More about Waterjet cutting

[Havi]

I was just thinking about asking you, when I found this interesting thread.

However,
my dilema / question is different.
I made a 'block' 1+1/16" thick, 10.5" diameter. It has nice air bubbles in it... looks OK.
I neglected to to dam it properly - it was dammed with stainless steal circle, and between the steal and the glass i put too short fiber paper. The firing lasted 33 hours, I believe it was a conservative schedule, and good annealing
The result is that the edges are not even, and they need to be trimmed to be straight.
Not so easy for me, even though I have a revolution saw. I do not trust myself to cut a circle on this thickness.

Not easy to find waterjet cutters here in this so very small country. Eventually I found one and talked to him today. Beside the price, which will not be cheap, he raised the question whether it will be possible to cut this piece, because he suspects that the glass is hardened after such a long firing.

I'd be very grateful for your advice and imput. Should I go ahead and have the glass cut to an even edge,
or -
What?


many thanks,

Havi

[Morganica]

Hardened? That's a new one--you can reassure him that this won't be a problem.

Waterjets make short work of soda-lime glass. The only issue will be whether the piece has any stresses from annealing or compatibility issues--waterjet seems to be really REALLY good at finding them.

I've had waterjet cutters edge several of my pieces, with only one failure (something got stuck in the cutter nozzle and it spit great big gashes across my piece that required filling and refiring). Usually you must be very precise in the shape (and location of that shape) that you want. However, as long as you want a standard shape such as a circle, oval, rectangle, etc., the cutter operator will usually help you set up the cut without requiring a design file. If what you want is truly a perfect circle, you should be able to specify the diameter of the circle to the operator, mark a center and start point on the glass (for positioning) and have it cut without too much trouble.

What you may have a problem with, though, is cutting through bubbles, which will mar the sides of the piece. Even if you polish the glass, the bubbles will show up as flaws--this has been an issue for me in the past with thick castings.

If you're leaving the sides unpolished, probably not a problem. If you are going to coldwork/polish the edges yourself, get a bar of soap and rub it over the cut areas to fill all the bubble holes with soap. Then grind and polish, renewing the soap as needed. Saves an immense amount of time later, when you're trying to clean all the cerium and stuff out of the holes.

One other tip: The water jet cutters I've worked with give you precisely straight edges and sharp, 90-degree corners against the surface of the glass. If you're going to grind and polish the edges, do yourself a favor and put a bevel on those corners before you start. The edges are REALLY susceptible to chipping.

[Havi]

Thank you Cynthia,
As always, I appreciate your response and taking the time to write it. Always enlightenning!

I meant TEMPERED GLASS - but my language was too poor to find this idiom.

I am asking myself if I should really do it

1. if it breaks - then let it break, it would have broken anyway. But it was a long time annealed, really conservative [following instructions I got in one of my classes at BE, last BEcon, not this one]

2. if the edges are to be opaque - then I might as well keep it the way it is now. One can see the marks of the fiber. Looks like some kind of design, actually.

3. I can trim it on my revolution jigsaw, and then WBS it, but it will need a lot of work

4. Hopefully Friday my blacksmith will be here to discuss some stands for some pieces, so I might here something encouraging from him too.

Thanks so much,
I'll try photograph and post it, but you wo'nt be able to see the crookied edges

Havi

[Havi]

Oh yes,

Thanks for the tip about the soap in the holes, I remember you mentioned it sometime in the past on this board.
At that time I used it and it worked for me!


Thanks again

H.

[DonMcClennen]

Havi.....sounds like a job for a wet belt sander! Won't that work for you? (much cheaper)

[Morganica]

Havi, I really doubt your glass is tempered--it's not a function of time since firing. If it were tempered, then you couldn't cut it or grind it without having it shatter. But if it's well-annealed, by definition it's not tempered.

Some waterjet cutting facilities will also polish the edges of the glass, so you might ask if that's a service they provide. But a waterjet edge will look like the edge you get when you cut glass with a good tilesaw blade, or possibly a bit finer. The smoothness will depend on the cutter. Most of the ones I've seen are pretty smooth, about like 220-grit, and I've sometimes had tiny chipouts on the underside.

What you might try as a first step is getting a powerful jet of water (as from a power washer), and really washing out the edges well. Let it dry, and see if that edge works for you.

If you do want to trim something that thick yourself, I'd probably start with the tilesaw, not the Revolution. I know Revolutions and bandsaws are supposed to be designed for this type of cutting, but that's a lot of glass. A good tilesaw has the power to reduce that load. Use a very fine blade, set the work up on the saw so that you're cutting a straight line on one side of the glass, tangential to a point very slightly outside the circle. Turn the piece 90 degrees and cut another tangent, and repeat for the other two sides. Then go 45 degrees from the first cut and make another tangential cut, repeat that. You'll wind up with an octagon-shaped piece, like this:

NOW use your Revolution (or an angle grinder/WBS or both) to trim it down to final size. Saves a lot of time and backaches. Other folk may do it differently.

[Bert Weiss]

Your glass is annealed, not tempered (toughened). 30mm is no big challenge. I have fused and waterjet cut glass this thickness, with no problems. As Cynthia says, a problem will come when the waterjet pierces a bubble. The space will fill with ground glass and be visibly flawed. If you can find a circle with no bubbles on the perimeter, that would certainly be best.

If the glass breaks from the waterjet, there were stresses in it, and you need to reevaluate your process.

[Havi]

GOD BLESS YOU - ALL OF YOU
You are so helpful.

Yes, Cynthia, a friend of mine here, suggested what you so wonderfully put in drawing. Only - the tile saw... is again a problem in this Holy Land.
I believe I could be able to find something here not too far. [There is a gravestones maker not far from here, I am sure he has a tile saw. I had him grind some broken shelves for me]

But I have to decide whether this is what I want.

All of a sudden I am full of work and full of projects to fulfill. Just was invited to share an exhibition here, where I live, with painter who is also a musician. She does watercolors - mostly blacks, my pieces will contribute the coloration to the whole exhibition. I am very happy about it, but want to acheive more - buld more pieces, accomplish all the ideas running in my small head. The opening is on September 20, and September all the High Holidays start here , which mean half of the time all businesses are closed. - So plenty of time to work piecfully at home, but much less time to have pieces finished - stands etc.

perhaps this is the opportunity to ask about how would I present my pieces - I'll post another thread about it.


I can not put to words my appreciation and gratitude for your help, now and always.

Many thanks,

Havi

[Havi]

Just wanted to update you................
After a long research here, and talking to many people, professionals and glassies - I had the impulse to TRY and WBS this piece - and see what happenns.
It worked not bad, in an hour I noticed some progress..
So I thought that some one stronger than me might do the job well enough, or at least I should TRY with someone else.

Today I had Yekhiel, a hard working person come to me, within 2 HOURS, he completely evened the edges of the piece....
At the beginning I had him work with my angle grinder - while I was holding the glass for him. I did so, because the hardest working disc was the one I had for that grinder.
Then he said he wanted to try working on the flat bed grinder... OK.... 120 grit diamond plated disc....
Then, he said he wanted to work manually... rubbing the glass with one 3m belt that I had torn sometime ago. By then the edges were even [straight?] already, Now he is cleaning it for polishing.
He will be back on Monday, I am sure the piece will be done on Monday.

However, working on the wbs I scratched the surface a bit, so I am thinking of erasing these scratchs with my rociprolap.

Seems, it will work, after all my

Thank you all again for your wonderful advises, that lead me thru my hurdles, time and again,

Many thanks,
Havi
I attach a photo of how it WAS, now the edges are straight! Sorry that the pic got in the middle of the text...