The direction to turn the plug depends on the bolt mechanism, not on the lock, but here are some general rules. Cheap padlocks will open if the plug is turned in either direction, so you can chose the directionh which is best for the torque wrench. All padlocks made by the Master company can be opened in either direction. Padlocks made by Yale will only open if the plug is turned clockwise. The double plug Yale cylinder locks generally open by turning the bottom of the keyway (i.e., the flat edge of the key) away from the nearest doorframe. Single plug cylinder locks also follow this rule. See Figure 9.1. Locks built in to the doorknob usually open clockwise. Desk and filing cabinet locks also tend to open clockwise.
When you encounter a new kind of lock mechanism, try turning the plug in both directions. In the correct direction, the plug will be stopped by the pins, so the stop will feel mushy when you use heavy torque. In the wrong direction the plug will be stopped by a metal tab, so the stop will feel solid.
Figure 9.1:Direction to turn plug
Turning a lock more than 180 degrees is difficult because the drivers enter the bottom of the keyway. See section 9.11.
When you encounter this situation, release the torque and start over by concentrating on the back pins. Try a light torque and moderate pressure, or heavy torque and heavy pressure. Try to feel for the click that happens when a pin reaches the sheer line and the plug rotates slightly. The click will be easier to feel if you use a stiff torque wrench.
Deformation can be used to your advantage if you want to force several pins to bind at once. For example, picking a lock with pins that prefer to set from front to back is slow because the pinsset one at a time. This is particularly true if you only apply pressure as the pick is drawn out of the lock. Each pass of the pick will only set the frontmost pin that is binding. Numerous passes are required to set all the pins. If the preference for setting is not very strong (i.e., the axis of the plug holes is only slightly skewed from the plug's center line), then you can cause additional pins to bind by applying extra torque. Basically, the torque puts a twist in the plug that causes the front of the plug to be deflected further than the back of the plug. With light torque, the back of the plug stays in its initial position, but with medium to heavy torque, the front pin columns bend enough to allow the back of the plug to rotate and thus cause the back pins to bind. With the extra torque, a single stroke of the pick can set several pins, and the lock can be opened quickly. Too much torque causes its own problems.
When the torque is large, the front pins and plug holes can be deformed enough to prevent the pins from setting correctly. In particular, the first pin tends to false set low. Figure 9.2 shows how excess torque can deform the bottom of the driver pin and prevent the key pin from reaching the sheer line. This situation can be recognized by the lack of give in the first pin. Correctly set pins feel springy if they are pressed down slightly. A falsely set pin lacks this springiness. The solution is to press down hard on the firstpin. You may want to reduce the torque slightly, but if you reduce torque too much then other pins will unset as the first pin is being depressed.
It is also possible to deform the top of the key pin. The key pin is scissored between the plug and the hull and stays fixed. When this happens, the pin is said to be false set high.
The problem with a loose plug is that the driver pins tend to set on the back of the plug holes rather than on the sides of the holes. When you push the plug in, the drivers will unset. You can use this defect to your advantage by only applying pressure on the outward or inward strokw of the pick. Alternatively, you can use your finger or torque wrench to prevent the plug from moving forward.
Figure 9.2: Driver pin false set by elastic deformation
The top half of Figure 9.3 shows a pin column with a driver pin that has a larger diameter than the key pin. As the pins are lifted, the picking pressure is resisted by the binding friction and the spring force. Once the driver clears the sheer line, the plug rotates (until some other pin binds) and the only resistance to motion is the spring force. If the key pin is small enough and the plug did not rotate very far, the key pin can enter the hull without colliding with the edge of the hull. Some other pin is binding, so again the only resistance to motion is the spring force. This relationship is graphed in the bottom half of the Figure. Basically, the pins feel normal at first, but then the lock clicks and the pin becomes springy. The narrow key pin can be pushed all the way into the hull without loosing its springiness, but when the picking pressure is released, the key pin will fall back to its initial position while the large driver catches on the edge of the plug hole.
The problem with a large driver pin is that the key pin tends to get stuck in the hull when some other pin sets. Imagine that a neighboring pin sets and the plug rotates enough to bind the narrow key pin. If the pick was pressing down on the narrow key pin at the same time as it was pressing down on the pin that set, then the narrow key pin will be in the hull and it will get stuck there when the plug rotates.
