I bought a new 2'x3' x 3/8" piece of plate/float glass and its not flat.
Over the 3' there is a gap of .02" checking with a good straightedge. My No
7 plane actually rocks on the glass. The underlying surface is flat. I've
read that all plate glass is now the same as float so I don't think I bought
the wrong type.
I previously had (and cracked) a 1/4" thick piece that didn't vary by more
than .003".
What is a normal tolerance? Does thicker glass have greater tolerance for
error?
-- Mark
On Mon, 03 Oct 2005 18:57:36 GMT, "George E. Cawthon"
<[email protected]> wrote:
>Super cooled liquid is the standard saying. And
>glass does flow. No fairy tale. Actual
>measurements show that glass standing vertically
>for a long period is thicker at the bottom. Of
>course it does take a long time.
Howdy,
You might want to read:
http://math.ucr.edu/home/baez/physics/General/Glass/glass.html
Among other things, it indicates that the "flow" concept has
not been demonstrated.
All the best,
--
Kenneth
If you email... Please remove the "SPAMLESS."
Mark Morin wrote:
> I bought a new 2'x3' x 3/8" piece of plate/float glass and its not flat.
> Over the 3' there is a gap of .02" checking with a good straightedge. My No
> 7 plane actually rocks on the glass. The underlying surface is flat. I've
> read that all plate glass is now the same as float so I don't think I bought
> the wrong type.
That is a pretty large error. Normally glass thicker than 1/4" is made
by cooling it on a pool of molten tin. The tin melts at a lower
temperature than the glass and since a fluid finds it's own level if
not vibrated or disturbed the reason float glass is so flat. Nominal
is .001 over a 1'.
Obviously the stuff you got has to be rolled or allowed to sag once it
comes out of some rollers. Are both sides thin like this? Got a
micrometer to check the thickness around the parameter?
Second thought is to buy a B grade granite surface plate.
Alan
Mark Morin wrote:
> I bought a new 2'x3' x 3/8" piece of plate/float glass and its not flat.
Glass is very flat, but it's also bendy. Try placing your glass on a
layer of foam over a reasonably flat surface. If you take the forces
off it and let it float, then it should be flat.
Laminated glass and poorer quality toughened glass loses flatness, but
new float glass ought to be the flattest thing in the average workshop.
[email protected] wrote:
> My suggestion, look at Grizzly at the granite flats/plates, grade B
> flatness and very thick, works like a charm here for scary sharp,
> and I don't have to worry about how much pressure I apply while
> sharpening - I think I paid around $20 for a 9x13 one from Grizzly.
Ditto this, but if I were doing it again I'd get one that's 12"x18"
(three inches thick they are). This allows for a full sheet of 9x11"
abrasive to sit *flat*. The 9x12"s come with an eased edge on top, and
as such the surface tension of paper is lost along the edge when using
fluid to keep it in place. Plus, bigger is always better....right?
JP
**************************
Zero tolerance anyone?
Bruce Barnett wrote:
> "George E. Cawthon" <[email protected]> writes:
>
> > I already argued that a worker couldn't possibly
> > have determined the thick end and consistently placed that end on the
> > bottom. It is interesting that other use the thick on the bottom for
> > proof of glass flow and others argue it is thick because the worker
> > placed it that way. Guess both arguments are bullshit, which is what
> > I said.
>
> It doesn't claim that glass is always laid that way. Just that it's
> done SOME times, and I'm sure the urban myth wasn't started by someone
> using a micrometer. Since there is no evidence of glass flowing, that
> theory explains why some houses DO have "thicker at the bottom" glass
> better than any other theory.
>
Last I heard there were several known examples of window panes
thicker at the top.
Perhaps the powner's manual indicated that they sould be rotated
periodically, like tires.
--
FF
On Mon, 3 Oct 2005 16:49:45 -0700, "Mark Morin" <[email protected]>
wrote:
>I guess I was spoiled with my old 2' x 3' glass. I could put 6 quarter
>sheets on it for sharpening chisels. Is was also big enough to put belt
>sander strips on it for plane soles. I considered MDF but I use 3M spray
>adhesive and it comes off nicely when changing papers (maybe Formica-type
>top would be better, which I haven't tried).
>
>I checked the granite -- price goes up quickly based on size and really
>quickly based on shipping.
>
>I'm going to try another piece of glass before going the granite route.
>
>-- Mark
My Scary Sharpening station is an old marble window sill that was
removed from my mom's house when an addition was built. It seems
rather flat to me (not measurably off by my crude measurements and
certainly not off enough to rock a plane or a blade). It is about 3
feet or so long and wide enough for a sanding belt. Can set up a whole
range of grits from 80 to 2000 in small sheets at one time. When done,
it stands in a corner somewhere. Probably can find one somewhere where
a building is coming down or something.
Dave Hall
On Sun, 2 Oct 2005 17:54:37 -0700, with neither quill nor qualm, "Mark
Morin" <[email protected]> quickly quoth:
>I bought a new 2'x3' x 3/8" piece of plate/float glass and its not flat.
>Over the 3' there is a gap of .02" checking with a good straightedge. My No
>7 plane actually rocks on the glass. The underlying surface is flat. I've
>read that all plate glass is now the same as float so I don't think I bought
>the wrong type.
So use a piece of MDF, or your kitchen countertop, fer Crikey's sake.
