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andy_b
12-23-2006, 07:35 PM
i'm working on a project and need a few pieces of glass about 3"x12". i have one of those small metal tools you score the glass with and then supposedly break it off. well i now have a lot of pieces of glass in my garage, but sadly they are more useful as daggers than pieces i need for my project. :)

so how do you actually use one of these tools? i recall my grandfather using one years ago, but he is no longer around and i obviously do not have the method down. i'm just looking for how a person at home would cut a small piece of glass, not using some water jet or other commercial tool.

any advice is appreciated.

andy b.

motomoron
12-23-2006, 08:00 PM
Well, first you design your shape and export is as a .dxf to your waterjet table...

Seriously, you place your pattern under the glass, or mark it with a fine point Sharpie, and with the glass on a FLAT hard surface, scribe on the lines.

For straight lines I put a length of wire, like 3/32 music wire if you're fancy, or the straight bit of a coathanger if you're not, aligned under the scribed line.

A gentle push downward on both sides yields 2 pieces of gless.

http://www.wikihow.com/Cut-Glass

...is good info.

Good luck-hope you finish for X-mas.

PHiers
12-23-2006, 08:02 PM
Andy,

When I was just a young lad we were taught to cut it this way. Dip the cutter wheel in kerosene and score the glass, then put a wooden dowel under the scored line and break the glass over that. It worked well as I remember although I have not cut any glass for a long time.

CCWKen
12-23-2006, 08:02 PM
Use a straight edge and your tool to score a line in the glass. Press hard. It should sound like you're ripping cloth. Make sure you go edge to edge. Once the line is scored, use the ball end of the tool and lightly tap along the score. Place your straight edge under the glass, along the score, with your piece unsupported. Briskly press down, in one motion, along the unsupported piece.

Alistair Hosie
12-23-2006, 08:08 PM
You want to spend 20 to 30 bucks on a good diamond glasscutter and cut as described one score only not two and you will be fine cheap glasscutters work fine once or twice then they are fit for the dumpster follow this and you won't go wrong .Alistair

speedsport
12-23-2006, 08:12 PM
It's fairly easy, use a straight edge, a drop of oil on the tool, medium firm pressure, one continous stroke, tap the backside with the ball thats on the other end of the tool, you will see the crack develop, lay a wooden dowel or something similar under the score mark and press down on each side. Practice until you get the feel for it.

claudev
12-23-2006, 08:17 PM
These instructions are for a novice. Put a few sheets of newsprint on a flat surface. Place a piece of sheet glass on the newsprint. Lay a straigntedge across the sheet where you want the cut. Using the glass cutter agains't the straightedge (finger grip on the cutter) scribe a line across the glass. Put a small dowel under the scribed line and press down firmly on both sides of the scribed line. You should now have 2 pieces of glass.

Notes: 1) Start out with known good clean glass - new single strength. 2) Glass cutter must be sharp - recommend new. 3) Tempered glass cannot be cut - will only shatter. 3) Do not retrace your cut line - if you do results will be erratic at best. 4) Some people like to dip the cutter into a light lube just before cutting - kerosene or WD-40. 5) You can find books at home centers and libraries. 6) Glass cutting is easy to learn.

As you gain a little experience you can move into thicker glass and free hand cuts and curves, even stained glass work.

lugnut
12-23-2006, 09:33 PM
Andy, the most important thing when cutting glass is: the cutter and Glass need to be CLEAN. Having the glass at room temperature also helps. I do a little Stained Glass and a hobbie and if you are going to cut a lot of it, I would suggest you buy a good oil filled cutter. Any ways here is a link to site that has a pretty good instruction for cutting glass.
http://www.refinishfurniture.com/glass_cutting.htm

good luck:)
Mel

miker
12-23-2006, 09:40 PM
I have used a 4 inch angle grinder with a Masonary wheel to cut quarter inch thick plate glass. Came out OK.

Rgds.

J Tiers
12-23-2006, 09:44 PM
What if you want a ROUND piece of glass... a wheel-like piece?

I used to be decent at cutting straight, but never did get the hang of getting curves,to work, let alone circles.

