Hi Tony

I've been experimenting with cutting gauge glass tube to length for hydrostatic lubricator sight glasses that have to seal on the end cut face. These are 10mm dia so smaller than yours.

As Baz suggests the most sucess so far has been diamond cut off wheel in a dremel mounted on the lathe toolpost, cutting very deeply into the tube wall until it's almost through and it will then break off easily. I've tried scoring the tube with a diamond file without much luck, the dremel has the best results although the cut ends still need a trim as in this application the tube needs to seal on its cut end face.

To get the end faces flat I've been using a diamond sharpening stone with a guide to keep the end square, good job I bought lots of glass tube as initially the atrition rate was very high, I only spoil about one in four now!

One tip you might find handy is once you have cut your first successful tube to the perfect length with nice smooth, square ends is not to let it roll off the bench and tread on it. Don't ask me how I know that!

Dave

Edited By Dave Wootton on 16/04/2022 17:25:16

I've had a suprising amount of success by just sharpening an HSS cutting tool to a knife edge point and turning the glass in the lathe. I wrap the tube in tape to protect it from the jaws, but a better way would be some sort of soft jaws as it can be a trial to get it concentric this way. I cut the end off of a pyrex test tube this way, but usually I cut normal glass.

You just gently introduce the cutting tool at a 90 degree angle and the glass cuts a vee which you can then tap gently to break once its deep enough. Playing a flame over the cut edge works for normal glass I think with pyrex you would have to use an abrasive grit paper to get the end sweet.

I used the diamond wheel and faux dremel – still took a lot longer than expected and couldnlt get the tool perpendicular – but it worked. Glass tube held in collet chuck.

I've never tried this, but I've seen it written that putting oil (I think, might be water) in a bottle to part way up, then plunging in a red hot poker will produce a good cut. Of course this possibly wouldn't work with Pyrex, which is more tolerant of heat stressing

Link to a Youtube video of cutting glass tube with a hot wire. (although a bit too long like a lot of amateur videos) https://www.youtube.com/watch?v=oU0ryjs-Tas

And a video of the score and snap method.https://www.youtube.com/watch?v=4ukVa0oW0xA

Edited By Paul Lousick on 17/04/2022 22:49:05