Cutting small piece of (tempered) glass precisely?

[blueman]

I need to trim the glass diffuser for an LED light to fit inside a
cabinet. I need to do it quite precisely and I have not been very good
in the past using a standard glass cutter (either I have trouble
scratching a precise straight line or it doesn't break smoothly).

The piece of glass is about 1/8 thick and 1.5 inches deep so I don't
need to cut much. I only need to trim off about 1/4 inch (which makes
using a hand-held glass cutter even harder). I'm pretty sure the glass
is tempered.

Would a dremel with a diamond-coated rotary disc do a good job of making
a smooth cut?
(for example
http://insidetrackclub.harborfreight.com/5-piece-diamond-mini-cutting-discs-31501.html
)

Since the discs are so thin, I would hope to be able to make a precise cut by
following the line and sneaking up on it as needed..

Would this work?
Any other suggestions?
`
Note: I tried using an angle grinder (with a metal grinding blade) and also a
belt sander - but both of those approaches ended up more melting the
glass (it got "yellow" hot) which caused it to crumble and ooze.

[Larry Jaques]

On Sun, 08 Jan 2012 17:55:09 -0500, blueman <NOS...@nospam.com> wrote:

>I need to trim the glass diffuser for an LED light to fit inside a
>cabinet. I need to do it quite precisely and I have not been very good
>in the past using a standard glass cutter (either I have trouble
>scratching a precise straight line or it doesn't break smoothly).
>
>The piece of glass is about 1/8 thick and 1.5 inches deep so I don't
>need to cut much. I only need to trim off about 1/4 inch (which makes
>using a hand-held glass cutter even harder). I'm pretty sure the glass
>is tempered.

Tempered glass will shatter when you try to cut it with a glass
cutter. DO NOT TRY THIS.

>Would a dremel with a diamond-coated rotary disc do a good job of making
>a smooth cut?
>(for example
>http://insidetrackclub.harborfreight.com/5-piece-diamond-mini-cutting-discs-31501.html
>)
>
>Since the discs are so thin, I would hope to be able to make a precise cut by
>following the line and sneaking up on it as needed..

Might work, but once you break through, they tend to vibrate, probably
enough to shatter the glass.

>Would this work?
>Any other suggestions?

Add a false bottom to the cabinet with a 1/4" deep rabbeted hole.

>Note: I tried using an angle grinder (with a metal grinding blade) and also a
>belt sander - but both of those approaches ended up more melting the
>glass (it got "yellow" hot) which caused it to crumble and ooze.

I think the belt sander sounds the best. Use a wet rag to cool the
glass before it turns any kind of red. This will definitely take
awhile. Be patient.

Glass dust is really nastyass stuff. I hope you're using goggles, a
respirator with P100 filters, and a shop vac or dust collector.

How about a pic of the glass part? Are you talking about a glass in a
washer shape or a tube shape?

--
Another belief of mine: that everyone else my age is an adult,
whereas I am merely in disguise.
-- Margaret Atwood

[Ed Pawlowski]

On Sun, 08 Jan 2012 17:55:09 -0500, blueman <NOS...@nospam.com> wrote:

>I need to trim the glass diffuser for an LED light to fit inside a
>cabinet. I need to do it quite precisely and I have not been very good
>in the past using a standard glass cutter (either I have trouble
>scratching a precise straight line or it doesn't break smoothly).
>

Doubt you'll have much luck, but take measurements first so you can
get a proper replacement.


http://www.onedayglass.com/patterns.php
Cutting Tempered Glass

We are often asked if we can cut glass that has already been tempered.
Unfortunately, the answer to this question is no. All fabrication is
done prior to tempering. That means we cut your piece to your exact
specifications, drill and edge, and make all necessary customizations.
Then we heat treat it in our unique vertical tempering furnace* and
ship it to you.


Cutting Tempered Glass
1


Clean your tempered glass thoroughly and dry completely.

2


Place your tempered glass into a craft oven and set the temperature to
900 degrees F. Once the glass has reached this temperature, turn the
oven off and allow the oven and the glass to cool for at least eight
hours before removing the glass from the oven. This process is known
as annealing, and it removes stress from the glass. The glass is no
longer tempered.



Read more: How to Cut Tempered Glass | eHow.com
http://www.ehow.com/how_4678952_cut-tempered-glass.html#ixzz1iuprcxBv
It has to be annealed first.