>I previously had (and cracked) a 1/4" thick piece that didn't vary by more
>than .003".
>
>What is a normal tolerance? Does thicker glass have greater tolerance for
>error?
Good question. Glass does move; some say it's a liquid. I scratched my
new utility door window while removing the label. 2 months later I
noticed that the scratch had healed; it shocked the hell out of me.
Leave the glass on the table for a month and see if it has settled.
It may have been stored upright where it took a bow.
--
"Most Folks Are As Happy As They Make Up Their Minds To Be"
-Abraham Lincoln
-----------------------------------------------------------
www.diversify.com - Happy Website Development
> Good question. Glass does move; some say it's a liquid.
Thats an old wive's tale. Glass is amorphous, but certainly not liquid.
> I scratched my
> new utility door window while removing the label. 2 months later I
> noticed that the scratch had healed; it shocked the hell out of me.
>
I think you just looked in the wrong place.
I scratched a microscope lens 35 years ago. It is still scratched exactly
as it was then.
On Mon, 03 Oct 2005 18:57:36 GMT, George E. Cawthon <[email protected]> wrote:
> Super cooled liquid is the standard saying. And
> glass does flow. No fairy tale. Actual
> measurements show that glass standing vertically
> for a long period is thicker at the bottom. Of
> course it does take a long time.
Please read this:
http://tafkac.org/science/glass.flow/
Just because your science teachers told you it does, doesn't mean they
were right. The folks at alt.folklore.urban are damn good about
tracking things down, and if you have something that isn't covered in
their FAQs and is truly new information, they'd love to know about it.
On Tue, 04 Oct 2005 14:47:02 GMT, max <[email protected]> wrote:
> Glass is amorphous. The quick explanation is that is not a solid or a
> liquid.
Please read this:
http://tafkac.org/science/glass.flow/
Just because your science teachers told you it does, doesn't mean they
were right. The folks at alt.folklore.urban are damn good about
breaking things down, and if you have something that isn't covered in
their FAQs and is truly new information, they'd love to know about it.
On Tue, 04 Oct 2005 14:47:02 GMT, max <[email protected]> wrote:
>Glass is amorphous. The quick explanation is that is not a solid or a
>liquid.
>max
it's amorphous. the quick explanation is that it's a non-crystalline
solid, not a liquid.
I guess I was spoiled with my old 2' x 3' glass. I could put 6 quarter
sheets on it for sharpening chisels. Is was also big enough to put belt
sander strips on it for plane soles. I considered MDF but I use 3M spray
adhesive and it comes off nicely when changing papers (maybe Formica-type
top would be better, which I haven't tried).
I checked the granite -- price goes up quickly based on size and really
quickly based on shipping.
I'm going to try another piece of glass before going the granite route.
-- Mark
"Jay Pique" <[email protected]> wrote in message
news:[email protected]...
>
> [email protected] wrote:
>> My suggestion, look at Grizzly at the granite flats/plates, grade B
>> flatness and very thick, works like a charm here for scary sharp,
>> and I don't have to worry about how much pressure I apply while
>> sharpening - I think I paid around $20 for a 9x13 one from Grizzly.
>
> Ditto this, but if I were doing it again I'd get one that's 12"x18"
> (three inches thick they are). This allows for a full sheet of 9x11"
> abrasive to sit *flat*. The 9x12"s come with an eased edge on top, and
> as such the surface tension of paper is lost along the edge when using
> fluid to keep it in place. Plus, bigger is always better....right?
>
> JP
> **************************
> Zero tolerance anyone?
>
Got a sink cutout of granite from granite shop gratis, used for scary
sharp. About 12" X 18".
On Sun, 02 Oct 2005 22:35:39 -0500, [email protected] wrote:
>My suggestion, look at Grizzly at the granite flats/plates, grade B
>flatness and very thick, works like a charm here for scary sharp,
>and I don't have to worry about how much pressure I apply while
>sharpening - I think I paid around $20 for a 9x13 one from Grizzly
>
>John
Charles Spitzer wrote:
> and of course, all those pieces of cast glass that the egyptians carelesslly
> just left lying around are simply puddles by now.
An incredibly stupid comment, for a great number
of reasons. Do you know anything about Egyptian
glass making?
>
>
> i don't know where you got the above ideas, but you might want to recheck
> them.
>
>
I'm sure you don't because you are too lazy to read.
Toller wrote:
>>Good question. Glass does move; some say it's a liquid.
>
>
> Thats an old wive's tale. Glass is amorphous, but certainly not liquid.
>
>
>>I scratched my
>>new utility door window while removing the label. 2 months later I
>>noticed that the scratch had healed; it shocked the hell out of me.
>>
>
> I think you just looked in the wrong place.
> I scratched a microscope lens 35 years ago. It is still scratched exactly
> as it was then.
>
>
Super cooled liquid is the standard saying. And
glass does flow. No fairy tale. Actual
measurements show that glass standing vertically
for a long period is thicker at the bottom. Of
course it does take a long time.
Glass does heal. Anybody that works around glass
or just uses his observation powers knows that
freshly broken glass has much sharper edges than
broken glass edges that have been around for a
time. If that isn't enough for you, anyone that
uses a microtome (you know one of those things
that cuts very thin slices for microscope slides)
and uses glass for the cutter, knows that you
use a freshly broken surface. Let it sit around
for a while and you won't be able to cut as thin
slices as freshly broken, note we are talking
about slices less than 10 microns thick. Of
course, you could even more simply use a
microscope to examine broken glass edges. The
type of glass also makes a very big difference to
how fast it heals.
