# Cutting Glass Test Tubes



## shred (Dec 4, 2010)

This one's come up a couple times recently and I ran across some pictures, so here's my lathe test tube cutting method. It's possible to cut tubes accurately like this.







The tube is gripped lightly in a collet (if it doesn't fit a handy collet, wrap some tape around it to fit a larger size-- all the forces are and must be very low for any of this to work). You could probably chuck it as well with appropriate tape padding.

A Dremel with standard cutoff disk is placed in the toolpost (I use a handpiece extension since it's much easier to clamp up in a QC holder). Protect the lathe from grinding and glass dust with some paper towels.

Run the lathe at a fairly slow speed and turn on the Dremel (I spin them opposite directions, but it probably doesn't matter much). Feed in very very slowly, trying to keep some oil in and around the cut as you go. 

The drill bit down the center of the tube is a long 'aircraft' drill held in the tailstock to catch the cut off piece and prevent it from running amuck or getting lost in the chip pan. Deburr the glass lightly on a diamond hone.


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## kendo (Dec 4, 2010)

Hi Shred
       Great idea, i will have to store that one away for the future.
       Thanks for sharing.

                     Ken


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## Kermit (Dec 4, 2010)

You don't need to 'cut' the tube all the way through.

Once you have scored the line into the glass all around, you apply a micro torch for a few seconds right on the score line. The tube will seperate itself and you can smooth down the cut edge with the torch if you wish.


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## Quickj (Dec 4, 2010)

Thank you for this. It is very timely as I broke a test tube displacer cylinder yesterday (See my post Dropped an engine),
and I will need to do this very soon. 

It is exactly what I was planning to do, except I have a diamond cut off blade for the dremel. I have attempted to cut glass tubing in the past for things like small drip oilers etc. and have had limited success. 

When I find the proper diameter test tubes, I will give this a try and let you know how it goes.

Jim in Minnesota


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## robwilk (Dec 4, 2010)

I recently tried this myself but through impatience i tried holding the dremel in my hand and rest on the lathe and cut it free hand with the lathe turning slowly . You might be surprised to know i didn't cut it straight and in the wrong place. oh:
So i have to do it again . 
I have a flexi drive like what you have used that i can clamp easily. Why didn't i think of that the answer was right in front of me. oh:
Thanks for showing us what you did. :bow:

Rob.....


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## Powder keg (Dec 4, 2010)

I'm going to try this next time I need to cut one. This guy gets the best results I've seen. Might have to make one of those doodads? This same method should work the same for test tubes.

[ame]http://www.youtube.com/watch?v=sFXngPx3w3M[/ame]


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## rleete (Dec 4, 2010)

Test tubes are a different animal than wine bottles. Heat a wine bottle with a torch, and you're likely to get a shattered bottle. Test tubes are meant to be heated.

Jan Ridders has cut lots of test tubes, as evidenced by his fantastic engines. He recommends the dermel in the lathe method, and wetting with turpentine.


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## Powder keg (Dec 4, 2010)

It still might be worth a try? There is always more than one way to skin a cat. Who knows, This might work better?


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## itowbig (Dec 4, 2010)

cool ill try it


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## rleete (Dec 4, 2010)

Sure, give it a shot. Hey, the worst that can happen is you have to drink another bottle of wine!


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## shred (Dec 4, 2010)

I've done score-n-snap a bazillion times on various glass art projects and the guy in the video has a pretty good way of doing it (you can also carefully squeeze or tap the bottle to run the score), but there's still a good chance of an uneven break that way as glass doesn't always fully follow the score. By grinding all the way through you get a very nice controlled and square cut. It's only a few minutes to cut a test tube with a dremel.


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## sunworksco (Jan 13, 2011)

An old plumber's trick is to soak cotton string in lighter fluid then wrap it around the glass tube on a pre-marked cut line.
It will snap easily on the mark after the glass has cooled.
This method was used to cut Pyrex laboratory glass drainage tube.
Regards,
Giovanni


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