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Thread: How Do You Cut Pyrex Tubing?
10-23-2008, 09:50 PM #1
How Do You Cut Pyrex Tubing?
I have a project that will require me to cut short sections o 1 1/4" OD with 1/8" wall thickness Pyrex tubing. I may be able to buy the lengths pre cut. If not how is it cut? I thought about an abrasive wheel and also thought about a carbide saw on my mill. The first seemed to be a better idea than the second.
This is an important project. My wife is on my a** to fix the landscape lighting in our yard. The globe, for some of the broken lights, seems to be made from Pyrex tube.
Thanks for your help and suggestions.
10-23-2008, 10:06 PM #2
I could be mistaken, but in chemistry class we just scored the glass with a small triangle file and then snapped the glass on a table edge. Be sure to protect your hands with a towel or heavy gloves.
10-23-2008, 10:12 PM #3
If you know anyone that does stained glass work, they will probably have a diamond bandsaw and can cut it for you. If you want to buy a diamond saw, google lapidary supply. You can buy 6" diamond saw blades and use them on an arbor either like a table saw or on a bench grinder with a suitable fence.
10-23-2008, 10:31 PM #4
Come to think of it, that is exactly how we did it in chemistry class. I am trying to make it like a hard plastic but it is really glass.
Many years ago, I make some highball glasses from thick wine bottles. I remember cutting the glass with a glass cutter and polishing the edges with a torch. Beyond that, I do not remember much about how I did it. I was in college and most likely drank the wine before I made the glasses; however, the wine I drank in college had a cap and not a cork. The bottles were also thin glass. I think I got the bottles for the glasses from a restaurant.
These fixtures are make mostly from copper plumbing parts. I will try to post a pic tomorrow when I have some light.
Yall may have seen the news reports of the terrible beating of a young newscaster in Little Rock. That happened two blocks from my house. Something like that is an incentive to fix your lights.
10-23-2008, 10:45 PM #5
10-23-2008, 10:55 PM #6
Landscaping lighting, with globes only 1.25 inch in diameter??
I'd probably chuck the tubing up in the lathe, with rubber sheet under the jaws.
Then put a glass cutter or diamond point in the toolpost and scribe it all around.
Single scribe *only*. Don't go over the first scribe a second time.
Then tap on the cut.
The old trick of wrapping a string soaked in gasoline around the glass and then
setting it on fire, probably won't work with pyrex, given that it has lower thermal
expansion coeficient than most other glasses.
10-23-2008, 11:02 PM #7
I don't think Pyrex will break with a score around it like the soft glass used in the things
you have been doing in chemistry class. Better figure on "grinding" it off.
10-23-2008, 11:18 PM #8
Now I remember how I broke the tops off the wine bottles for glasses. It was the string and gas trick. I got the idea for some really neat glasses, made from hand blown bottles, my dad brought back from Italy after the war.
The 1 1/4" globe protects the bulb and there is a 6" wide cover, that looks like a VC hat, over the Pyrex globe. They are are around a sidewalk and patio. They only stick up about a foot and a half.
A 1" piece of copper pipe, with a 1 1/4'-1" reducer on top, sticks out of the ground. The bulb fixture, is held in the large end of the reducer. The Pyrex globe fits in the top (large end) of the reducer. The cover fits on top of the Pyrex globe. I will post a pic tomorrow. I feel this project will go well into the weekend. Digging dog(s) is not good for low voltage lighting.
10-23-2008, 11:22 PM #9
Heavy wall pyrex tubing can be scored then the just under red hot end of a pyrex rod may be pressed onto the score. The thermal expansion will propogate the crack around the tubing. This leaves a sharp jagged edge on the tubing that should be wet ground smooth or at the least fire polished.
The way the cuts are done cleanly is with a wet saw like a Pistorius. These have a large (14-16 inch) fine abrasive blade. The blade is very porus. Water jets on both sides of the blade cool things and wash away the glass dust slurry. There is a slight chip out at the end of the cut. The saw has a sliding table and the glass tubing is held by hand during the process.
The closest thing to the proper saw is a tile saw. You might be able to do the job with a wet tile saw. Everywhere I ever worked we had a Pistorius. We either fire polished the ends, ground them on a wet belt sander, or left them as cut.
Large universities have scientific glassblowing shops that can make quick work of your job. Auto glass shops will have wet belt sanders if you cut the tubing yourself.
10-23-2008, 11:40 PM #10
Thanks for the additional info. I think I found pieces that will fit from McMaster. I may be able to find some of the missing ones if they were not hit with a lawn mower. I have found, almost, all the tops. Below are two of the three culprits. Fortunately, they have outgrown most of their digging and chewing.
One is a Boykin Spaniel, JD, and the other is a "champion golden retriever", Sikes. Look close at he BYD (big yellow dog). Sikes ain't no champion golden retriever. A yellow lab jumped the fence. We were puppy sitting Sikes for a charity event. The event was canceled, due to an ice storm, three years ago. Aretha Franklin, a BBD (big black dog) is not shown but equally guilty.
10-24-2008, 10:44 AM #11
plug the end, fill with light oil to level you want to make the cut, plunge red hot iron in [dont touch the sides] ping it be cut, works on bottles too, you learn some funny skills in a lab.
also gauge glass [picture glass also] immerse in water with a touch [2 drips] detergent, cut wityh a big scissors [underwater]
if stuck with rod/tube/sheet, score with a broken sparkplug, honest the white porcilain bit cuts glass with ease.
store your glasscutter in artists turpentine, makes cutting easy.
10-24-2008, 11:41 AM #12
You learn something new every day.
10-24-2008, 12:47 PM #13
seems like I remember cutting glass tubing this way. score a stress riser groove around the tube. block one end, water tight. twist a loop of copper wire around the tube, in the scored groove, & twist the ends into a pigtail. not too tight, but snug. secure the tube in a vertical position, inside some sort of vessel, like a bucket, & fill the tube almost to the score with water. allow the tube to sit a minute, you dont want the scored area wet. Now, heat the pigtail with a propane torch, to transfer some heat into the loop of wire. now, the idea is to raise the water level in the tube quickly, above the heated wire loop. maybe plunge a wooden dowel in, which is what we did. you dont want a splash, just a quick rise in water level. The cool water hits the hot groove, & it fractures. how much heat is enough? I don't know, this was many years ago, & I was a spectator, not the operator.There may be a learning curve. And remember, wear eye protection.