i have an old cd in my glove box.... i draw round it when marking out a waste pipe to cut round. also, i don't have a fancy set of hole cutting drill bits
, i make do with a large triangular bit that does any size up to about 35mm, it does struggle a bit with porcelain but if you make a pilot hole first with an ordinary masonary or tile bit, it works great. cheap as chips... i replace it every 2 or 3 months.