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How to cut Sight Glass Tube?

I am doing some preparatory work on refurbishing the boiler for my IP Jane/PPS Janet rebuild, and I noticed that the top part of the sight glass tube was broken inside the holder.

This has been removed, and I have some spare glass tube with this boiler. However it is too long.

So how do I cut this sight glass tube to length, making a nice clean cut so it fits into the recessed cup of the holders?

score it all the way round the diameter with a dremel cutting wheel and then tap it. it will break around the score line.

Roger seems to be away at the moment, but he mentioned cutting glass tubing the other day.

While I have a purpose-made tubing cutter, Roger's way (the old way) does the same thing.

With a sharp and hard triangular file, wetted with turps or kerosene, preferably,
file a score mark all the way around the glass.

Then break it inside a cloth to protect your hands.

If the score is there the glass will break nice and clean.
It really need be only a scratch deep enough to catch your fingernail in;
that is, you don't have to file all that deep.

It works like cutting ceramic tiles, as you say just a scratch is enough. You must have some pretty hard files to mark glass, i would have to use my diamond files to do that.

I cut the tubing like Reid describes above with the edge of a file...though I just make one firm scribe and then wrap it in a few layers of rag and just snap the glass tube with the thumbs.  

To remove the sharp edge, I just hold the glass against a piece of Emery paper (very fine sandpaper) and take off the sharpness.  I have also used a dremel to do this with a rotating sandpaper disk.

I've not tried torching the end of the glass to melt the sharpness off, will give that a try next time.


OK thanks for your quick postings.

I found several references to glass tube cutting for laboratories on the internet, and this one covers the bending and fire polishing as well -

I'll use the remaining piece of the broken tube to practice on.

Thanks for your help.
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