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blogfast25
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[*] posted on 17-11-2022 at 09:43
Hacking a test tube




test tube.jpg - 144kB


I've a fairly large text tube which I need to hack in two but I only need the 'closed' part. It's a 150 mm x 24 mm large tube, wall thickness est. 1 mm.

For a smaller tube I'd probably manage but for this size I'm sctratching my head a bit. I do have a diamond tipped lab glass cutter.

Any ideas welcome!




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mayko
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[*] posted on 17-11-2022 at 11:02


maybe you can slap together a glass cutting jig?
https://www.instructables.com/Simple-Bottle-Cutting-Jig/

I have also seen a method where a string is soaked in alcohol, looped around the bottle, and lit... once burnt, the bottle is plunged into cold water and the glass cracks around the hot ring. Might not work on test tubes though, depending on the glass




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Morgan
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[*] posted on 17-11-2022 at 11:10


Thin glass tubing tends to not break evenly when scored if it is a larger diameter. Maybe a dremel and diamond disk.
https://youtu.be/CfR966lIVAE

[Edited on 17-11-2022 by Morgan]
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Texium
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17-11-2022 at 12:44
blogfast25
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[*] posted on 17-11-2022 at 12:57


Quote: Originally posted by Morgan  
Thin glass tubing tends to not break evenly when scored if it is a larger diameter. Maybe a dremel and diamond disk.
https://youtu.be/CfR966lIVAE

[Edited on 17-11-2022 by Morgan]


Ah. Have Dremel, will try!

Thanks!




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[*] posted on 17-11-2022 at 18:07


another method is to heat the test tube where you want it to break and touch it with a cold metallic rod while the glass is still hot. The principle is that a thermal shock will start a crack to form at the desired location, which can be propagated around the tube by repeated heating/cold metal cycles until the tube breaks. Possible advantage over the Dremel might be less glass dust.

[Edited on 18-11-2022 by phlogiston]




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[*] posted on 17-11-2022 at 18:26


I have never had much success with the string/alcohol/plunge in water method on a bottle. I have not tried it for a TT.
It seems that the heating from the flame is not very uniform and not necessarily concentrated in a specific region to induce the thermal shock.
I have not tried this on a test tube, but I would expect it to be more difficult with a smaller diameter and with borosilicate.

You might try using a nichrome wire wrapped around the circumference. You can position it as needed, hit the switch and then plunge the TT into water after heat has been applied.

Whatever you do, a grind on a sanding wheel or heating the end in a flame would be a sensible second step to remove the sharp edge.
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[*] posted on 18-11-2022 at 05:00


Molten NaOH should do the trick as long as you dont need really smooth edges. But these you can proably fix with the Dremel.
Just dip the part you want gone in the lye.
Cackling like a madman as the glass melts is optional but I would :)




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[*] posted on 18-11-2022 at 17:46


This would be impractical and not worth trying but it came to mind as a way to eat/attack and maybe crack borosilicate glass test tubes.

https://youtu.be/ztrquSMI1tk

https://youtu.be/GE-NkVqUiHs

https://youtu.be/cFGejaYqM-c

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[*] posted on 19-11-2022 at 08:00


If you skip to the 1 minute 40 second mark there's a good example of "hacking a syringe" quite nicely with a dremel.
https://youtu.be/UtaECKAkS-E
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blogfast25
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[*] posted on 19-11-2022 at 08:26


Dremel is definitely my method of choice, to be tried 'shortly'.

Drizzling molten lye seems (potentially dangerous) overkill.




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[*] posted on 19-11-2022 at 08:56


When you do the dremel method, make sure to keep the bit and cutting surface under water to cool and lubricate it, and go slowly. Several years ago I had to drill a hole through a test tube using a dremel diamond bit, and that was key to success.



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[*] posted on 19-11-2022 at 10:39


Something like this at the 6 minute mark with water helps avoid cracking and you won't overheat the diamond bit or blade either. I have an extension for my dremel a little more electrically safe when using water. With a lathe to spin a test tube or tubing, that luxury offers quite a bit of control too.
https://youtu.be/sRVrDTMOsII
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[*] posted on 23-12-2022 at 13:45


I do this a bit for glasswork purposes. Scoring and breaking, or heating, is very unlikely to turn out well. There's a small chance you get a clean break, but it's just that: chance. Very unpredictable for diameters >10 mm or so.

Abrasion is the way to go. A dremel and diamond bit can work, but it requires a good dremel and a good tool bit. If both the chuck and the bit aren't very well centered and smooth, the run out you get will result in a situation where you're kind of smashing the glass with the tool every revolution. That obviously tends to crack things.

If you want the best chance of a good result, a diamond hand file is the way to go. It'll take a few minutes, but with a light touch you won't be subjecting it to any large and sudden forces that start up any cracks, and you'll have a clean and crisp cut.
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[*] posted on 23-12-2022 at 14:35


I used a diamond jigsaw blade to score a test tube in order to break it, and it worked very well
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[*] posted on 23-12-2022 at 20:47


Quote: Originally posted by blogfast25  





I've a fairly large text tube which I need to hack in two but I only need the 'closed' part. It's a 150 mm x 24 mm large tube, wall thickness est. 1 mm.

For a smaller tube I'd probably manage but for this size I'm sctratching my head a bit. I do have a diamond tipped lab glass cutter.

Any ideas welcome!


The best is a Dremel with a small diamond disc! I used the discs from the DIMAPA brand, not the Dremel brand. I have cut a large quartz reactor with them,absolutely no damage and even cut the crucible from a larger sapphire tube to the exact length.The cut is thin,the surroundings don't crack and the accuracy is very good.
https://www.dimapa.cz/50mm-diamantovy-kotouc-maly-10-ks-120-...

[Edited on 24-12-2022 by Admagistr]

[Edited on 24-12-2022 by Admagistr]

[Edited on 24-12-2022 by Admagistr]
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[*] posted on 14-2-2023 at 07:56


Quote: Originally posted by Texium  
When you do the dremel method, make sure to keep the bit and cutting surface under water to cool and lubricate it, and go slowly. Several years ago I had to drill a hole through a test tube using a dremel diamond bit, and that was key to success.


And don't forget to wear a dust mask.




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