48 • HISTORYOFLOCKS
Locksmiths Inspiring
Locksmiths
Everybody knows the Chubb Security Range
lock, the 3G110, sometimes also known
as the Castle Security Range. Some long
standing locksmiths will also know that it
was Bill Stanton, whilst with Chubb’s R&D
department, who developed and patented
the lock on behalf of his firm.
» » THE INSPIRATION, TO BILL, FOR THIS
lock was made by the German firm
Kromer and called the Se-Kro mortice
lock. The lock failed to establish for
Kromer. Bill had seen this lock on one of
his many trips to the Kromer factory and
felt he could not only improve the design
but also improve the security. This he
did and the lock, known as the ‘Chubb
Security Range’, after a few teething
problems soon became regarded as high
security and was used for commercial
grade applications used amongst other
things on the main front doors to banks.
The following is from Chubb’s training
notes and refers to the section on key
differing having first explained the
limitations of conventional levers it then
goes on to explain detainers: “Detainer
To further increase the key differing
whilst at the same time improving master
key systems, the open ended in figure
6 is used. This is the type of ‘lever’
incorporated in certain security range
locks. The lock incorporates five detainers
and uses a bolt throwing device which
not only operates the bolt but through
a mechanical linkage forces a probe
into the gates of the detainers at a pre-
determined height in accordance with the
stepping on the keys.
A typical five detainer key is shown in
figure 7. It will be noted that it has nine
steps, whilst it is necessary to retain a
symmetrical key, steps are not restricted
for bolt throwing and therefore it is
Fig.6
Fig.7
possible
to use
five steps
for effective
differing.
The open ended
detainer offers more scope
for differing than the ordinary
lever and in this particular case, we
are able to vary each key step in nine
different ways. In other words there
are nine lifts per step and by using
our normal mathematical formula; the
maximum key differing can be expressed
as being 95, which is 59,049.
Once again by ruling out the
undesirable keys we are left with positive
key differing in the region of 25,000
which is really quite exceptional for a
range of mortice locks. The additional
notch in the detainer shown in figure 6
is cut when the lock is made to operate
under a master key and here again one
can see the scope for manufacturing
these systems with a minimum loss in
security as opposed to the warded type of
key that can be so easily skeletonised.
This method of determining key
differing can be applied to most lock
mechanisms provided one knows the
number of steps that can be used
effectively and the number of variations
LOCKSMITHJOURNAL.CO.UK | JAN/FEB 2019
An early version of the Chubb 3G110.
Note also the nylon bolt thrower.
Experiments with both nylon and
sintered iron were experimented with
in the pre-production prototypes.
that can be applied to each step them
the formula can be applied.”
Most locksmiths know that the end
gated lever had been used as early as
the first years of the 19th century by
makers like Walton. More latterly Francis
Butter, of Josiah Parkes (Union’s Butters
System) had the very successful lock
of that name and of course with the
mastering possibilities. In both cases the
bolt throwing steps of the key severely
limited both the security and mastering
possibilities. Wards were still used to
help address these shortcomings.
As mentioned earlier Bill Stanton, who
was already a fan of Francis Butter and
his system, had seen a mortice lock on
one of his trouble shooting trips to the
Kromer factory; and so inspired; he set
about addressing the issues to turn it
into a viable security lock. The Chubb
(today branded as Union) Security