On 4/15/20 2:12 PM, micky wrote:
In alt.home.repair, on Wed, 15 Apr 2020 05:55:16 -0700 (PDT),
wrote:

I am trying drill some holes in glass tile to allow the screws from a GFI receptical cover to seat properly. Purchased a 1/4" ceramic and glass bit and drilled a test hole in an extra tile. All went well.
Left it on the workbench and returned 1/2 hour later to find the corner had cracked off.
What went wrong ? Why would it do that ?
Thanks

Now that you know about water cooling, I'd drill a few more test holes
to learn what other possible mistakes there are.

It's sounds like you have a nice ?bathroom or kitchen?.

I'd seriously consider gluing the cover to the wall instead of using
screws. No risk of breaking a tile that's glued to the wall, especially
if you have only a few matching tiles to replace broken ones.

Ambroid cement would be good for this, sticks to just about everything,
smells good, dries fast, but is not so strong that you can't break it
off if you need to someeday. Sticks well but not so well that you can't
knock off whatever is stuck to tile if you need to that too. Only sold
at hobby stores. Not at Amazon





Did not see your suggestion until I posted similar advice