drilling 10 gallon?

[reefnut]

well i tried using a dremel to cut a 1 1/2 inch hole in a scrap of 5 mill today.i was about half way through and it cracked.i did not use any water just kept feeling how hot it was so i dont think it was a heat issue.i traced the hole and followed the outside of it to cut it out.the bit i was using was one made fore grinding glass and ceramics.and i put very little pressure on it.if someone has time can they describe how they did theirs.did u cut all the way thru from one side?did they use any kind of lube?did i use the right bit?it is green and about the sixe of a pencil eraser and it comes to a dull point at the end.