Nonetheless, I don't believe the healed glass
scratch in a window. Two months is too short a
time to possibly observe that; 20-30 years for a
very, very light nearly invisible scratch on
window glass, maybe but more likely 100+ years.
Probably was a scratch in the dirt on the glass or
maybe just a thin cobweb.
I've been waiting for 5 years for a scratch in a
new window to heal. Har. Har. Not really, the
house will be torn down long before that glass heals.
As for the microscope lens, it might be very hard,
heck it could be crystalline quartz, but not
likely. In addition, the scratch would have to be
on a vertically oriented plane to heal in any
observable way.
"Larry Jaques" <novalidaddress@di\/ersify.com> wrote in message
news:[email protected]...
> On Mon, 3 Oct 2005 10:27:16 -0700, with neither quill nor qualm,
> "Charles Spitzer" <[email protected]> quickly quoth:
>
>>"Larry Jaques" <novalidaddress@di\/ersify.com> wrote in message
>>>if you want it to be flat, you have to put it on something that is flat
>>>already.
>>>
>> You'd think he'd have straightedged the table he layed it on, wouldn't
>> you, before determining that only the glass was curved?
>
> ass-u-me. no, i'd not expect that.
From my original message ... "The underlying surface is flat".
Thanks for the vote of confidence. Is this where I say, "you'd think they
read the original post."
and you reply, "Ass-me. No, I'd not expect that" :)
Just to clarify, I measured it on my table saw top, my 8" jointer, and my
workbench ... all of which have been checked for flatness. But the real
indicator is that if the piece is flipped over, the bow likewise switches
from facing top to facing bottom.
-- Mark
Glass is amorphous. The quick explanation is that is not a solid or a
liquid.
max
> Dave Hinz wrote:
>> On Mon, 03 Oct 2005 18:57:36 GMT, George E. Cawthon
>> <[email protected]> wrote:
>>
>>
>>> Super cooled liquid is the standard saying. And
>>> glass does flow. No fairy tale. Actual
>>> measurements show that glass standing vertically
>>> for a long period is thicker at the bottom. Of
>>> course it does take a long time.
>>
>>
>> Please read this:
>> http://tafkac.org/science/glass.flow/
>> Just because your science teachers told you it does, doesn't mean they
>> were right. The folks at alt.folklore.urban are damn good about
>> tracking things down, and if you have something that isn't covered in
>> their FAQs and is truly new information, they'd love to know about it.
>>
>
>
> I read it and wasn't impressed. Just typical
> newsgroup bullshit and no scientific discussion or
> evidence. I did like the part that says that the
> greater thickness at the bottom of old panes of
> glass was due to original variation in thickness
> and that glaziers orient the thicker part to the
> bottom. I thought of this as a possibility for
> about 10 seconds before discarding it. First,
> most glaziers probably didn't give a damn how the
> glass was oriented and even if they did, they
> couldn't tell the minute difference in thickness
> without a micrometer on a consistent basis. That
> would howlingly be funny to see a guy in the
> 1800's using a micrometer on glass panes before
> glazing them.
>
> I suggest you use a microtome with glass knives to
> find out for yourself and propose a different
> reason for why a freshly broken edge will cut a
> thinner slice.
>
> BTW, I doubt that many of my professors considered
> or gave a damn about this burning issue. I'm sure
> there is plenty of data out
Amorphous, is that a new state of matter? I
though there were only four states of matter. I
am being sarcastic.
max wrote:
> Glass is amorphous. The quick explanation is that is not a solid or a
> liquid.
> max
>
>
>>Dave Hinz wrote:
>>
>>>On Mon, 03 Oct 2005 18:57:36 GMT, George E. Cawthon
>>><[email protected]> wrote:
>>>
>>>
>>>
>>>>Super cooled liquid is the standard saying. And
>>>>glass does flow. No fairy tale. Actual
>>>>measurements show that glass standing vertically
>>>>for a long period is thicker at the bottom. Of
>>>>course it does take a long time.
>>>
>>>
>>>Please read this:
>>>http://tafkac.org/science/glass.flow/
>>>Just because your science teachers told you it does, doesn't mean they
>>>were right. The folks at alt.folklore.urban are damn good about
>>>tracking things down, and if you have something that isn't covered in
>>>their FAQs and is truly new information, they'd love to know about it.
>>>
>>
>>
>>I read it and wasn't impressed. Just typical
>>newsgroup bullshit and no scientific discussion or
>>evidence. I did like the part that says that the
>>greater thickness at the bottom of old panes of
>>glass was due to original variation in thickness
>>and that glaziers orient the thicker part to the
>>bottom. I thought of this as a possibility for
>>about 10 seconds before discarding it. First,
>>most glaziers probably didn't give a damn how the
>>glass was oriented and even if they did, they
>>couldn't tell the minute difference in thickness
>>without a micrometer on a consistent basis. That
>>would howlingly be funny to see a guy in the
>>1800's using a micrometer on glass panes before
>>glazing them.
