X1X is operated by all keys. X2X is operated by 1AA, 3AA (but not AA). X3X is operated by 1AA, 2AA and 3AA (but not AA). We’ll use the same progression list as before. But, this time, we actually will use the TMK as a key. It’s our maintenance key. The other keys can stay the same. Here is the bitting list: maint sales Q.C. clean and X2X. X1X . 222 . . X2X . 2 . 2 . . 343212 door 343421 101 This looks wonderful. X1X is a lock pinned to four different keys with only three master pins, and none of them stacked. Doors 102, 105 and 107 are single-keyed locks; they don’t need any master pins at all. Of the remaining doors, 103 has exactly one master pin, 104A and 104B have two master pins, and 106 has three. We’ve gotten the total number of master pins down from 13 to just 11. But take a closer look at the pin- ning chart for X2X. Uh-oh: The 345621 key operates, even though it’s not supposed to. This is internal key interchange. The problem stems from the fact that there’s a lock in our keying chart that is operated by more than one key but not the designated master key. It needs to be cross keyed and NMK at the same time, which tends to cause problems with selective mas- ter keys from different columns of the KBA. Option A was immune to this problem be- cause the TMK itself was not in use. 36 KEYNOTES FEBRUARY 2022 102 103 104A 104B 105 106 107 2BB(NMK) 1BB 2BB 2BB 3BB(NMK) X2X 1BB(NMK) X1X is operated by all keys. X2X is opened by 2BB, 3BB and BB. X1X keying 345621 AA 365621 1AA 343621 2AA 345421 3AA Let’s write the pinning charts for X1X The problem might go away if we picked a different key to designate as the master. Let’s designate the cleaning crew key as the master. To avoid confusing it with the system above, we’ll call this al- ternate system BB. Look at each of the doors where the BB key does not oper- ate. In those cases, the lock has only one key. This will work. Below are our bitting list, keying schedule and pinning charts: maint sales Q.C. clean 545621 1BB 365621 2BB 343621 3BB 345621 BB “Progression gives us all the keys that are available for use in our system.” X1X 222 . . . X2X . 2 2 . . . 343212 343421 We’ve got our master pins down to just eight pins in eight locks. That’s amazing. And there’s no key interchange here. The BB master operates everywhere except 102, 105 and 107, each of which are single- keyed locks. However, we still run the risk that, at some later date, the customer will require a lock that operates with the sales key and the QC key but not the cleaning key, for example. That would be impos- sible with these bittings. However, if we knew in advance that this would happen, there’s a way to ac- commodate it. We would take the two crossed keys from the same column of the KBA. That eliminates the key inter- change, but it stacks the master pins. If you are eager to put your master key- ing skills to good use, you may find some situations like those listed here where you can use very few master pins, or even none at all. Ralph Forrest-Ball was a math teacher for 12 years before becoming a full- time locksmith. He joined ALOA in 1997 and earned the CML credential in 2009. From 2009 to 2019, he was the owner of Em- erald City Locksmith in Eugene, OR, and he was the winner of ALOA’s Best Shop con- test in 2011. He is currently working as an instructor and an author in Corvallis, Oregon. WWW.ALOA.ORG
