Starting to drill tank (literally)

[hllywd]

As you found thin glass is a little more difficult to drill without cracking it but not impossible once you get a feel for it. It doesn't seem right but I use a few more RPMs and an extremely light touch at the end on all thicknesses.
I had a 3/4" chip flake off on the 29 I'm using for my sump, that's as close as I've come to breaking one (in about 20 holes). That hole turned out to be in the wrong place so I'm patching it and taking a "do over"...

Tim