>>
>>I suggest you use a microtome with glass knives to
>>find out for yourself and propose a different
>>reason for why a freshly broken edge will cut a
>>thinner slice.
>>
>>BTW, I doubt that many of my professors considered
>>or gave a damn about this burning issue. I'm sure
>>there is plenty of data out
>
>
Michael Daly wrote:
> On 4-Oct-2005, "George E. Cawthon" <[email protected]> wrote:
>
>
>>they couldn't tell the minute difference in thickness
>>without a micrometer on a consistent basis.
>
>
> Since they could see the difference by eye, why on earth would
> they bother with a micrometer?
>
> Mike
Your statement assumes a fact not in evidence.
The point is the glass worker couldn't see the
difference by eye on each pane and they couldn't
achieve the consistency of thicker at the bottom
by chance. It depends on what era of glass making
you are referring to. Some of the glass would
require very good measurement to tell the
difference in thickness, or are you saying that
you can just look at a pane of glass and tell that
one end is 0.001 inch thicker than the other? And
some rolled glass has so many waves and bubbles,
one couldn't decide which end was thicker.
"Mark Morin" <[email protected]> wrote:
>I guess I was spoiled with my old 2' x 3' glass. I could put 6 quarter
>sheets on it for sharpening chisels. Is was also big enough to put belt
>sander strips on it for plane soles. I considered MDF but I use 3M spray
>adhesive and it comes off nicely when changing papers (maybe Formica-type
>top would be better, which I haven't tried).
>
>I checked the granite -- price goes up quickly based on size and really
>quickly based on shipping.
>
>I'm going to try another piece of glass before going the granite route.
I've got a monster 4' x 3' sheet mounted to 5/4 birch ply and stiffened
w/ steel. I don't bother pulling it out unless I'm lapping the sole of a
bench plane or a slick.
I've found the outfeed table of my jointer works really well.
--
Archangel - Jack of all trades, mastering some...
Archangel & RavenSky's personal pages:
http://www.REMhastenslowly.com/
remove the REM... (sleep is over rated)
Charles Spitzer wrote:
> "George E. Cawthon" <[email protected]> wrote in message
> news:[email protected]...
>
>>Charles Spitzer wrote:
>>
>>
>>>and of course, all those pieces of cast glass that the egyptians
>>>carelesslly just left lying around are simply puddles by now.
>>
>>An incredibly stupid comment, for a great number of reasons. Do you know
>>anything about Egyptian glass making?
>
>
> well, actually, yes. it also doesn't having anything to do with the making
> of the glass, since they are still making glass the same way as 5000 years
> ago. shovel the raw materials into an oven. heat. pour out.
You sure you want to stick with that statement?
>
>>>i don't know where you got the above ideas, but you might want to recheck
>>>them.
>>>
>>>
>>
>>I'm sure you don't because you are too lazy to read.
>
>
> haha. please provide some cites as to what you are talking about glass
> flowing. as has been pointed out by others, that's been debunked quite a
> while ago.
No. you prove it with scientific data. Thickness
of glass over time under controlled conditions.
When you find one, let me know.
>
> regards,
> charlie
> http://glassartists.org/chaniarts
>
>
>
Bruce Barnett wrote:
> "George E. Cawthon" <[email protected]> writes:
>
>
>>I read it and wasn't impressed. Just typical newsgroup bullshit and
>>no scientific discussion or evidence.
>
>
> There is also no evidence that glass DOES flow. Can you point out one
> example of glass changing over time? Corning Museum of Glass has this
> to say:
>
> http://www.cmog.org/index.asp?pageId=745
>
>
> Of course, if you have evidence, then send it to them.
> I'm sure they would appreciate it.
>
Very interesting, but as the author pointed out,
he is talking about stained glass in cathedrals.
I also note that he says that a researcher found
about half of the pieces of glass in windows were
thicker on the top. I already argued that a
worker couldn't possibly have determined the thick
end and consistently placed that end on the
bottom. It is interesting that other use the
thick on the bottom for proof of glass flow and
others argue it is thick because the worker placed
it that way. Guess both arguments are bullshit,
which is what I said.
You have to know what the thickness was at the
beginning of the period and the end of the period,
regardless of whether the top or the bottom is the
thickest. No one has provided that information.
I don't if the flow idea from cathedral windows is
valid or not, most likely invalid. That doesn't
mean that there isn't evidence in lime glass. But,
if it flows it certainly moves very slowly. Does
it flow with pressure?
I wonder if Brill ever examined the aging of
broken glass edges with an electron microscope?
BTW, someone questioned the validity of the
supercooled liquid idea and wanted an authority.
How about Linus Pauling? Good enough?
I'm finished. If you find something definitive
(valid scientific tests that have been repeated by
several scientist) let me know. BTW, experiments
using current measurement techniques should easily
prove whether glass (softer kinds) actually flow
over time. The rest is just blather. Brill's
arguments on viscosity are rather weak and
trivial. Why not just do the experiments and
provide the data on thickness over time.
Dave Hinz wrote:
> On Mon, 03 Oct 2005 18:57:36 GMT, George E. Cawthon <[email protected]> wrote:
>
>
>>Super cooled liquid is the standard saying. And
>>glass does flow. No fairy tale. Actual
>>measurements show that glass standing vertically
>>for a long period is thicker at the bottom. Of
>>course it does take a long time.
