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Glass grinders.



 
 
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  #1  
Old August 16th 08, 05:35 AM posted to rec.crafts.glass
Bill Browne
external usenet poster
 
Posts: 7
Default Glass grinders.

I work in etched glass, not stained. But I like to work with odd shapes, so
I've considered a glass grinder, and I have a few questions.

I'm curious as to how badly the edge is chipped after its been ground. I
know the stained glass crowd puts came or foil around the edge, so it isn't
an issue. But for me, it might be. Can someone send me a close-up pic of
the edge of a piece of glass after it's been ground so I can see the finish?
Also, it looks to me that most grinding heads are 3/4 to an inch tall.
Would they'd work on 3/8" or 1/2" glass? Seems like it'd be OK, but wonder
if anyone out there has had experience with this?

Thanks.

Bill


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  #2  
Old August 16th 08, 07:59 AM posted to rec.crafts.glass
Lauri Levanto
external usenet poster
 
Posts: 55
Default Glass grinders.

Bill Browne wrote:
I work in etched glass, not stained. But I like to work with odd shapes, so
I've considered a glass grinder, and I have a few questions.

I'm curious as to how badly the edge is chipped after its been ground. I
know the stained glass crowd puts came or foil around the edge, so it isn't
an issue. But for me, it might be. Can someone send me a close-up pic of
the edge of a piece of glass after it's been ground so I can see the finish?
Also, it looks to me that most grinding heads are 3/4 to an inch tall.
Would they'd work on 3/8" or 1/2" glass? Seems like it'd be OK, but wonder
if anyone out there has had experience with this?

Thanks.

Bill


I work with fused glass, so I have the same grinding question.
The normal coarse head leaves a very dull scraped durfsce. You can buy a
fine head to smooth after that.
Diamond hand pads are good for finish. You need a series, like
220, 400 and 600 grits. After that you have a surfade like sandblasted.
further finsih requires polishing.
HAve you consider fire polishing?

-lauri
  #3  
Old August 16th 08, 08:24 AM posted to rec.crafts.glass
Adrian
external usenet poster
 
Posts: 48
Default Glass grinders.

Hi Bill

Bill Browne wrote:
I work in etched glass, not stained. But I like to work with odd shapes, so
I've considered a glass grinder, and I have a few questions.

I'm curious as to how badly the edge is chipped after its been ground.


Simple answer is 'it varies' g - seems to depend on the type of glass.
Some glass will chip at the edges, some doesn't. Plain, clear,
machine-made float glass is usually OK - the more 'fancy' the glass gets
the more liable it seems to be to get chipped...

I
know the stained glass crowd puts came or foil around the edge, so it isn't
an issue. But for me, it might be. Can someone send me a close-up pic of
the edge of a piece of glass after it's been ground so I can see the finish?


My experience is that, wherever possible, it's best to cut rather than
grind (quicker!). However, when I'm doing foiled work, I always run
round the edge of the cut glass with the grinder, just to take off any
sharp edges that would otherwise damage the foil (or me!)

There are different grit grades of grinding head available - I tend to
use 100 grade most of the time - and usually a 3/4" head. If you want to
take the time, then you can use heads with finer grit - I sometimes use
a 600-grade head, but not very often.

I do quite a lot of work with mirrored glass - and have just bought a
specific mirror-grinding head - which grinds both top and bottom surface
of the glass at the same time. I'm still experimenting with it - but it
does seem to reduce the problem of chipping the mirror coating off the
glass - and leaves a reasonable semi-rounded edge on the glass.
Aanraku do them. I'd imagine that, using a combination of the
mirror-grinder head and a conventional coarse head you could create an
acceptable finish on the edges of your etched glass work..

The mirror-grinder head does tend to 'grab' the glass and try to throw
it across the workshop - so practice on some scrap first! g

Also, it looks to me that most grinding heads are 3/4 to an inch tall.
Would they'd work on 3/8" or 1/2" glass? Seems like it'd be OK, but wonder
if anyone out there has had experience with this?


The 'standard' grinder head can be moved & locked up & down the grinder
spindle - so you can start out with the head only just showing above the
grinder table, and then, once that 3mm strip of diamonds has gone dull,
you can re-set the position so a fresh set of diamonds is exposed - so
you can get mugh longer life from a single grinder head...

If you want some photos then I'll send you some after the weekend (busy
selling at the open-air markets this weekend - weather permitting.

Hope this helps
Adrian
www.inspired-glass.com
  #4  
Old August 16th 08, 03:56 PM posted to rec.crafts.glass
[email protected]
external usenet poster
 
Posts: 320
Default Glass grinders.

On Aug 15, 9:35*pm, "Bill Browne" wrote:
I work in etched glass, not stained. *But I like to work with odd shapes, so
I've considered a glass grinder, and I have a few questions.

