by jwhou » 25 Apr 2010 20:43
The regular barrel driver pins hold the plug to cylinder alignment better than the classic spool pins but spool pins with multiple cuts can also hold the alignment well as do serrated pins. Ideally, you would want the last pin picked to hold the alignment very well, since you don't know what order the pins will be picked, the recommendation is usually for the back pins to be regular barrel pins so that the last pin lifted by the key holds the plug alignment well till lifted. Note that the purpose of the sidebar is also to hold the plug alignment as long as possible. The better held the alignment is, the less of an offset there is for lockpickers to take advantage of to set the pins.
Note that Masterlock's article entitled "New Anti-Bump Technology from Master Lock by Billy Edwards, CML" which described the development process for their bumpstop product mentions that high speed video disproved the Newton's Cradle theory and that lock-bumping actually worked cause the top driver pins were stopping on the shear line on their way back down and that the bottom and top pins did not separate till then. This would be consistent with some people observing that a stronger springs and or taller pinstacks seem to make the locks more bump resistant since the greater spring force would make the driver pin more likely to re-enter the plug when torque is applied to the plug (note some people claim that shorter pinstacks made the locks more bump resistant but that's probably more resistant to more minimal energy techniques that do not bounce the short pin stacks enough). This would also explain why mushroom pins tended to offer better bump resistance than spoolated pins as a mushroom pins bottom is more rounded and hence more likely to re-enter the plug. The inverse taper of the Bumpstop pin is a smaller diameter making it more likely to re-enter the plug as well and they experimented with normal tapers for plug re-entry prior to the inverse taper but found the bump resistance didn't last with the regular taper. This would also mean that using bottom pins as top pins perhaps as part of a compensated driver attempt would also provide limited bump resistance although such a scenario would introduce other security weaknesses.
One of the best ideas that I've heard of is actually from one of the discussion forums here where someone recommended that a pin chamber be sacrificed with the chamber in the bible over-drilled to accommodate a ball bearing that would seat in the pin chamber in the plug but not enter it, then a spring could be put in and the compression adjusted with a set screw effectively making a torque limiter as in a torque wrench. This means that the torque applied to the plug must exceed a certain level before the ball bearing unseats therefore the plug alignment is held regardless of the pins till there is so much torque as to make single pin picking and lock-bumping impractical due to how much the pins would be binding by. I would add that either a set screw be inserted into the pin chamber in the plug to prevent the ball bearing from being lifted by a pick or the whole concept be offset from the keyway perhaps by creating an auxiliary bible by threading a pipe segment into the cylinder housing (note that such an offset approach could house a trap pin if a small enough ball bearing is used).
I think that there are enough people unaware of the driver pins role in holding plug alignment precisely enough to make lock picking difficult that they succumb to the concept of having all the driver pins be security pins. This is just like how there are mechanics out there who erroneously believe that a 100% anti-freeze solution provides more protection than the recommended 50/50 solution. I wouldn't be surprised if the corporate decision to make a given lock all spoolated drivers have been made by people unaware of the plug alignment function that driver's provide. You'll even find a youtube video of a guy picking a Kwikset lock with all spoolated top drivers and calling that a Kwikset on steroids.