>
>
> Please read this:
> http://tafkac.org/science/glass.flow/
> Just because your science teachers told you it does, doesn't mean they
> were right. The folks at alt.folklore.urban are damn good about
> tracking things down, and if you have something that isn't covered in
> their FAQs and is truly new information, they'd love to know about it.
>
I read it and wasn't impressed. Just typical
newsgroup bullshit and no scientific discussion or
evidence. I did like the part that says that the
greater thickness at the bottom of old panes of
glass was due to original variation in thickness
and that glaziers orient the thicker part to the
bottom. I thought of this as a possibility for
about 10 seconds before discarding it. First,
most glaziers probably didn't give a damn how the
glass was oriented and even if they did, they
couldn't tell the minute difference in thickness
without a micrometer on a consistent basis. That
would howlingly be funny to see a guy in the
1800's using a micrometer on glass panes before
glazing them.
I suggest you use a microtome with glass knives to
find out for yourself and propose a different
reason for why a freshly broken edge will cut a
thinner slice.
BTW, I doubt that many of my professors considered
or gave a damn about this burning issue. I'm sure
there is plenty of data out
On Tue, 4 Oct 2005 23:30:50 -0700, "Mark Morin" <[email protected]>
wrote:
>Just to clarify, I measured it on my table saw top, my 8" jointer, and my
>workbench ... all of which have been checked for flatness. But the real
>indicator is that if the piece is flipped over, the bow likewise switches
>from facing top to facing bottom.
>
>-- Mark
>
>
>
any chance of gluing it flat to something stiffer and flatter than it
is?
On Tue, 4 Oct 2005 09:44:37 -0700, "Charles Spitzer"
<[email protected]> wrote:
>
>"Larry Jaques" <novalidaddress@di\/ersify.com> wrote in message
>news:[email protected]...
>> On Mon, 3 Oct 2005 10:27:16 -0700, with neither quill nor qualm,
>> "Charles Spitzer" <[email protected]> quickly quoth:
>>
>>>"Larry Jaques" <novalidaddress@di\/ersify.com> wrote in message
>>
>>>> Good question. Glass does move; some say it's a liquid. I scratched my
>>>> new utility door window while removing the label. 2 months later I
>>>> noticed that the scratch had healed; it shocked the hell out of me.
>>>
>>>amorphous solid.
>>>
>>>it doesn't heal.
>>
>> That's what I used to think, but the window in my door did. I finally
>> got some Oops! and removed the remainder of the label.
<clue 1> label adhesive and razorblade. can leave residue that very
much resembles a scratch. I've made the same mistake.
>> The scratch was
>> plainly there after all the adhesive, etc. were gone. Months later the
>> scratch wasn't there any more. <cue Twi Zo music here>
>>
>> Ohhhh, maybe someone came up to my house, broke in, replaced the
>> glass, and sneaked back out, locking the door behind them.
>>
>> Yeah, I suppose it could happen. What are the odds, C? ;)
>
>i'd probably, without looking at it whilst it was scratched, have to say it
>wasn't really a scratch but some other mark on it. i've got glass that i've
>scratched or scored over 20 years old. i hae some other glass that i took
>out of an antique window that must have been 75 years old. they haven't
>healed yet and i'm not holding my breath.
>
>>
>>>> Leave the glass on the table for a month and see if it has settled.
>>>> It may have been stored upright where it took a bow.
>>>
>>>it doesn't take a set. it's pretty bendy. i have some 3/4" that bends over
>>>a
>>>4' span. when i fuse it together to make a 1.5" thick piece, it doesn't
>>>bend
>>>very much over a short span, but does over a much longer one.
>>>
>>>if you want it to be flat, you have to put it on something that is flat
>>>already.
>>>
>> You'd think he'd have straightedged the table he layed it on, wouldn't
>> you, before determining that only the glass was curved?
>
>ass-u-me. no, i'd not expect that.
except that the OP specified the flatness of the surface the glass was
sitting on....
In article <tj%%e.42536$sx2.18390@fed1read02>,
Mark Morin <[email protected]> wrote:
>I bought a new 2'x3' x 3/8" piece of plate/float glass and its not flat.
>Over the 3' there is a gap of .02" checking with a good straightedge. My No
>7 plane actually rocks on the glass. The underlying surface is flat. I've
>read that all plate glass is now the same as float so I don't think I bought
>the wrong type.
>
>I previously had (and cracked) a 1/4" thick piece that didn't vary by more
>than .003".
>
>What is a normal tolerance? Does thicker glass have greater tolerance for
>error?
>
>-- Mark
>
>
Modern float glass isn't designed with a "flatness" tolerance per se, the
flatness is really just a result of the way it is manufactured. For window
glass the .02 discrepancy would certainly be acceptable. :)
If you're on good terms with the glass shop maybe the will let you swap it
for another piece. Bring you straight edge with you this time. Or, you
could buy a granite surface plate, the ARE manufactured to a specified
tolerance.
--
[email protected]
SDF Public Access UNIX System - http://sdf.lonestar.org
"Larry Jaques" <novalidaddress@di\/ersify.com> wrote in message
news:[email protected]...
> On Sun, 2 Oct 2005 17:54:37 -0700, with neither quill nor qualm, "Mark
> Morin" <[email protected]> quickly quoth:
>
>>I bought a new 2'x3' x 3/8" piece of plate/float glass and its not flat.