Of course I have seen professional glass cutters whip a score down a pattern, curves and all, and KLICK.... two pieces of glass, perfect pattern. Dunno how they do that... no dowels, no tapping. They have a hold of it, and suddenly there are two pieces.. :confused:

lugnut
12-23-2006, 10:20 PM
Cutting circles, It can be done, but not in one cut. Outside curves are do-able by taking off small sections at a time. Inside curves are not so easy. Done mostly by chipping out material with glass nibblers. You can cut a pretty wavy line with a little luck and practice. I cheat a little on real close circles and curves because I have a diamond band saw. Not really a band but a 5 diameter wire ring coated with diamonds and it runs on soft rubber rollers. Also runs in a water bath. But it lets you cut from any direction. The rings cost about $60 bucks so you want to be very careful. This saw will cut almost any material.
Mel

PTSideshow
12-23-2006, 10:50 PM
Fisrt thing I was taught about cutting glass is not to be worried about breaking it.
next clean glass new glass will cut clean lines, old glass it's a crap shoot.
place a number of shhets of newspaper on a solid flat table top. As many as cuts you want to make.
To score the line use a good wheeled glass cutter with light oil between pulling the score lines. (the oil washes glasschips away from the wheel)
with starightedge or pattern underneath pull the line towards you with the cutter 90' to glass ( the tail /handle of the cutter between two fingers resting on the web of the hand)
pull with a slight downward pressure so the sound is like frying bacon. (I really don't know why but it works.)
One stoke per cut only two or more will crack and splinter the glass.
your chose of dowel wire, or yard stick or table edge to split. you can tap the opposite side of the score line or not.
with a fast sure motion snap the waste glass down ward.
remove one layer of newspaper to make next cut.
the very fines plinters of glass coming off the score line and snapping will cause uneven pressure points under the next piece of glass.

Cutting a circle two ways first way is a winning bar bet.
you need a bucket of water a piece of single strength glass to fit in the bucket. And a pair of old fashion tinsnips, the kind that looks like scissors NOT THE AVIATION SNIPS.
Place the glass under water put the tinsnips in the water make sure both the tinsnips and glass are under water. cut a circle out of the glass. when finished bring it out. Collect winnings send my 5%.
Circle will be a little lopsided.
It works because glass is a slow moving liquid and not a solid, also that water and glass share the same specific gravity or close to it.
It did take me a couple of trys before I could do it to make it look easy and fast. Must be new glass.

Old glass if standing on one edge slumps with age so one end is thinner than the other. In real old houses the windows will be thin at the top and thicker at the bottom.

The second way of cutting a circle is place the pattern under the glass draw your circle. than score lines to big the glass down to a octogon or more sided shape. Than cut along your patten line for a few degrees carring the score out to the edge of the glass. repeat till you have your circle. With practice you can do it with out all the trimming. That is the way we cut out the glass windows for the fire alarm pull stations in the public buildings.

To cut S curves or following curves it just takes practice and a smooth steady scoring pull. Use to freak people out at bars and other parties cutting a 6"x6" glass in to multipul long S curves so they fit like a puzzle.
Fletcher makes grosing pliers that have bar running down one of the jaw sides to split the score line they also call them running pliers with slight curve in the jaws to split the score.

To cut plate glass or thicker glass than double strengh use a dull glass cutter. it will work better as it will score the glass line down and not splinter over the surface. I was taught by a fellow that came over from Belgium after the war 30 plus years ago.
I had purchased a brand new 5 dollar Fletcher glass cutter to cut some plate for the wifes new curio cabinet shelves. when he seen it in the package. He wipped it out and started running the working end over the cement floor. I like to had a heart attack, when I calmed down he explianed to me that only a dull cutter will work on plate. And it did.
hope this helps. will look for and post some pic of the pliers. :D

PTSideshow
12-23-2006, 10:54 PM
For under $30.00 US you can buy a circle cutting compass deal at some of the better stain glass places or web sites.http://www.delphiglass.com/fusing-flameworking-jewelry/
http://www.waleapparatus.com/ are two of the larger sites

Evan
12-23-2006, 11:58 PM
Plenty of good advice already given here.

I have cut thousands of pieces over the years including scientific borosilicate as well as ordinary soda lime glass. There isn't really any trick to it, just a matter of becoming familiar with the material. As has been said, do not try to score over the same line twice, it will not work.

One thing that hasn't been mentioned is that after scoring snap the glass immediately. The score "heals" at the molecular level and after even a few minutes will not break as cleanly. That's why your windshield doesn't fall to pieces even though it may be badly scratched.

