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Dave C
04-28-2018, 11:19 AM
I'm looking for ideas on how to cut the bottom off of this 4 1/2" diameter, glass vase.
http://bbs.homeshopmachinist.net/attachment.php?attachmentid=2783&d=1524927179
I'm thinking about turning a wood plug with a groove in its face to accept the rim. The OD of the plug would be greater than that of the glass so it could be chucked in the lathe. A rubber stopper between the glass bottom and the live center would keep the whole works together so that it can be rotated by hand. So now the question is how to proceed. Is my idea OK so far? What to use to score the glass, hss or carbide, cutter profile? All ideas and criticisms accepted and appreciated.

danlb
04-28-2018, 11:46 AM
There are many ways to do it. One is to use heat. Soak a cotton string in lighter fluid. Wrap it around where you want it to break. Light it, let it heat, then plunge into cold water.

http://www.instructables.com/id/How-to-cut-a-bottle-with-string-and-nail-polish-re/


Dan

oxford
04-28-2018, 11:50 AM
Never did it but I have also seen score with a glass cutter and then the hot/cold water treatment. There are lots of YouTube videos on doing this and it does not require machine tools.

danlb
04-28-2018, 11:52 AM
Many of the techniques that score it also rely on heat induced stress to make it crack along the line. The third one on this page
( https://www.wikihow.com/Cut-a-Glass-Bottle ) uses a cutter to score the glass, then boiling water to induce the crack.

Use caution when using a lathe. If the forces get to great the glass will shatter and shards will go everywhere. Don't ask how I know.

Dan

BCRider
04-28-2018, 12:12 PM
Another option with less risk to the glass cylinder would be to use a tile saw, which has a diamond blade, to cut the glass. Try it first with a cheap drinking glass to get a feel for the cutting so the round vase doesn't try to spin. Rig up some way to hold it against spinning if the tendency is strong.

Dave C
04-28-2018, 12:13 PM
Using the lathe was a means of making the question relevant to this forum. I wasn't planning on running the machine. It would be hand rotated to effect the score line. My concern is what to use to score the glass.

J Tiers
04-28-2018, 12:36 PM
Abrasive cutting, or the score and hot wire technique.

GrayTech
04-28-2018, 01:48 PM
Drop a largish coin in the vase and swirl it untill the bottom drops off. Works surprisingly well. Google cutting bottle with coin for more info.

Juiceclone
04-28-2018, 02:15 PM
Use a real glass cutting tool to score the cut. I experimented with carbide and diamond "points" but it seems that the tiny wheel on the glass tool fractures the glass deeper than just scratching with something sharp. They occasionally worked, but mostly not.

SGW
04-28-2018, 03:17 PM
I might try a Dremel tool with one of the thin abrasive cutoff wheels, with gentle pressure of the cutoff wheel on the vase as it's rotated. If you put the lathe in low back gear you could probably rotate it under power. Cobble up a way to attach the Dremel tool to the toolpost and slowly feed it in against the rotating vase. Don[t rush it.