>>Over the 3' there is a gap of .02" checking with a good straightedge. My
>>No
>>7 plane actually rocks on the glass. The underlying surface is flat.
>>I've
>>read that all plate glass is now the same as float so I don't think I
>>bought
>>the wrong type.
>
> So use a piece of MDF, or your kitchen countertop, fer Crikey's sake.
>
>
>>I previously had (and cracked) a 1/4" thick piece that didn't vary by more
>>than .003".
>>
>>What is a normal tolerance? Does thicker glass have greater tolerance for
>>error?
>
> Good question. Glass does move; some say it's a liquid. I scratched my
> new utility door window while removing the label. 2 months later I
> noticed that the scratch had healed; it shocked the hell out of me.
amorphous solid.
it doesn't heal.
> Leave the glass on the table for a month and see if it has settled.
> It may have been stored upright where it took a bow.
it doesn't take a set. it's pretty bendy. i have some 3/4" that bends over a
4' span. when i fuse it together to make a 1.5" thick piece, it doesn't bend
very much over a short span, but does over a much longer one.
if you want it to be flat, you have to put it on something that is flat
already.
regards,
charlie
http://glassartists.org/chaniarts
"George E. Cawthon" <[email protected]> wrote in message
news:[email protected]...
> Toller wrote:
>>>Good question. Glass does move; some say it's a liquid.
>>
>>
>> Thats an old wive's tale. Glass is amorphous, but certainly not liquid.
>>
>>
>>>I scratched my
>>>new utility door window while removing the label. 2 months later I
>>>noticed that the scratch had healed; it shocked the hell out of me.
>>>
>>
>> I think you just looked in the wrong place.
>> I scratched a microscope lens 35 years ago. It is still scratched
>> exactly as it was then.
>
> Super cooled liquid is the standard saying. And glass does flow. No
> fairy tale. Actual measurements show that glass standing vertically for a
> long period is thicker at the bottom. Of course it does take a long time.
and of course, all those pieces of cast glass that the egyptians carelesslly
just left lying around are simply puddles by now.
> Glass does heal. Anybody that works around glass or just uses his
> observation powers knows that freshly broken glass has much sharper edges
> than broken glass edges that have been around for a time. If that isn't
> enough for you, anyone that uses a microtome (you know one of those things
> that cuts very thin slices for microscope slides) and uses glass for the
> cutter, knows that you use a freshly broken surface. Let it sit around
> for a while and you won't be able to cut as thin slices as freshly broken,
> note we are talking about slices less than 10 microns thick. Of course,
> you could even more simply use a microscope to examine broken glass edges.
> The type of glass also makes a very big difference to how fast it heals.
>
> Nonetheless, I don't believe the healed glass scratch in a window. Two
> months is too short a time to possibly observe that; 20-30 years for a
> very, very light nearly invisible scratch on window glass, maybe but more
> likely 100+ years. Probably was a scratch in the dirt on the glass or
> maybe just a thin cobweb.
>
> I've been waiting for 5 years for a scratch in a new window to heal. Har.
> Har. Not really, the house will be torn down long before that glass
> heals.
>
> As for the microscope lens, it might be very hard, heck it could be
> crystalline quartz, but not likely. In addition, the scratch would have to
> be on a vertically oriented plane to heal in any observable way.
i don't know where you got the above ideas, but you might want to recheck
them.
Dave Hinz <[email protected]> writes:
> Please read this:
> http://tafkac.org/science/glass.flow/
As I recall, FWW mentioned this myth long ago. The story goes is that
old glass is thicker at the bottom because they made it using a
technqiue that didn't make flat glass. Something about slab cooled,
and one end being cooler than the other.
And when they placed it in windows, they put the thicker edge down
just like they did with shingles. So the thicker end is due to habit.
But you are in good company, George. Marylin vos Savant (smartest
person in the world) also got it wrong in her column.
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"George E. Cawthon" <[email protected]> writes:
> I read it and wasn't impressed. Just typical newsgroup bullshit and
> no scientific discussion or evidence.
There is also no evidence that glass DOES flow. Can you point out one
example of glass changing over time? Corning Museum of Glass has this
to say:
http://www.cmog.org/index.asp?pageId=745
Of course, if you have evidence, then send it to them.
I'm sure they would appreciate it.
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"George E. Cawthon" <[email protected]> wrote in message
news:[email protected]...
> Charles Spitzer wrote:
>
>> and of course, all those pieces of cast glass that the egyptians
>> carelesslly just left lying around are simply puddles by now.
>
> An incredibly stupid comment, for a great number of reasons. Do you know
> anything about Egyptian glass making?
well, actually, yes. it also doesn't having anything to do with the making
of the glass, since they are still making glass the same way as 5000 years
ago. shovel the raw materials into an oven. heat. pour out.
>>
>> i don't know where you got the above ideas, but you might want to recheck
>> them.
>>
>>
> I'm sure you don't because you are too lazy to read.
haha. please provide some cites as to what you are talking about glass
flowing. as has been pointed out by others, that's been debunked quite a
while ago.
regards,
charlie
http://glassartists.org/chaniarts
"Larry Jaques" <novalidaddress@di\/ersify.com> wrote in message
news:[email protected]...
