On 20/06/2020 13:09, Smolley wrote:
On Sat, 20 Jun 2020 10:38:10 +0100, Adrian Brentnall wrote:

On 20/06/2020 10:02, Tricky Dicky wrote:
There was an example of glass cutting on the Repair Shop, specialist
glazer was brought in to cut some panes for a Victorian gas lamp. He
scored the glass with a single stroke of a diamond no lubricant. He
simply held the glass in his fingers either side of the score and with
a slight twist of the wrists it split cleanly.

Richard


All depends on the glass - the thinner the glass the easier it snaps.
I use some 2mm glass in my fused-glass jewellery, and it snaps as easily
as a chocolate bar - 2mm picture-frame glass is equally cooperative.

Modern 'stained-glass' glass tends to be 3mm - again, fairly easy to
work with.

4mm float / mirror glass takes a bit more effort. Scoring the surface of
the glass creates a line of weakness along which you'd like the glass to
break. Bending the glass by as little a 2 - 3 degrees causes it to break
along this line of weakness (hopefully).
In glasswork we use a pair of 'running pliers' - like the ones unsed in
ceramic tile work, which are designed to apply the correct pressure to
run the score..

Given that this is the op's first attempt, and he's only got one chance
to get it right, he probably needs all the help he can get!

It's probably just me getting old & crabby, but the more often I see
anything on TV that I know a little about (like stained-glass on the
Repair Shop), the more often I find myself shouting "You don't do it
like that!" at the TV.
These programs are produced for entertainment, not education....

It took me three attempts to get a half decent edge and taking off about a
foot of glass. I bought a 'professional diamond glass cutter' and it was
crap. It became blunt very quickly. I ended up using a new, tungsten
carbide tipped two fluted end mill, which gave a deep score.


Strangely, a lighter score (so it's only just visible on the surface of
the glass) works better, and you're more likely to get an accurate break.

I had it described to me once, that the glass is like a toy balloon -
the outer layers (top & bottom) are the rubber - the main body of the
glass is the remainder of the thickness.

All you're doing with the glass 'cutter' is to create a line of weakness
by cutting into the outer skin. Then, with the correct amount of force /
angle, you'll persuade the main body of the glass to break along the
line of the score..

Scoring the line too deeply causes the surface glass to splinter (you
can see fine glass-dust along the score-line) and then the core is
likely to run off in random directions.

When I've taught people who to do stained-glass, we spend an amount of
time with sheets of horticultural (greenhouse) glass - learning just how
much pressure is required when scoring. Straight lines first, then arcs
and onto snakey-lines!
Different colours and types of glass require different pressures - after
a while you instinctively adjust the scoring pressure to suit the piece
of glass you're cutting.