by Raymond » 13 Mar 2010 0:28
Ball bearings have been used primarily in Corbin/Russwin locks forever. But the original purpose was to prevent wear on the tips of the pins. These ball bearings are the full diameter of the normal pins, .115". The ball just rolls over the key and there is much less friction. Insert a ball, load a master pin to be flush with the shear line, and load a spool top pin. On these locks the springs had a small brass rod inserted inside them to prevent picking by over lifting. Coincidently, I added three ball bearings to a lock in a bank vault day gate just last week because they keep wearing out the lock pins.
The three very small bearings are probably part of a construction key set up. Or they may be planned to make a combo change without removing the lock. With the balls in between pins or master wafers, they are included in the length of the bottom pin stack which will equal a specific key depth.
If a key raised the three balls above the shear line, and this key had a slot cut into the bottom of the blank, the balls would fall into the slot when the key was rotated. When the key is withdrawn, the balls will be pulled out of the lock and fall away intended to be lost. Now only a key cut one depth higher (the thickness of one ball) will raise the same pin stack to the shear line. This lock has now been rekeyed on one pin by one depth. Note that the old key will no longer work and because it is now too low, cannot be made to work.
Another style of this construction keying uses holes drilled in line with the original pin holes on the plug. They are a smaller diameter than a normal pin and the normal pin passes over them without hesitation. When the higher key is used, the bearings are now above the shear line. As the plug is rotated, the balls fall into the extra small hole and are permanently trapped there. This lock is now rekeyed.
Nothing is foolproof to a talented fool. Wisdom is not just in determining how to do something, but also includes determining whether it should be done at all.
