worth trying?

2. what is the spindle speeds needed for the occasion?

3. what kind of endmills / bits do I have to use for that?

4. what kind of depth of cut are we talking about while engraving a glass?

[Tweakie]

"Diamond drag" comes to mind. The spring loaded tools are relatively expensive but last forever and are good for glass and metals.

Tweakie.

[dano9700]

Hi Zaebis,
I'm also trying to learn glass engraving at the moment. Like Tweakie said, a burnishing attachment is your best bet, along with a rotating diamond cutter. Since the attachment is spring loaded, you don't have to worry about depth/pressure settings, just give yourself a few mms leeway and the spring does the rest...
As for the speeds, I'm still working that out myself, but all the recommended rpms I've heard are around the 10k-20k range.

Still, I'm having trouble getting consistent results unless I use a very low feed rate, like 2-4 mm/sec. Faster than this, the cutter misses alot of areas. I'm not sure if my cutter is bad or if the glass I'm burnishing is low quality, or maybe a combination of both.
Maybe someone has some additional advice on this?

[Tweakie]

Dano,

It is usual to coat the glass with a thin application of a wetting agent or detergent just prior to engraving. (otherwise any surface finger marks can cause problems).

Tweakie.

[dano9700]

I've got that covered--my machine has a water circulation system that keeps a steady flow of water on the engraving area. Actually I wonder if I'll get more consistency without the water, since the burnisher seems to glide right over areas without affecting the glass.