This instructable shows the jig I made to cut glass bottles. The method I use is from Jor2daje, here is the link: https://www.instructables.com/id/Easiest-way-to-cle...
The method uses a torch and something to rotate the bottle while heat is applied. Jor2daje used a lathe which I do not have, so I had to make my own apparatus. It is essentially an axle on a block of wood.
Also, make sure to protect your eyes! I was wearing chem goggles.
Step 1: Materials
All of the materials used to make this jig I had on hand. They consist of wood, screws, washers, a steel bar, metal wheel, ball bearing, a housing for the ball bearing, and masking tape.
Step 2: Wood Platform
You want to make a platform that allows the bottle to hang in the air when it rotates. Once you screw in the ball bearing housing and slide the metal rod through, I taped the side that would inserted into the bottle in order to prevent it from cracking the bottle when the bottle is cut. Attach the metal wheel to the other end of the metal rod. This allows you to spin the bottle at a controlled speed.
Step 3: Example Cuts
Step 4: Rig Upgrade
I added a "wheel system" to my jig to support the ends of long bottles. You can see it in the video below:
I will add more pics of the wheel system. Break happens at 3:28