Specifications

.110”, but it should have been .108”.
This will not affect most locksmiths,
since you don’t manufacture your
own pins. This dimension has been
used in other articles, that’s why I
originally thought it was correct and
it’s best to catch this stuff early
before it is presumed to be fact.
I also made reference to a
calculation to
determine
the control
key cuts.
When I have
taught this
subject in a
class, I have
emphasized
that the for-
mula only
works when
the core has
been coded
correctly and
according to
the rules. I did
not stress that
sufficiently in
the article. It
is possible to
use an improper size top pin in a
chamber and not affect the operation
of the lock. This is sometimes done
accidentally, but also is done
intentionally to deceive someone
attempting to decode the control key.
If you run across such a core, you
can still decode the control key. It
just takes a little more work to
accomplish the task. You must
measure all the other pins except
the top pin and determine the stack
height. Subtract that number from
what should have been the correct
stack height if a correct top pin was
used, and that will tell you what
should have been the top pin size.
All you have to do is subtract that
number instead of the size of the
actually used top pin and you will
have the correct control key cut.
The other item has to do with the
graphic representations which
showed how to determine the pin
sizes. For A-2, A-3 and A-4 they
looked like a stack of pins with the
required computations printed
inside. The original source for those
graphic depiction’s was not
identified by me in the article. They
were originally created by A. J.
Hoffman (formerly with Corbin
Russwin). He also pointed out the
errors (to me) mentioned above. My
thanks to A.J. for correcting those
errors, and my sincere apologies to
him for not identifying him as the
source for the graphics.
24 • The National Locksmith
11. The purpose of the dome face plug is to reduce the
likelihood of key breakage, by placing most of the stress
during key rotation on the key shoulder rather than the
key blade.
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