I'm curious as to how badly the edge is chipped after its been ground. *I
know the stained glass crowd puts came or foil around the edge, so it isn't
an issue. *But for me, it might be. *Can someone send me a close-up pic of
the edge of a piece of glass after it's been ground so I can see the finish?
Also, it looks to me that most grinding heads are 3/4 to an inch tall.
Would they'd work on 3/8" or 1/2" glass? *Seems like it'd be OK, but wonder
if anyone out there has had experience with this?

Thanks.

Bill


The grinder head is 3/4" tall to allow you to lift or lower it to have
more grinding surface. Start by using one edge then at it wears down,
reposition the head to provide a fresh surface.

You didn't say if you've been etching with acid of sandblasting. I'll
assume you're either sandblasting or have some familiarity with how
sandblasting etches glass. It's a direct comparison. A grinder head
will not produce any smoother finish then sandblasting. A 100 grit
grind will leave the same frosted slightly rough finish as a 100 grit
sandblast. A 600 grit grind will leave the same surface as 600 grit
sandblast. If you want a perfectly smooth finish, you won't get it
with a grinder any more then with sandblasting.

Dennis Brady

DeBrady Glassworks - http://www.debrady.com
Glass Campus - http://www.glasscampus.com
Victorian Art Glass - http://www.vicartglass.com
  #5  
Old August 17th 08, 10:19 PM posted to rec.crafts.glass
Bill Browne
external usenet poster
 
Posts: 7
Default Glass grinders--thanks to all.

Thanks to all who responded to my post. They were quite helpful.

I am using a sandblaster. And I'm not really looking for a purfectly
polished edge. In fact, I've used the blaster to finish the edge of the
glass a time or two. Seems like a grinder with a couple of different heads
might do the trick.

Lauri brought up fire polishing. I'm wondering how much fire are we talking
about. I'm guessing more than my propane torch can supply.

Anyway, thanks again.

"Bill Browne" wrote in message
...
I work in etched glass, not stained. But I like to work with odd shapes,
so I've considered a glass grinder, and I have a few questions.

I'm curious as to how badly the edge is chipped after its been ground. I
know the stained glass crowd puts came or foil around the edge, so it
isn't an issue. But for me, it might be. Can someone send me a close-up
pic of the edge of a piece of glass after it's been ground so I can see
the finish? Also, it looks to me that most grinding heads are 3/4 to an
inch tall. Would they'd work on 3/8" or 1/2" glass? Seems like it'd be
OK, but wonder if anyone out there has had experience with this?

Thanks.

Bill



  #6  
Old August 18th 08, 12:38 AM posted to rec.crafts.glass
[email protected]
external usenet poster
 
Posts: 320
Default Glass grinders--thanks to all.

On Aug 17, 3:12Â*pm, Steve Ackman
wrote:
In , on Sun, 17
Aug 2008 21:19:17 GMT, Bill Browne, wrote:

Lauri brought up fire polishing. Â*I'm wondering how much fire are we talking
about. Â*I'm guessing more than my propane torch can supply.


Â* A point source of heat like a torch will break your
glass. Â*In order to fire polish, you need the entire
piece of to be at least to the strain point, and
preferably at or above the anneal point (~950-1000°F).
Then you can apply a torch to the edge to fire polish
without worrying about thermal shock, ΔT's, or internal
stresses.
Â* IOW, fire polishing is generally done in a kiln.
For your application, I'd think you'd want to fire
polish before doing any carving/etching.

--
☯☯


"Fire polishing" is a term used to refer to a method of producing a
smooth edge by heating the glass in a kiln to a temperature high
enough for the glass edge to soften and smooth out. Clear float glass
would require heating to 1350F and holding at that temperature for 6
to 10 minutes (depending on how smooth it was ground before going into
the kiln).

As was mentioned, it is essential the glass be heated uniformly. It
it isn't heated uniformly, it will crack. Can't do it with a torch
unless the torch is big enough to fan flame over the entire glass
surface.
  #7  
Old August 18th 08, 05:13 AM posted to rec.crafts.glass
Bill Browne
external usenet poster
 
Posts: 7
Default Glass grinders--thanks to all.

Understood. And since I won't be buying a kiln anytime soon, I'll stick to
grinding.

Again, thanks to all.

wrote in message
...
On Aug 17, 3:12 pm, Steve Ackman
wrote:
In , on Sun, 17
Aug 2008 21:19:17 GMT, Bill Browne, wrote:

Lauri brought up fire polishing. I'm wondering how much fire are we
talking
about. I'm guessing more than my propane torch can supply.


A point source of heat like a torch will break your
glass. In order to fire polish, you need the entire
piece of to be at least to the strain point, and
preferably at or above the anneal point (~950-1000°F).
Then you can apply a torch to the edge to fire polish
without worrying about thermal shock, ?T's, or internal
stresses.
IOW, fire polishing is generally done in a kiln.
For your application, I'd think you'd want to fire
polish before doing any carving/etching.

--
??