About the old idea that glass is a super cooled fluid: It is not. It is an amorphous solid. Although it is not crystalline it is still a solid as it undergoes an energy transition as it cools where the binding energy of the molecules exceeds the kinetic energy. Below that temperature, which varies depending on type of glass, the molecules do not have sufficient kintetic energy to be mobile and so it cannot flow, however slowly. The molecules are locked in place just as surely as crystals are. The difference is that there are no defined fracture planes which makes it possible to cleave the material in any direction.

For breaking a piece after scoring pick it up by the edge. The score must go all the way from edge to edge. Place your thumbs on either side close to the score on top with your fingers below and with a small but firm action snap the piece as if trying to bend it down on each side of the score.

Wear safety glasses of course.

andy_b
12-24-2006, 12:28 AM
thanks all, this is some GREAT advice! i don't need to have the glass pieces by Christmas, so i'll have to pick up a new cutter tuesday or wednesday and give it another try.

andy b.

darryl
12-24-2006, 02:57 AM
My method for clean and straight cuts- clean the glass, especially if it's old. Clean well, both sides, then dry it. Then score, but only once. Then lay the glass on a clean flat surface which has a good straight edge, putting the scored line directly above that edge. Grasp the outside edge of the glass and give a sudden firm downwards pressure. An alternative I sometimes do is to raise the outside edge of the glass after positioning it, keeping the one edge still in place and in contact with the flat surface, then firmly bring it down. The weight of the outboard piece of the glass does the job. For plate glass, this is my preferred method.

Did anybody mention to wear gloves and eye protection-

I saw a guy cut a circle out of our window one day as they began removing it to replace with new. He first put a plunger onto the glass, then made one quick 'drawing' of a circle around it with the glass cutter, then just jerked the plunger away. The circle of glass came away cleanly, leaving a nice looking hole. It was faster for him to do this than for me to type this paragraph.

Evan
12-24-2006, 03:59 AM
The reason I prefer to snap the glass as I described is because the break then starts at one edge and runs to the other. When glass breaks the crack propagates at the speed of sound in glass. It follows the score because when recently made the energy of the molecules in the bottom of the score is higher (hotter) and the bonds are weaker.

If you break it by applying pressure more or less evenly the crack may start in multiple places and be slightly less predictable as the sound waves can reflect from the edges and cause it to change direction. If you do snap it over an edge apply the pressure at or near one end of the score.

Ian B
12-24-2006, 07:06 AM
How do you cut glass?
With a rawn mower...

Your Old Dog
12-24-2006, 08:50 AM
Evan is right about not lollygagging around after you make the score. I normally don't need any aides to snap the glass after I cut it as I do it within a couple seconds of scoring it. Using this technique I've been able to cut out many of the letters of the alphabette on new glass. (I had tons of scrap to practice with working at a glass shop as a kid)

If you're talking laminated glass then you score both sides, do a little wiggle and then poor lighter fluid into the cut and light it to warm up the laminate which gets like goo with some heat.

Evan
12-24-2006, 10:37 AM
Evan is right about not lollygagging around after you make the score.

Best decribed as a slit and run or maybe a drive by scoring.

I got my initial practice when I was young working for a scientific glass blowing shop and since then I have made quite a few leaded and foiled glass pieces. Funny thing is that I don't have a single piece of my own work left around, I gave them all away. One of these days I should do an inventory of my fancy glass and think of something to make. I do have a pic somewhere of a nice terrarium I made years ago, I'll have to see if I can find it.

You can dress the edges of cut glass on a belt sander or by hand with some silicon carbide paper. This will make it less prone to cut although cuts when handling glass are rare.

dicks42000
12-24-2006, 11:43 AM
A word of advice....

Evan and others have already alluded to how & why scoring glass to cut it works. Glass is highly "notch-sensitive"
If you've ever done any lab stuff, you probably learned to cut glass tubing with a triangular file, too.
Ever done any glass tempering ? Amazing how tough glass can be made by causing it's outer surface to contract..."pre-stressing".
Some of us just have to go a little further...Do Not ever try to cut tempered glass with a masonary wheel on an angle grinder....You can melt the glass in the cut, but that strain energy has to go somewhere....Fortunately the pieces aren't sharp, but the clean-up sucks....
Have a good Christmas.

A.K. Boomer
12-24-2006, 12:07 PM
Plenty of good advice already given here.

I have cut thousands of pieces over the years including scientific borosilicate as well as ordinary soda lime glass. There isn't really any trick to it, just a matter of becoming familiar with the material. As has been said, do not try to score over the same line twice, it will not work.

