More on my glass drilling experience...
Ugly, ugly! Breakout from drilling too deep and the pressure causing breakout.
With the hole you are drilling full of coolant, it is really difficult to judge how deep you have drilled. My drill press has a quil stop but I did not want to trust it.... But there is an easy way to tell for sure. Make a depth gauge...
A fine ball end stone in your variable speed drill cleans up your hole in just a few seconds. Be sure to drizzle coolant...
To my amateur eyes, this is perfection!
