The key with drilling glass is to GO SLOW!!

It may take a while.. take a few breaks, smoke some bowls..

Don't push to hard or it will crack..
Don't go to fast or it will crack..
Don't get anxious towards the end or it will crack and you will have wasted a whooole lotta time..

But if everything comes out good you could have a kick ass new peice.. My favorite bong is one me and a buddy made one weekend.. Used a Corazon tequila bottle.. It's like they made the bottle FOR stoners to turn into Bongs..

Anyways... ill stop ranting... But good luck and post some pics up here when your done