One thing that hasn't been mentioned is that after scoring snap the glass immediately. The score "heals" at the molecular level and after even a few minutes will not break as cleanly. That's why your windshield doesn't fall to pieces even though it may be badly scratched.

About the old idea that glass is a super cooled fluid: It is not. It is an amorphous solid. Although it is not crystalline it is still a solid as it undergoes an energy transition as it cools where the binding energy of the molecules exceeds the kinetic energy. Below that temperature, which varies depending on type of glass, the molecules do not have sufficient kintetic energy to be mobile and so it cannot flow, however slowly. The molecules are locked in place just as surely as crystals are. The difference is that there are no defined fracture planes which makes it possible to cleave the material in any direction.

For breaking a piece after scoring pick it up by the edge. The score must go all the way from edge to edge. Place your thumbs on either side close to the score on top with your fingers below and with a small but firm action snap the piece as if trying to bend it down on each side of the score.

Wear safety glasses of course.



"There isn't really any trick to it", I cant believe you say stuff like that and then say that you have to break it quick because it "heals" and then go into all the molecular properties, I cut a few peices of glass in my day but had no idea i had to hurry to break it, --- the things you learn on this site, its great to tune in with a morning cup of coffee and learn something new, one of my goals in life is to learn something new every day --- I gotta hand it to you Evan, i totally elect you as the guy who knows the most about most things...

A.K. Boomer
12-24-2006, 12:17 PM
A word of advice....

Evan and others have already alluded to how & why scoring glass to cut it works. Glass is highly "notch-sensitive"
If you've ever done any lab stuff, you probably learned to cut glass tubing with a triangular file, too.
Ever done any glass tempering ? Amazing how tough glass can be made by causing it's outer surface to contract..."pre-stressing".
Some of us just have to go a little further...Do Not ever try to cut tempered glass with a masonary wheel on an angle grinder....You can melt the glass in the cut, but that strain energy has to go somewhere....Fortunately the pieces aren't sharp, but the clean-up sucks....
Have a good Christmas.


I had an old volkswagon and one day i was playing with a piston pin (always had engine parts laying around inside the car) and tapping it on my drivers side window that was almost all the way rolled down, i was useing the circumference of the pin (not the end) and was lightly tapping it in a downward motion on top of the window (probably to some rock and roll), I did not think anything of it , very light, all the sudden it was like someone fired a gun, there was a huge explosion and it took me a second to figure out that i no longer had a window, tempered glass is amazing, and this kinda goes along with what your saying, it is under lots of stress...

Evan
12-24-2006, 01:47 PM
With tempered glass all you need to do is puncture the highly stressed "skin". That produces a stress concentration above the yield point that travels at the speed of sound throughout the glass. Ever notice interesting patterns in back or side windows on a car while wearing polarized glasses? Those are the stresscons. They are very near the yield point. You can break a tempered glass window on a car by tossing a ceramic chip from a spark plug insulator at it, a favorite trick of auto B&E specialists.

When making laboratory glass articles they must be annealed after the hot work is done. This is done in an annealing oven and the glass is heated to just below the flow temperature. It then must cool very slowly over hours. When finished it is examined by placing it between polarizing filters. Any stresscons in the glass will cause a polorization rotation of the light and shows up as different colors in the glass.

Wirecutter
12-24-2006, 02:12 PM
Like it's been said, make sure you're not trying to cut tempered. I tried this on the carpeted floor of a living room once - it was a pane from a storm door with damaged frame. I scored it and put a length of pipe under the score. Pushed down on both sides to break at the score/pipe and POP!

Spent the next few hours vacuuming little bits of glass from the carpet. Not one had a volume greater than a cube 1/8" by 1/8".

I also remember those old "RonCo" (or similar) TV commercials years ago selling a whiz-bang glass cutter. The demonstrator was cutting straight lines, curves whatever. He'd score the glass, pick it up, and snap a perfect break, all in less than about 2 seconds. Of course, when you do it at home and get all slow and deliberate, it mostly works, with a few annoying and dangerous little burrs. Or maybe the line is nowhere near where you scored and you have to look for another pane of glass.

I got a chance to play with some "scrap" glass and a cutter in a picture frame shop once. I donned the gloves and glasses and tried to imitate the demonstrator in the RonCo commercial, cutting and snapping very quickly. Guess what? Every cut was perfect, unless I didn't score all the way to the edge.

It really is true that you need to be a bit brisk and confident about it. Wear safety stuff, of course. It helps to have enough material on hand to be able to afford to screw up once or twice.

