The Wafer Tumbler Lock
The wafer tumbler lock was developed as a low-cost lock that offered a reasonable degree of security
to the owner. These locks are make
up over one-fourth of all the locks in the world. The
outside of the lock resembles the pin tumbler lock (yet to be discussed), but uses a
much
simpler mechanism. Wafer keyways usually have simple side ward indentions. The key is usually
shorter than that of other
locks, but equally broad. It may be cut on one or both sides. A two
sided wafer lock is often called a "double wafer." The lock consists of
four main
parts. The plug housing, which contains the wafers and springs, the shell, the cam (locking bolt),
and the retainer. The wafers
are sometimes referred to as "discs" because their top
and bottom are rounded to fit into the cylinder. Here is a diagram:
5
___
7 | ___
||############## 1-> @| _ |_
## ||## ## ## ## ## @||2||/
6##||##4##3##2##1## <-keyway @||_||
## ||## ## ## ## ## \|___|
___||##############
3
|
\plug/ detail of a wafer tumbler
cutaway side view 1) spring
of a
wafer lock 2) key slot
3) spring wing
1-4) spacings #1-4
5) cam (operates
the bolt)
6) retainer (rear plug)
7) the shell (body of the lock)
Each lock has a series of chambers in which the wafers rest. These spacing closest to the front of
the lock is numbered with one, and
their numbers increase toward the back of the lock. Picture
a number of the wafers placed face-to-face in the plug’s spacing chambers.
Each wafer is equal
in overall size, but the key slots are of varying height. A metal spring exerts pressure on the
spring wing of each
wafer, forcing its lower part into the shell’s "locking grooves"
which lets the lower portion hang about midway into the keyway.
Looking into the lock, you
should be able to see this. These wafers act to hold the plug and shell together, preventing the
lock from
turning.
When the correct key is inserted, it goes through the key
slots on each wafer, raising the wafers out of the locking groove. The key must
have the
appropriate depth of cut in each position to raise the wafer the correct amount. The depth of the
key’s cut (and the length of
the wafer’s key slot) is any one of five different depths. The
shorter the top edge of the wafer’s key slot, the lower the key cut depth
value. For instance
the number 1 slot (the slot that is the largest) would require the shallowest cut in the key.
Normally lock
manufacturers place a number four or five wafer near the keyhole to block the
view of the back wafers. Also note that the same type of
wafer may appear several times in the
same lock.
Above some brands of wafer tumbler lock you will see a small hole. When the
lock has been unlocked, you can remove the entire lock
plug by inserting a piece of stiff wire
into this hole and depressing the retainer. Though nowhere near as secure as the pin tumbler
lock,
the wafer tumbler is a very popular, low cost lock. The lock is normally found on
cheaper cabinets and desks, some padlocks, some
automobile locks, locking handles, and trailer
doors. Where more security is desired, the double wafer type is used, providing wafers on
the
top and bottom of the keyway.
Picking
Though harder to pick then the
warded lock, the wafer lock is still easy to circumvent. This is an excellent lock to practice on
because
the techniques required to pick it are applicable to the pin tumbler lock as well.
Like the lever lock, picking the wafer tumbler lock
requires use of a tension wrench and a
pick. A variety of the different picks can be used including the rake, the hook, the
half-diamond,
and the half-round pick. Selection depends on the size of the lock, the distance
between each wafer, and personal preference.
Raking
One of the most
common methods of picking the wafer tumbler lock is by raking. To rake the lock, insert the tension
wrench is inserted
just inside the keyway, stopping short of the first wafer, and flush with
the bottom of the keyway. Apply moderate tension to the
wrench. If you apply too much tension
the wafers will bind and not be able to move into alignment. Once you have the tension wrench
in place, insert either the rake or half-round pick into the keyway. Don’t worry about feeling the
tumblers, instead concentrate on
applying uniform pressure to them as you move the rake in and
out of the keyway in a scrubbing motion. This scrubbing motion
should cause the wafers to lift
into alignment as they are thrown up and down in their spacings. This method is usually quite
effective
on most wafer locks, and should always be tried first.
Manipulating
Individual Wafers
If the lock does not respond to raking, you can try using the
half-diamond pick to each wafer into alignment one-by-one. While
maintaining light but
consistent pressure with the tension wrench, use the pick to lift each wafer into alignment at the
shear line,
starting from the backmost tumbler. Once it reaches the proper alignment, you
should feel or hear a slight "click" and the plug will turn
ever so slightly,
relieving a bit of pressure on the wrench. Continue one-by-one, working outward, until each tumbler
has been aligned
and the lock opens.
Vibration Picking
Often you
can use a technique called vibration picking to open a wafer tumbler lock. This uses a tool known as
a "snapper" pick or a
"lockpick gun". [These are described in the
Lockpicking Tools section of this article] To use the snapper pick maintain a light tension
with the wrench and insert the tip of the pick into the keyway, just touching the bottom of the
tumblers. Then use the thumb, which
rests along the top edge of the pick to depress the top
loop. Let the thumb slide off the compressed part of the pick, permitting it to snap
back. It
will then strike a light blow to the tumblers, popping them up until they are held in place at the
shear line. Repeated snaps,
while maintaining tension with the wrench, usually results in
aligning all the tumblers, and thus opening the lock. The lockpick gun
works automatically,
with a trigger device that "snaps" its wire pick up in the keyway.
Picking
Double Wafer Locks
Double Wafer locks are picked the same way as single wafer locks,
but there two sides to the story. Not only must you align all the top
wafers, but the bottom
ones as well. You can purchase special designed tension wrenches with will let you then use a ball
pick to pick
both sets of wafers. Alternatively you can use a standard tension wrench in the
center of the keyway, using a half diamond pick. Once
you have picked one set, simply reverse
the pick and pick the other. It may take a few tries before you are able to hold all the wafers
in
place.
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