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glass cutting




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From:  Steve Falco [SMTP:sfalco-at-worldnet.att-dot-net]
Sent:  Saturday, February 28, 1998 2:45 PM
To:  Tesla List
Subject:  Re: glass cutting

Tesla List wrote:
I had a similar experience with a piece of glass salvaged from a very
old TV, back when they used to have a separate piece of protective glass
in front of the picture tube.  (Now of course they have an integral
safety glass in front.)

Anyway, I thought it was regular plate glass, so I scored it and tried
to snap it over a nail, the way I cut any other window glass.  I
literally stood on the glass and bounced up and down, and it took my
abuse for more than a few seconds!!!  Then it exploded exactly as you
described.  Little tiny bits of (not very sharp) glass shot all over the
basement.  What a mess to clean up.

I later learned that this was a specially tempered safety glass, with
deliberate internal stresses that are designed to have it break into
small pieces to avoid injury when it finally lets go.  And it doesn't
let go easily.  Automobile glass is similar, and if you have ever had a
car window broken, you know how it makes little chunks.  (The front
windshield has a plastic layer bonded in the center to contain the
fragments in an accident, but the side and rear windows usually don't.)

	Steve Falco

> ----------
> From:  Eleanor Flood [SMTP:eflood-at-bellsouth-dot-net]
> Sent:  Monday, January 12, 1998 2:01 PM
> To:  tesla-at-pupman-dot-com
> Subject:  glass cutting
> 
> If anyone out there is planning on making plate glass caps, please be
> warned, our neighbor gave us a couple of fine sheets of Hercules Safety
> glass.  The sheets were 24" long and 8" wide. Harold thought to saw them
> into 8" square pieces to make a glass cap. I do a bit of lapidary work,
> so we have a diamond edge abrasive saw that is used to cut rocks, glass
> and the like.  Harold marked the glass, donned a rubber apron, a hat and
> safety goggles, and turned on the saw.  He had not cut an eighth of an
> inch into that glass when it literally exploded.  There was not a piece
> of it left as big as a match head.  The glass was scattered all over the
> 10' x 24' room.  We have no idea what was so different about this glass
> to cause such an event. He frequently saws regular window glass and
> glass bottles for salt water caps with no problem.  Anyway, if you plan
> to saw glass, just be careful.  We also wonder what might have happened,
> should he have had access to the size he needed, constructed the cap and
> put the high voltage to it.  Big explosion?  Anyone know anything about
> this type glass.
> 
> Safe sparking, and safe sawing!
> Elli