"Fire polishing" is a term used to refer to a method of producing a
smooth edge by heating the glass in a kiln to a temperature high
enough for the glass edge to soften and smooth out. Clear float glass
would require heating to 1350F and holding at that temperature for 6
to 10 minutes (depending on how smooth it was ground before going into
the kiln).

As was mentioned, it is essential the glass be heated uniformly. It
it isn't heated uniformly, it will crack. Can't do it with a torch
unless the torch is big enough to fan flame over the entire glass
surface.


  #8  
Old August 18th 08, 05:56 AM posted to rec.crafts.glass
Lauri Levanto
external usenet poster
 
Posts: 55
Default Glass grinders--thanks to all.

Bill Browne wrote:


Lauri brought up fire polishing. I'm wondering how much fire are we talking
about. I'm guessing more than my propane torch can supply.

Anyway, thanks again.




Firepolishing needs some 740-760 C.
With a propane torch that is enough to thermal shock the glass and
polsih away the sandblasting.

What I had in mind was to heat the blank *in kiln* to firepolish the
edges, then you can sandblast the picture.

-lauri
  #9  
Old August 19th 08, 10:28 PM posted to rec.crafts.glass
Kris Krieger
external usenet poster
 
Posts: 43
Default Glass grinders.

Adrian wrote in
:

Hi Bill

Bill Browne wrote:
I work in etched glass, not stained. But I like to work with odd
shapes, so I've considered a glass grinder, and I have a few questions.

I'm curious as to how badly the edge is chipped after its been ground.


Simple answer is 'it varies' g - seems to depend on the type of glass.
Some glass will chip at the edges, some doesn't. Plain, clear,
machine-made float glass is usually OK - the more 'fancy' the glass gets
the more liable it seems to be to get chipped...


What I've found in grinding clear textured glass and colroed glass up to
3/8" is taht you have to be very sure to keep the glass flat on the grinder
table, and apply a smooth, even pressure while grinding.


I
know the stained glass crowd puts came or foil around the edge, so it
isn't an issue. But for me, it might be. Can someone send me a
close-up pic of the edge of a piece of glass after it's been ground so
I can see the finish?


My experience is that, wherever possible, it's best to cut rather than
grind (quicker!). However, when I'm doing foiled work, I always run
round the edge of the cut glass with the grinder, just to take off any
sharp edges that would otherwise damage the foil (or me!)


I'm not a pro, but from all I've heard and read, the reason for the grinding
is to provide "tooth" to improve the adhesion of teh sticky side of the foil
becasue, if the glass is smooth, you lose structural integrity - is that
incorrect?

I took a kiln-worked glass course and the instructor used the diamond-sponges
to finish edges. The grinder is good for removing larger amounts, but yeah,
you're right, the OP should cut as close as possible to the intended outline
of the item, since that will reduce wear on the grinder head (since it won't
have to be used as much).

[snip]

HTH!

- Kris


  #10  
Old August 19th 08, 11:37 PM posted to rec.crafts.glass
[email protected]
external usenet poster
 
Posts: 320
Default Glass grinders.

On Aug 19, 2:28*pm, Kris Krieger wrote:
Adrian wrote :

Hi Bill


Bill Browne wrote:
I work in etched glass, not stained. *But I like to work with odd
shapes, so I've considered a glass grinder, and I have a few questions..


I'm curious as to how badly the edge is chipped after its been ground.


Simple answer is 'it varies' g - seems to depend on the type of glass..
Some glass will chip at the edges, some doesn't. Plain, clear,
machine-made float glass is usually OK - the more 'fancy' the glass gets
the more liable it seems to be to get chipped...


What I've found in grinding clear textured glass and colroed glass up to
3/8" is taht you have to be very sure to keep the glass flat on the grinder
table, and apply a smooth, even pressure while grinding.

I
know the stained glass crowd puts came or foil around the edge, so it
isn't an issue. *But for me, it might be. *Can someone send me a
close-up pic of the edge of a piece of glass after it's been ground so
I can see the finish?


My experience is that, wherever possible, it's best to cut rather than
grind (quicker!). However, when I'm doing foiled work, I always run
round the edge of the cut glass with the grinder, just to take off any
sharp edges that would otherwise damage the foil (or me!)


I'm not a pro, but from all I've heard and read, the reason for the grinding
is to provide "tooth" to improve the adhesion of teh sticky side of the foil
becasue, if the glass is smooth, you lose structural integrity - is that
incorrect?

I took a kiln-worked glass course and the instructor used the diamond-sponges
to finish edges. *The grinder is good for removing larger amounts, but yeah,
you're right, the OP should cut as close as possible to the intended outline
of the item, since that will reduce wear on the grinder head (since it won't
have to be used as much).

[snip]

HTH!

- Kris


Grinding the edge will remove any overhanging shards but does nothing
to help the foil stick. It sticks better to a smooth surface then a
ground one. Foil has no structural integrity. The glue is there just
to hold the foil in place until the solder is applied. Foil is only
to provide a platform for the solder.

If you have access to a wet belt sander, it'll provide a substantially
superior edge then a grinder.
 




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