Instructions
* Print and bolt (or glue, melt, whatever) the parts together as per the picture.
* Fit a bearing of whatever size you like.
* Clamp a glass cutter in place.
* Adjust them so that a bottle can easily turn on the two points of contact.
* Adjust the conical plug so that the cutting wheel is at the height you want to cut away.
* Turn the bottle through ONE rotation on the blade to make a single small score all the way around.
* Carefully dribble some hot water over the score line.
* Dribble some cold water over the score line.
* Continue to alternate the last two steps until the heat stress drives the fracture through and the bottle comes apart.
* Sand/grind down any remaining sharp edges.




