i'm looking for a real way to cut the end off a bottle?

Machine Shop is The Only Way To Go.....I Cut My Own Glass On The Lathe With A Diamond Saw Blade. Nice Clean Straight Edge And You Can Bevel, Chamfer, or Round The Edges To Your Liking. Oh And By The Way Did I Mention I'm A Machinist And I Have Access To All The Materials?

you can try a tile water saw. i use the water saw to cut glass tiles and it works great . the only thing is it puts small chips on the edges but you can sand them down. hope this helps......homedepot makes cuts for like 1 dollar.....oh yea make sure and were goggles

They used to make kits to make drinking glasses out of wine bottles as well as make holes to turn bottles into lamps.

I would try a hobby or craft store and ask if they still make them. It was a sharp scratchy thing that would make perfectly straight lines to create a flat surface for a drinking glass or perfect circles for holes where a cord and light fixture could be inserted.

a ceramic/diamond dust file works well and faster than you'd think.