Gang, Got a piece of glass tubing (similar to Pyrex) which is .490 ID, .625OD and I need to cut a piece about 11/16 long. File won't touch it, glass cutter won't do it, have been trying to score the outside with a thin "cutoff wheel", which scores it, but the stuff won't "snap off" as expected... just shatters, even past the score mark. Am I going to have to cut completely through with the cutoff wheel to do this? Ken.
Try a diamond wheel.
John
Have you tried scoring the outside with a sharp carbide scriber and snapping? It's possible the cutoff wheel is making too smooth a cut so the crack doesn't propagate as expected.
Best regards, Spehro Pefhany
sounds like borosilicate glass tubing
nasty stuff to cut in short lengths
mcmaster sells a nice little handheld cutter that helps immensely,
I still buy extra tubing when making sight glasses at work , they don't always break nice and clean
Sounded like sight glass material to me, too. I've never tried cutting something that short. I've always assumed the vendor cut them with a wet saw, especially the larger diameter ones.
Other approach (besides a diamond cutoff wheel) is to score around it completely with a carbide scribe. Basically you mount the scribe in a v-block type thing and rotate the tube (end up against a stop) to score around it.
Then wrap a piece of nicrome wire around the score and bring it to red heat.
Alternatively wrap a gasoline-soaked string around the scribe mark and light it on fire. Outdoors of course....
Jim
================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ==================================================
Glass tubing cutter. American Scientific and Surplus
Item #91921 GLASS TUBE CUTTER $7.95 / EACH
Half inch is tough to cut with the notch and bend method. A piece that short is not for the beginner.
There is something wrong here because even the cheapest triangular file will notch even quartz.
Is that 11/16" or 1 1/16"? Any Pyrex I've ever encountered would scratch with a file and break cleanly, but I've not cut anything quite like what you describe for dimensions, that's almost gauge glass thickness. I'd say it was time for a diamond wheel and a lot of water for cooling. I've also seen a jig for cutting thick-wall glass tubing for lasers using a hand hacksaw and a chunk of banding iron for a blade. Abrasive compound was used for the actual cutting media. Messy, any way you cut it.
Just thought of another way I'd seen for cutting big carboys and bottles. You use a diamond and scribe all the way around your cut area, wrap with nichrome and heat the area up with a Variac for current control. Then take a wet rag to the scribed line and it should crack through. Worth trying.
Stan
Once you score it, but it under water before trying to snap it off. I have had good luck with very thin glass under water.
After reading all this over and all the methods that "might" work I'd say take it to your local rock shop or any rockhound. The diamond saw could whip out a dozen of these in short order without all the headaches.
Koz
Stan Schaefer wrote:
You beat me to it, Koz. But before using your diamond blade, be sure to pack the tubing (anything will do; I use wet paper towels) to minimize breakage.
Good luck.
Sounds like the tubing is old. The older glass gets the harder it is to cut clean.
Try a small diamond cutoff wheel in a dremel tool. Score it all the way around.
Sounds like a job for a glass saw... a 'wet' table saw with a thin abrasive cut off disk. Water coolant is sprayed on the wheel just ahead of the cut. Most have a ball-bearing sliding table to hold the glass. Short or thin sections are do-able, but care must be used.
A wet tile saw might work, with an appropriate fine and thin saw disk.
Dan Mitchell ==========
A good suggestion, and an old glassworkers trick. Glassworkers usually wet the knick before tring to 'snap' a scored glass part. This somehow allows the break to progess easier. I've heard it stated as a 'surface tension' issue, with glass being a supercooled liquid. Whatever. It does work. Water, or more usually a drop of saliva, does the trick.
Dan Mitchell ==========
I read a textbook about glass. Very informative. Glass dissolves in water. It can help release tension in the surface of tempered glass when applied to scratches. My wife got first hand knowledge about this. When wiping down a glass cutting board (how stupid-a glass cutting board!) it exploded. Just went bang. As she was gently wiping it. What was most interesting is that glass itself becomes a good solvent when molten. And dissolves the furnace walls. ERS
Hanging on the wall at my local hardware store is a funny looking set of pliers with a gauge that slides and locks into place with a thumbscrew and on one jaw is a glass cutter. It is used to cut glass tubing to length for boiler sight glasses. ( and big coffee pots)
This I remember an article about - think it was SciAm in the days when it was less glossy.
The water molecule is just the right size to fit down in the crack in glass at the point where the crack starts. It helps the crack along at the molecular level, sort of a physical catalyst - that's why you don't need a lot.
Other molecules they tried of similar molecular weight were too big or too small and they didn't have the same effect.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.