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© Copyright 2006, Sargent & Greenleaf, Inc.
Model 6730, 6735, 6738, 6741 Mechanical Combination Lock
Troubleshooting/Dialing Diagnostics
Loose sPLine key
Proper installation of the correct spline key will prevent this
problem from occurring. The proper spline key is one which fits
snugly into the keyway milled into both the drive cam and
spindle. You should not be able to insert and remove it with
your fingers. It should be seated with a small, light hammer
and require side cutters or a spline key removal tool to extract.
A properly seated S&G spline key is oriented with the flag over
and just touching the drive cam. Before 1988, spline keys
were meant to be oriented with the flag crossing over and just
touching the spindle. A spline key is a press-fit part, mean-
ing it is slightly deformed when it is seated. Upon removal, it
should always be discarded and replaced with a new, unused
one. The current spline key number for S&G Group 2 locks is
U17. Stocking and using new spline keys will prevent the prob-
lems we will cover.
The spline key ties the dial/spindle assembly directly to the
drive cam, making these components act as one part. When
the dial is turned any number of degrees, the drive cam
rotates exactly the same number of degrees…as long as the
drive cam stays firmly attached to the drive spindle. If the
connection is sloppy, due to a worn or undersize spline key, a
ten number turn of the dial will likely result in an eight or nine
number turn of the drive cam. In other words, drive cam rota-
tion lags behind the dial by a number or two, just enough to
keep the lock from opening.
Diagnosing a loose spline key can be tricky. A good safe ampli-
fier will help. It will let you hear metal-to-metal contact when
it might be too light to feel through the dial. With the amplifier
in place and adjusted, dial all wheels right to 60. Now turn left
directly to the lock’s contact area (typically between 6 and 14
on S&G Group 2 locks). Slowly oscillate the dial between the
contact points. If you can hear the lever nose striking the sides
of the drive cam gate a half number or more before you can
feel the contact through the dial, you may well have a loose
connection somewhere between the dial and the drive cam,
and the guilty part is usually the spline key.
Our combination is 4 times left to 20, 3 times right to 60, 2
times left to 40. With a loose spline key, dialing left to our first
number (20) would leave the #1 wheel at 18. Dialing right to
60 leaves the #2 wheel at 62, and dialing left to 40 leaves the
#3 wheel at 38. In this case, the two must be added to the
1st and 3rd numbers of the combination, and the two must be
subtracted from the 2nd.
An even easier way to compensate for a loose spline key is to
intentionally “over-dial” the correct combination numbers. No
matter which direction you are dialing, simply pass all the
combination numbers by the same amount. Start over-dialing
by one, and work your way up to five. The lock should open
sometime during this procedure.
stuck Lever
Occasionally, a drop lever will be forced against the lever stop
or will be affected by a bit of debris in the lock case, and it
will not fall into the drive cam gate even after the proper com-
bination is dialed. This is diagnosed by the lack of any contact
points during our dialing diagnostic procedures. Fortunately,
the fix is usually simple.
Dial the correct combination, then move the dial between the
numbers where the contact points should be. We’ll choose 10
for our S&G R6730 (remember, the contact points are about 6
and 14). Tape or hold the dial in this position. Strike the flat
surface of the safe door with a 2 lb. (or heavier) soft-face,
dead blow hammer. A dead blow hammer is filled with lead
shot. It’s designed to impart a greater percentage of the force
of a blow to the safe than an ordinary steel hammer, without
bouncing back. You can substitute a heavy metal hammer if
you use protective material over the safe door (a block of wood,
etc.). One or two blows will usually cause the lever to drop. You
won’t know for sure until you remove the tape and turn the dial
to retract the lock bolt. If the safe door has a handle which
activates the boltwork, tap it lightly in the locking direction.
This action will likely remove pressure from the end of the
combination lock bolt.
CORRECTLY POSITIONED LEVER
LEVER JAMMED AGAINST
LEVER STOP
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