> On Mon, 3 Oct 2005 10:27:16 -0700, with neither quill nor qualm,
> "Charles Spitzer" <[email protected]> quickly quoth:
>
>>"Larry Jaques" <novalidaddress@di\/ersify.com> wrote in message
>
>>> Good question. Glass does move; some say it's a liquid. I scratched my
>>> new utility door window while removing the label. 2 months later I
>>> noticed that the scratch had healed; it shocked the hell out of me.
>>
>>amorphous solid.
>>
>>it doesn't heal.
>
> That's what I used to think, but the window in my door did. I finally
> got some Oops! and removed the remainder of the label. The scratch was
> plainly there after all the adhesive, etc. were gone. Months later the
> scratch wasn't there any more. <cue Twi Zo music here>
>
> Ohhhh, maybe someone came up to my house, broke in, replaced the
> glass, and sneaked back out, locking the door behind them.
>
> Yeah, I suppose it could happen. What are the odds, C? ;)
i'd probably, without looking at it whilst it was scratched, have to say it
wasn't really a scratch but some other mark on it. i've got glass that i've
scratched or scored over 20 years old. i hae some other glass that i took
out of an antique window that must have been 75 years old. they haven't
healed yet and i'm not holding my breath.
>
>>> Leave the glass on the table for a month and see if it has settled.
>>> It may have been stored upright where it took a bow.
>>
>>it doesn't take a set. it's pretty bendy. i have some 3/4" that bends over
>>a
>>4' span. when i fuse it together to make a 1.5" thick piece, it doesn't
>>bend
>>very much over a short span, but does over a much longer one.
>>
>>if you want it to be flat, you have to put it on something that is flat
>>already.
>>
> You'd think he'd have straightedged the table he layed it on, wouldn't
> you, before determining that only the glass was curved?
ass-u-me. no, i'd not expect that.
> --
> "Most Folks Are As Happy As They Make Up Their Minds To Be"
> -Abraham Lincoln
> -----------------------------------------------------------
> www.diversify.com - Happy Website Development
regards,
charlie
http://glassartists.org/chaniarts
"George E. Cawthon" <[email protected]> writes:
> I already argued that a worker couldn't possibly
> have determined the thick end and consistently placed that end on the
> bottom. It is interesting that other use the thick on the bottom for
> proof of glass flow and others argue it is thick because the worker
> placed it that way. Guess both arguments are bullshit, which is what
> I said.
It doesn't claim that glass is always laid that way. Just that it's
done SOME times, and I'm sure the urban myth wasn't started by someone
using a micrometer. Since there is no evidence of glass flowing, that
theory explains why some houses DO have "thicker at the bottom" glass
better than any other theory.
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max <[email protected]> writes:
> Glass is amorphous. The quick explanation is that is not a solid or a
> liquid.
Heavy Sigh. Please READ the article before you jump in.
This is another reason why top-posting is bad.
[snip]
>>> http://tafkac.org/science/glass.flow/
This should have been at the top of the response, because it provides
facts that contradict your statement.
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"Mark Morin" <[email protected]> wrote in message
news:AoK0f.224$UF4.5@fed1read02...
> "Larry Jaques" <novalidaddress@di\/ersify.com> wrote in message
> news:[email protected]...
>> On Mon, 3 Oct 2005 10:27:16 -0700, with neither quill nor qualm,
>> "Charles Spitzer" <[email protected]> quickly quoth:
>>
>>>"Larry Jaques" <novalidaddress@di\/ersify.com> wrote in message
>>>>if you want it to be flat, you have to put it on something that is flat
>>>>already.
>>>>
>>> You'd think he'd have straightedged the table he layed it on, wouldn't
>>> you, before determining that only the glass was curved?
>>
>> ass-u-me. no, i'd not expect that.
>
> From my original message ... "The underlying surface is flat".
>
> Thanks for the vote of confidence. Is this where I say, "you'd think they
> read the original post."
> and you reply, "Ass-me. No, I'd not expect that" :)
>
> Just to clarify, I measured it on my table saw top, my 8" jointer, and my
> workbench ... all of which have been checked for flatness. But the real
> indicator is that if the piece is flipped over, the bow likewise switches
> from facing top to facing bottom.
>
> -- Mark
there you go again, bringing in facts to ruin a good argument.
could it be tempered? tempered glass almost always has a very slight bow in
it.
My suggestion, look at Grizzly at the granite flats/plates, grade B
flatness and very thick, works like a charm here for scary sharp,
and I don't have to worry about how much pressure I apply while
sharpening - I think I paid around $20 for a 9x13 one from Grizzly
John
On Sun, 2 Oct 2005 17:54:37 -0700, "Mark Morin" <[email protected]>
wrote:
>I bought a new 2'x3' x 3/8" piece of plate/float glass and its not flat.
>Over the 3' there is a gap of .02" checking with a good straightedge. My No
>7 plane actually rocks on the glass. The underlying surface is flat. I've
>read that all plate glass is now the same as float so I don't think I bought
>the wrong type.
>
>I previously had (and cracked) a 1/4" thick piece that didn't vary by more
>than .003".
>
>What is a normal tolerance? Does thicker glass have greater tolerance for
>error?
