Not really cutting, but read on…
Just had a large reputable glass co install some large picture windows. About 6’8″ h x 8’6″ wide, two layers of 1/4″ tempered glass with an insulation gap. Took 6 guys, they estimated it weighed about 525#. The glass was made to the exact size specified (they did the measuring) and the frames were made to the same size, thus there was essentially no room to get the glass into the frames. The lead guy, 20+ yrs experience, took out his RO sander and shaved down the top edge of the glass, and they were able to squeeze it in. I asked him later about what he did, and he said that since the glass breaks into 1/4″ pieces they can take off as much as 1/8″ if necessary. I didn’t know that…is he right? In my case, all he really did was clean off the excess glue and goop from the edge of the sandwich.
Do it right, or do it twice.
Replies
I believe he's asking for trouble. I was an engineer designing a process to temper glass windows for a specialty product. I'm not a ceramic engineer by education, so I learned a lot from others. In thermally tempered glass the compressive surface layer is about 1/4 of the thickness. So, for a 1/4" thick pane, the layer is about 1/16". If you go deeper than that the glass shatters. As for the edge, I never had to deal with that in my situation, so I never asked how deep along the edge it goes. So, not knowing, if it were me I would not do it.
Of course, he may have done it successfully before. Even if he did not understand what he was doing, his experience may have told him it was ok. His reasoning based on the size of the pieces is certainly all wet, though.
I would not jam glass into a frame so tightly.
really did was clean off the excess glue and goop .....
ou ought to be OK then.
when a kid, tried to cut/grind/drill tempered glass, always a shattering experience.
>>he said that since the glass breaks into 1/4" pieces they can take off as much as 1/8" if necessary
Did you really believe him? That's funny though.
If he takes off as much as 1/8", then if the glass does break, the pieces along the edge would be 1/8" instead of 1/4". Now do you believe this?
Is this a residential installation? That's a monster piece of glass.
The glass is that tight in the frame? hope it does not move or settle much.
Here's a pic. The client wanted a clear view of the ranch...the dining room table will be in front of the glass.
I didn't really believe him, although he didn't appear to be BS'ing me...I think he was telling what he really thought. He did explain that the glass was not jammed into the frame, but there was barely enough clearance to get it in...once in it was fine. And it's warrantied for 5 yrs so hopefully any problems will show before then.
Well, my picture allowance is used up...now I get to figure out how to delete attachments. I read the current thread and will try that.
Do it right, or do it twice.
Edited 10/16/2003 10:07:56 PM ET by ELCID72
Came with a warranty that covers beltsander modifications?
Joe H
ELCID72,
What is "the current thread"? I just had the same "used up" problem come up & haven't been able to get a reply.
Fonz..."deleting old attachments" in General Discussion.Do it right, or do it twice.
Reminds me of a shed I saw on a piece of land that was for sale. The owner had taken a piece of tempered glass about three feet high and four feet wide, installed it with only one flat 2x4 of knotty rough sawn lumber as a "header" with rafters right on top of it. (Shed was about 10 feet wide) A FIVE FOOT WET SNOW DIDN'T BREAK IT!!!
Structural glass?Any jackass can kick down a barn, but it takes a carpenter to build one.
Sorry to say that the glass is now under compressive tension and it's gonna break at the slightest provocation... That glass needs expansion room. It's too tight in the frame.
BTW glass is nick sensitve.
Who ever invented work didn't know how to fish....
compressive tension .....
please explain that term, as in tension compressed concrete???
It is what it says
Who ever invented work didn't know how to fish....
Maybe compressive stress? Compressive tension seems to be like a double negative in English, and that'll get red marks on the paper.
Do it right, or do it twice.
OK...
Who ever invented work didn't know how to fish....
I don't know if this would apply to a sealed unit, like you're described; but, the mirror guys 'scribe-fit' wall-to-wall mirrors with a belt sander all the time. The ones I've seen all use those little 1" wide portable belt units.
Phill Giles
The Unionville Woodwright
Unionville, Ontario
Phill, I think those mirrors are all plate glass.
Plate glass is very soft and easy to work with (belt sanding the edges works fine).
Tempered glass is highly stressed and that gives it the strength, but even the tinyest nicks can provide a place for that stress to go above the limit of what the glass material is capable of resisting and then it shatters.
When tempered glass shatters the chip size is made by the shock wave as it bounces from one face of the glass to the other. The thickness of the tempered surfaces (think of the glass as a glass sandwich, the hardened glass is the bread and the meat is untempered "plate" glass). When the tempering is done evenly the chips are all the same size.
Since the tempered glass provides its own stress, it only takes a nick (no need to apply any outside load, just a nick) and off it goes!
Norm
First glass that size should be sitting on at least 1/4" rubber pads.
I replace alot of insulated glass and clearence should never be an issue. Many units when made in a shop are slipped, meaning both glass sheets are not perfectly in line. this is ok because clearence around all edges on a unit that size should be no less then 3/8".
Cleaning off high spots in the with a razor blade is not a problem but grinding the glass tells me it's not the correct size. Any settlement, expansion or contraction is going to spell trouble. If you don't get broken glass I'll bet you'll get seal failures but it'll take more then 5 years for them to really show themselves.
The glass breakage size is really some left handed BS that he obviously had to learn in the 20 years he hasn't been able too master reading a tape.
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Edited 10/17/2003 8:04:05 PM ET by GEOB21
The glass does need room around it for movement. They make rubber pads for this purpose that are about 1/8" thick. Glazing suppliers have them. You should have either reordered the glass or routed out the frame to fit it. It will likely have a very short lifespan now. If the glazing company did the measuring make them change it out.
I did absolutely nothing except call them to the site and writte a check. On things like this, I don't want any involvement in case something happens, so they can't say I gave the wrong dim or whatever.
Here's a pic...
Do it right, or do it twice.
got some news for ya...
you wrote the check ...
you are now the glass GC ...
it's your problem now.
You bought the responsibility with that check.
Hope you added your 15% to their total to pay for the time you have to spend to fix their mistake and make things right now.
JeffBuck Construction Pittsburgh,PA
Fine Carpentery.....While U Waite
Jeff, you're right with respect to my relationionship between the owner and the glass co. But my point was that I let the glass co do everything their own way, so the measure and fab and installation is all their responsibility. And what do you mean 15%? I add way more than that.
Do it right, or do it twice.
Back around 1977 I had a patio door glass shatter after about 2-3 years of installation in the house I built for us. It shattered for no aparent reason and was on an inside porch that was screened in so no sun hit it and no birds or stones hit it. I was in the kitchen where the door was when it happened. The glass company said it was from "tension compression" from when it was assembled at the factory with too little of a clearance.
I was surprised since it was an aluminum door because I assumed the frame would deflect before it would have shattered. The guy from the glass company said one never knows "exactly" how glass is effected when under compressed tension in any particular situation.
If that was the case, and is the case in this installation, I sure hope when/if it does shatter down the road, there are no people (or pets) standing next to it. Lawsuit heaven.