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© Copyright 2006, Sargent & Greenleaf, Inc.
Model 6730, 6735, 6738, 6741 Mechanical Combination Lock
Troubleshooting/Dialing Diagnostics
a fLy in the ointMent
Let’s stand back for a moment, and do a quick review of wheel
construction. The travel of a movable fly is the distance the
fly can move within the confines of its milled area in the wheel
center. The amount of travel is expressed in dial numbers,
and is typically between 10 and 12. The amount of travel is
not chosen arbitrarily, but is equal to twice the width of the fly
plus the width of the associated drive pin. This is the opti-
mum amount of fly travel which will allow use of every number
on the dial in selecting a combination.
No matter where a
fly may be stuck, out
dialing diagnostics
will show the affected
wheel picking up
before it should by a
number equal to the
total possible travel
of the fly (expressed
in dial numbers). In
the case of current
production S&G locks, the number is 10. This 10 number off
pickup indicates the fly is stuck, but not where in its travel the
sticking occurs. Suppose we picked up wheels at the following
places during our dialing procedure:
1st turn 61 3rd wheel fly is okay
2nd turn 51 2nd wheel fly is stuck
3rd turn 52 1st wheel fly is okay
At first glance, you might assume the 1st wheel fly is also
stuck. However, because it picks up within 2 numbers of
where the #2 wheel picked up, we know the #1 wheel fly is
okay. Remember, as we turn the dialing procedures, try some-
thing simple. A sharp, snapping dial action whenever direc-
tion is reversed will often shove the fly to its limit, despite any
burr or debris which may be in its way. This will allow you to
use the actual combination numbers and avoid the more time
consuming procedure which follows. If snapping doesn’t work,
it will be necessary to resort to some simple math.
Chances are excellent a fly will stick at one of the extreme limits
of permissible travel, and this makes dialing open the lock
pretty straightforward. For a Sargent & Greenleaf three-wheel
lock, use the following directions for whichever case you diagnose.
Fly on wheel #1 is stuck:
Subtract 10 from the 1st combination number
Dial 2nd and 3rd number as usual
Fly on wheel #2 is stuck:
Dial 1st number as usual
Add 10 to 2nd combination number
Dial 3rd number as usual
Fly on wheel #3 is stuck:
Subtract 10 from the 1st combination number
Because most situ-
ations involve the
fly sticking at the
extreme limit of
travel, one of these
procedures will
open the lock most
of the time. After
the combination
is dialed, return to
the contact area of
the lock (between
#6 and #14) and
oscillate the dial
between the two
metal-to-metal contact points. If the internal parts of the lock
are almost lined up to allow the lever to fall and open the lock,
this vibration may finish the job for you. Anytime you are dialing
to open a stubborn lock, oscillation
of the dial in the contact area can help.
LIMITS OF FLY TRAVEL
DETERMINED BY
MILLED AREA OF
THE WHEEL CENTER
THE CONTACT AREA
IS THE WIDTH OF THE
DRIVE CAM GATE,
MEASURED IN DIAL
NUMBERS
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