>
>-- Mark
>
On Tue, 4 Oct 2005 09:44:37 -0700, with neither quill nor qualm,
"Charles Spitzer" <[email protected]> quickly quoth:
>"Larry Jaques" <novalidaddress@di\/ersify.com> wrote in message
>> That's what I used to think, but the window in my door did. I finally
>> got some Oops! and removed the remainder of the label. The scratch was
>> plainly there after all the adhesive, etc. were gone. Months later the
>> scratch wasn't there any more. <cue Twi Zo music here>
>i'd probably, without looking at it whilst it was scratched, have to say it
>wasn't really a scratch but some other mark on it. i've got glass that i've
>scratched or scored over 20 years old. i hae some other glass that i took
>out of an antique window that must have been 75 years old. they haven't
>healed yet and i'm not holding my breath.
As I said, I thoroughly cleaned the thing, then inspected it
carefully. Sure enough, it was a scratch. Of that I have absolutely
no doubt. It caught my fingernail and had a gritty sound when it did.
But it was gone at a later date. I'm convinced that some formulations
of glass do heal. Oh, I also looked for some sort of coating on the
glass and found none. It "ticked" when I tapped it with my fingernail.
I'm still tickled that it fixed itself. BTW, I've been sober for 20
years straight now, so I wasn't liquidly mistaken. ;)
--------------------------------------------------------
Murphy was an Optimist
----------------------------
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Isn't there a rec.glasworking?
--
Larry Wasserman Baltimore, Maryland
[email protected]
On Tue, 04 Oct 2005 20:01:03 -0400, Kenneth
<[email protected]> wrote:
>On Mon, 03 Oct 2005 18:57:36 GMT, "George E. Cawthon"
><[email protected]> wrote:
>
>>Super cooled liquid is the standard saying. And
>>glass does flow. No fairy tale. Actual
>>measurements show that glass standing vertically
>>for a long period is thicker at the bottom. Of
>>course it does take a long time.
>
>Howdy,
>
>You might want to read:
>
>http://math.ucr.edu/home/baez/physics/General/Glass/glass.html
>
>Among other things, it indicates that the "flow" concept has
>not been demonstrated.
>
>All the best,
Ooops,
I responded before reading further in the thread.
Others have offered similar citations.
All the best,
--
Kenneth
If you email... Please remove the "SPAMLESS."
On 4-Oct-2005, "George E. Cawthon" <[email protected]> wrote:
> they couldn't tell the minute difference in thickness
> without a micrometer on a consistent basis.
Since they could see the difference by eye, why on earth would
they bother with a micrometer?
Mike
On Mon, 3 Oct 2005 10:27:16 -0700, with neither quill nor qualm,
"Charles Spitzer" <[email protected]> quickly quoth:
>"Larry Jaques" <novalidaddress@di\/ersify.com> wrote in message
>> Good question. Glass does move; some say it's a liquid. I scratched my
>> new utility door window while removing the label. 2 months later I
>> noticed that the scratch had healed; it shocked the hell out of me.
>
>amorphous solid.
>
>it doesn't heal.
That's what I used to think, but the window in my door did. I finally
got some Oops! and removed the remainder of the label. The scratch was
plainly there after all the adhesive, etc. were gone. Months later the
scratch wasn't there any more. <cue Twi Zo music here>
Ohhhh, maybe someone came up to my house, broke in, replaced the
glass, and sneaked back out, locking the door behind them.
Yeah, I suppose it could happen. What are the odds, C? ;)
>> Leave the glass on the table for a month and see if it has settled.
>> It may have been stored upright where it took a bow.
>
>it doesn't take a set. it's pretty bendy. i have some 3/4" that bends over a
>4' span. when i fuse it together to make a 1.5" thick piece, it doesn't bend
>very much over a short span, but does over a much longer one.
>
>if you want it to be flat, you have to put it on something that is flat
>already.
>
You'd think he'd have straightedged the table he layed it on, wouldn't
you, before determining that only the glass was curved?
--
"Most Folks Are As Happy As They Make Up Their Minds To Be"
-Abraham Lincoln
-----------------------------------------------------------
www.diversify.com - Happy Website Development
"Charles Spitzer" <[email protected]> writes:
[...]
> it doesn't take a set. it's pretty bendy. i have some 3/4" that bends over a
> 4' span. when i fuse it together to make a 1.5" thick piece, it doesn't bend
> very much over a short span, but does over a much longer one.
The rule of thumb for mirrors in telescopes is to make them only six
times wider than they are thick to prevent them from sagging under
their own weight.
For scary sharpening or waterstone flatening I use a ground and
polished concrete fake granite plate of the kind used in garden paths,
I cannot detect any deviation from flat with a straightedge and it was
cheap, about 3EUR for a 40cm times 40cm size.
--
Dr. Juergen Hannappel http://lisa2.physik.uni-bonn.de/~hannappe
mailto:[email protected] Phone: +49 228 73 2447 FAX ... 7869
Physikalisches Institut der Uni Bonn Nussallee 12, D-53115 Bonn, Germany
CERN: Phone: +412276 76461 Fax: ..77930 Bat. 892-R-A13 CH-1211 Geneve 23
On 4-Oct-2005, "George E. Cawthon" <[email protected]> wrote:
> It depends on what era of glass making
> you are referring to.
If you're talking about the oldest examples of glass then
you most certainly can see the difference in thickness by eye.
These are also the examples where studies have shown that a
very significant majority are placed with the thick end down.
Your objections are not based on fact but on your refusal to
accept the facts.
Mike