they can be very effective and
You must know the appropriate key gauge for the key; there
isn’t one key gauge that works
for all key bitting specifications
and utilizing the wrong key
gauge on a key will accomplish
nothing more than wasted time.
Micrometers offer the most
accurate method of decoding a
key (photo 6). Micrometers allow
you to take actual measurements
of the key, usually with accuracy
± .001”, regardless of the key
blank or the key bitting specifica-
tion. This information can then
be used to determine the key bit-
ting specifications out right.
The process to decode using a
micrometer is rather straight forward. In fact, there is a formula
for this process that you should
commit to memory: Effective
Plug Diameter – Root Depth =
Bottom Pin Length.
The effective plug diameter
varies by manufacturer but this
information is readily available.
If you utilize universal LAB pin
kits this measurement is listed on
each pinning chart. LAB labels
this measurement as E.D., which
stands for effective diameter. It
should be noted and stressed
that effective plug diameter is not
plug diameter does not.
Avoid confusion by also
this to memory.
depth is what
The root depth is amount of
material, for lack of better words,
between the bottom of the key
blade and the bottom of the key
cut (photo 7). By taking this
measurement and subtracting it
from the effective plug diameter,
or what is needed to create the
shearline, we are determining
the correct length of the bottom
pin. All measurements are taken
within a thousand of an inch so
you will need to compare the
results of this formula against the
manufacturer’s key bitting speci-
fication to determine the bottom
pin/cut assigned to it. Bottom
pins correspond to the cut, which
simplifies things for everyone
involved. For example, if your
formula produces a difference of
.270” and it is the Schlage classic
key bitting specification then you
can safely assume you have a 7
cut which utilizes a 7 bottom pin.
Measuring with a micrometer
and comparing, or even deriving, is nearly always slower than
other decoding methods but it is,
without a doubt, the most accurate and fool proof method (photo
8). An added benefit of a micrometer is that they are multipurpose. You can use micrometers
to measure other things, such as
pins. They are also very helpful
when calibrating key machines
as they can provide precise
measurements throughout the
Once you become very proficient with a key bitting specification or specifications, you can
begin to visually decode keys.
This process allows you to determine key cuts by using visual
clues of the key. It takes some
skill to become accurate with it
but if you are become good at it,
and the key is accurate, then you
can decode keys almost as fast as
if it were a direct code.
I utilize all options and I would
advise you to as well. Keep key
gauges and a micrometer on the
truck and in the shop. Make sure
you have access to code books or
software. The situations at hand
will determine the best, or perhaps only, method of decoding.
It is a good idea to not only have
those methods available to you
but also to be proficient at them.
6. A micrometer.
8. Key bitting specifications can greatly assist when
decoding keys with a micrometer.
7. A micrometer measuring the
root depth of a key cut.