[Father Haskell]

On Jan 8, 5:55 pm, blueman <NOS...@nospam.com> wrote:
> I need to trim the glass diffuser for an LED light to fit inside a
> cabinet. I need to do it quite precisely and I have not been very good
> in the past using a standard glass cutter (either I have trouble
> scratching a precise straight line or it doesn't break smoothly).
>
> The piece of glass is about 1/8 thick and 1.5 inches deep so I don't
> need to cut much. I only need to trim off about 1/4 inch (which makes
> using a hand-held glass cutter even harder). I'm pretty sure the glass
> is tempered.
>
> Would a dremel with a diamond-coated rotary disc do a good job of making
> a smooth cut?

> (for examplehttp://insidetrackclub.harborfreight.com/5-piece-diamond-mini-cutting...

> )
>
> Since the discs are so thin, I would hope to be able to make a precise cut by
> following the line and sneaking up on it as needed..
>
> Would this work?
> Any other suggestions?
> `
> Note: I tried using an angle grinder (with a metal grinding blade) and also a
> belt sander - but both of those approaches ended up more melting the
> glass (it got "yellow" hot) which caused it to crumble and ooze.

Tempered glass is made by spraying the hot sheet on
both faces with water, which rapidly cools them and
puts them under tension. It's this tension that gives
the glass its strength. As soon as you weaken one
side by cutting it, you release tension on the opposite
side, and it shatters. Annealing solves that problem,
but I have a feeling it's not practical for your project.

[chaniarts]

On 1/8/2012 6:47 PM, Father Haskell wrote:
> On Jan 8, 5:55 pm, blueman<NOS...@nospam.com> wrote:
>> I need to trim the glass diffuser for an LED light to fit inside a
>> cabinet. I need to do it quite precisely and I have not been very good
>> in the past using a standard glass cutter (either I have trouble
>> scratching a precise straight line or it doesn't break smoothly).
>>
>> The piece of glass is about 1/8 thick and 1.5 inches deep so I don't
>> need to cut much. I only need to trim off about 1/4 inch (which makes
>> using a hand-held glass cutter even harder). I'm pretty sure the glass
>> is tempered.
>>
>> Would a dremel with a diamond-coated rotary disc do a good job of making
>> a smooth cut?
>> (for examplehttp://insidetrackclub.harborfreight.com/5-piece-diamond-mini-cutting...
>> )
>>
>> Since the discs are so thin, I would hope to be able to make a precise cut by
>> following the line and sneaking up on it as needed..
>>
>> Would this work?
>> Any other suggestions?
>> `
>> Note: I tried using an angle grinder (with a metal grinding blade) and also a
>> belt sander - but both of those approaches ended up more melting the
>> glass (it got "yellow" hot) which caused it to crumble and ooze.
>
> Tempered glass is made by spraying the hot sheet on
> both faces with water, which rapidly cools them and

air.

> puts them under tension. It's this tension that gives
> the glass its strength. As soon as you weaken one
> side by cutting it, you release tension on the opposite
> side, and it shatters. Annealing solves that problem,
> but I have a feeling it's not practical for your project.
>

its pretty hard to trim off a very small piece of glass without normal
glass tools. take it to a stained glass place and they'd probably do it
for free. it is usually done with a water cooled diamond glass bit, but
can be done with SiC belts on a belt sander that you spray with a bit of
water. if the glass is glowing, then it's WAY too hot and spraying water
on it will probably shatter it.

[Bruce]

On Sun, 8 Jan 2012 15:55:09 -0700, blueman wrote
(in article <m2ehv94...@consult.pretender>):

> I need to trim the glass diffuser for an LED light to fit inside a
> cabinet. I need to do it quite precisely and I have not been very good
> in the past using a standard glass cutter (either I have trouble
> scratching a precise straight line or it doesn't break smoothly).
>
> The piece of glass is about 1/8 thick and 1.5 inches deep so I don't
> need to cut much. I only need to trim off about 1/4 inch (which makes
> using a hand-held glass cutter even harder). I'm pretty sure the glass
> is tempered.
>
> Would a dremel with a diamond-coated rotary disc do a good job of making
> a smooth cut?
> (for example
>
http://insidetrackclub.harborfreight.com/5-piece-diamond-mini-cutting-discs-
31
> 501.html
>>
>

> Since the discs are so thin, I would hope to be able to make a precise cut by
> following the line and sneaking up on it as needed..
>
> Would this work?
> Any other suggestions?
> `
> Note: I tried using an angle grinder (with a metal grinding blade) and also a
> belt sander - but both of those approaches ended up more melting the
> glass (it got "yellow" hot) which caused it to crumble and ooze.
>

I work a lot with LED lighting and I don't really see a need for tempered
glass (unless for safety), but you will soon be told it really can't be cut.
Certainly standard glass will cut fine, but for thin strips you really need
to have the same amount of glass on each side of the score line for success
(i.e. always cut pieces in halves). What are the final dimensions you need?

-Bruce