The behavior of a large key pin is left as an exercise for the reader.
A lock with beveled plug holes requires more scrubbing to open than a lock without beveled holes because the driver pins set on the bevel instead of setting on the top of the plug. The plug will not turn if one of the drivers is caught on a bevel. The key pin must be scrubbed again to push the driver pin up and off the bevel. The left driver pin in Figure 9.6a is set. The driver is resting on the bevel, and the bottom plate has moved enough to allow the right driver to bind. Figure 9.6b shows what happens after the right driver pin sets. The bottom plate slides further to the right and noe the left driver pin is scissored between the bevel and the top plate. It is caught on the bevel. To open the lock, the left driver pin must be pushed up above the bevel. Once that driver is free, the bottom plate can slide and the righ driver may bind on its bevel.
If you encounter a lock with beveled plug holes, and all the pins appear to be set but the lock is not opening, you should reduce torque and continue scrubbing over the pins. The reduced torque will make it easier to push the drivers off the bevels. If pins unset when you reduce the torque, try increasing the torque and the picking pressure. The problem with increasing the force is that you may jam some key pins into the hull.
Figure 9.3: Driver pin wider than key pin
Figure 9.4: Beveled plug holes and rounded key pins
Figure 9.5: (a) Driver sets on bevel
Figure 9.6: (a) Driver jams on bevel
If you pick a lock and the plug stops turning after a few degrees and none of the pins can be pushed up and further, then you known that the lock has modified drivers. Basically, the lip of the driver has caught at the sheer line. See the bottom of Figure 9.7. Mushroom and spool drivers are often found in Russwin locks, and locks that have several spacers for master keying.
You can identify the positions with mushroom drivers by applying a light torque and pushing up on each pin. The pins with mushroom drivers will exhibit a tendency to bring the plug back to the fully locked position. By pushing the key pin up you are pushing the flat top of the key pin against the tilted bottom of the mushroom driver. This causes thedriv er tostraigh ten up which in turn causes the plug to unrotate. You can use this motion to identify the columns that have mushroom drivers. Push those pins up to sheer line; even if you lose some of the other pins in the process they will be easier to re-pick than the pins with mushroom drivers. Eventually all the pins will be correctly set at the sheer line.
One way to identify all the positions with mushroom drivers is to use the flat of your pick to push all the pins up about halfway. This should put most of the drivers in their cockable position and you can feel for them.
To pick a lock with modified drivers, use a lighter torque and heavier pressure. You want to error on the side of pushing the key pins too far into the hull. In fact, another way to pick these locks is to use the flat side of your pick to push the pins up all the way, and apply very heavy torque to hold them there. Use a scrubbing action to vibrate the key pins while you slowly reduce the torque. Reducing the torque reduces the binding friction on the pins. The vibration and spring force cause the key pins to slide down to the sheer line.
The key to picking locks with modified drivers is recognizing incorrectly set pins. Mushroom driver set on its lip will not have the springy give of a correctly set driver. Practice recognizing the difference.
In general, spacers make a lock easier to pick. They increase the number of opportunities to set each pin, and they make it more likely that the lock can opened by setting the all the pins at about the same height. In most cases only two or three positions will have spacers. You can recognize a position with a spacer by the two clicks you feel when the pin is pushed down. If the spacer has a smaller diameter than the driver and key pins, then you will feel a wide springy region because the spacer will not bind as it passes through the sheer line. It is more common for the spacer to be larger than the driver pin. You can recognize this by an increase in friction when the spacer passes through the sheer line. Since the spacer is larger than the driver pin, it will also catch better on the plug. If you push the spacer further into the hull, you will feel a strong click when the bottom of the spacer clears the sheer line.
Thin spacers can cause serious problems. If you apply heavy torque and the plug has beveled holes, the spacer can twist and jam at the sheer line. It is also possible for the spacer to fall into the keyway if the plug is rotated 180 degrees. See section 9.11 for the solution to this problem.
Figure 9.7: Mushroom, spool, and serrated driver pins
Figure 9.8: Spacer pins for master keying
Figure 9.9: Spacer or driver can enter keyway
Figure 9.10: Workings of a disk tumbler lock