-Mark

stuntrunt
12-24-2006, 02:42 PM
If the glass is not too thick, you can cut it with scissors when you hold it under water...

lugnut
12-24-2006, 03:34 PM
One of the handiest tools I use when cutting glass is the glass breaking pliers. You can adjust them for the thickness of the glass and how much breaking force you use. After scoring the piece of glass from one edge to the other, you simply place the pliers over the score line, at one edge and squeeze gently. After some practice you can control the speed at which the glass is broken and see the break as it crosses the piece of glass. In the photo of the end of the pliers you can see that the center is higher than the edges thus forcing the break.
http://img.photobucket.com/albums/v671/lugnut/DSC00272.jpg
http://img.photobucket.com/albums/v671/lugnut/DSC00271.jpg
Mel

andy_b
12-26-2006, 11:05 AM
I had an old volkswagon and one day i was playing with a piston pin (always had engine parts laying around inside the car) and tapping it on my drivers side window that was almost all the way rolled down, i was useing the circumference of the pin (not the end) and was lightly tapping it in a downward motion on top of the window (probably to some rock and roll), I did not think anything of it , very light, all the sudden it was like someone fired a gun, there was a huge explosion and it took me a second to figure out that i no longer had a window, tempered glass is amazing, and this kinda goes along with what your saying, it is under lots of stress...

i used to work with a friend restoring old VWs. the rear side windows are tempered as well, and you should've seen some of the bends we'd get in them without breaking when we pulled them out prior to body work. it was like pulling out pieces of lexan. the funny thing was, if you tried to pry one out with a screwdriver, you'd just barely touch the edge and it would shatter.

oh, i have to go to the Depot today for a glass cutter. hopefully tonight or tomorrow i'll try my hand at cutting another piece.

andy b.

speedsport
12-26-2006, 01:34 PM
I remember seeing a demostration when I was a kid where the guy took a glass lab beaker and used it to drive a 16 penny nail through a 2x4, and then dropped a bb into it and it shattered, the inside and outside were tempered differently.

nheng
12-26-2006, 02:41 PM
You can cut circles with a glass cutter mounted on a compass like setup (suction puck, adjustable length rotating arm with carrier for cutter). Never done it and don't care to try :) I've had a local glass shop cut clean circles in 1/4" thick glass. For about $10 each, the 4" circles were clean, to diameter (but not machinists tolerances, mind you) and had the edges nicely and uniformly beveled. They replaced missing microscope stage glass and looked original.

I've seen a small glass cutting saw at a artisans craft fair last year. It was smaller than your smallest Delta or Sears tabletop bandsaws, had its own water feed and the blade was diamond. I was impressed at the speed of the cut but had never seen anything like it before. Den

stuntrunt
12-26-2006, 03:30 PM
Proxxon sells a quite decent bandsaw (Micro band saw
MBS 115/E) which you can have a diamond blade for. With the (very high tech) coolant system it cuts glass at a fairly good rate...

Evan
12-26-2006, 07:54 PM
For about $10 each, the 4" circles were clean, to diameter (but not machinists tolerances, mind you)

You would be suprised at the tolerance commonly held in scientific glass blowing. It isn't uncommon to hold tolerance to a few thou depending on device. Standard tolerance for borosilicate glass tubing such as Ace Trubore is +-0.0004" on the ID. I have never worked glass to those tolerances but the master glassblower in the shop I worked in did.

aboard_epsilon
12-26-2006, 08:10 PM
if it's old glass you're cutting you'll never cut it right ...as it has lots of fine scratches in it ...it will try to follow these rather than the scratch you've created whatever tool you're using.

all the best..mark

Cheap Jon
12-26-2006, 08:46 PM
First time on this board, I have been lurking for a long time. I needed to cut some small windows for fire valves at work, used my tile cutter and it worked great.
Jon

ptjw7uk
12-28-2006, 12:31 PM
Cut new glass should be very easy just cut with constant pressure best with a diamond dipped in kerocene (parafin in uk) does OK
Now for the difficult bit old glass, clean surface as best you can then score surface as before then use the side edge of the cutter to tap the underside of the glass along the score small sharp raps will cause the cut to travel through the sheet then work along the score to the other side. Has worked fine for me even cutting 1/2" thick sheet but it took 2 of us to break it over a dowel rod out of 6 cuts only had 1 curvred cut not bad as it was cullet otherwise!!!
Peter