"Ziggur" wrote in message
T...
In article , says...
However, toughened glass is *vastly* stronger than ordinary (or
laminated)
under most circumstances - hence its name.

Dave

Does it ever occur to you before you post that, although you may be the
group's resident "expert" on expensive power tools, there are some in
here who have moderate knowledge on other specialist topics?

Toughened glass has, on average, 4.5 times more resistance to breakage by
impact than normal annealed glass. That resistance is measured by
swinging a leather bag filled with lead shot on the end of a chain at the
glass surface. This archaic test is the current British Standards method.
It confirms that if the glass is impacted by a football or a head or a
similarly large object it will resist breakage by a factor of "up to" 5
times the level for annealed glass. HOWEVER - most burglars and all
glazing professionals know that this extra strength is limited to these
conditions. A hard tap with a hammer and nail or a jab with a steel bar)
near the edge of a toughened glass pane will cause it to break more
easily than an identical blow on annealed or laminated glass.

Bottom line. The OP asked about thickness and the risk of breakage.
SAFETY glass is about SAFETY, not SECURITY. It breaks, but not
dangerously.

Join me for a trip around a Pilkington or a Saint Gobain factory and then
we can talk about De Walt on the way home

Actually your and Dave Plowman's post together illuminated the subject
greatly for me, Dave underlining rather than contradicting your advice. I
have picked previously up that safety and security are different things. I
am not worried about security in this instance, only working strength, and
safety. My last post above gives an anecdote that of course fits your
information on glass strength. I have practical experience of how weak
toughened glass can be when provoked!

What I want to do is see if we can't replace the annealed glass that -was-
in an existing door at my Mother's house with new glass that will not break
in what will probably be careful daily use by my Mum, and IF it does break,
causes little or no injury. My Mum's usual general builder wants to replace
the whole door, saying that the rebate in the existing door will only take
4mm glass. It seems to me from what I have read that 4mm toughened is OK for
my application. I am left wondering if patterned 4.1mm toughened is still
strong enough as the pattern must surely weaken the pane, due to the pattern
making the glass less than 4.1mm in any grooves?