Cylindrical And Mortise Lock Functions

When I first started doing lock work, I was told to be very careful and read the packaging to be certain the lock installed onto the door was the correct finish and operation. My early jobs were restricted to cylindrical and tubular locks. Living in California, we mainly installed Schlage and Kwikset cylindrical and tubular locks. The Schlage factory was in the Bay area and Kwikset was in Anaheim.

Most of my installs at the time were Passage locks, Emergency Key locks (Privacy), All Purpose locks (Entry), and Storeroom locks. The All Purpose Schlage knobset was the A52PD or the A52WD, which is equipped with a ”universal” button. To provide an additional choice for customers, we also sold the A51PD/WD, which is equipped with a turn-button. The difference is whether the inside button would release, unlocking the door when the key or the inside knob was turned. The Schlage A51PD would not release the button when operated by the key or the inside knob.

There were many more “A”, “C” and “D” locks having unique operations in the 1950 Schlage Lock catalog.  “A” knobsets could be ordered in 12 lock operations equipped with pin tumbler or wafer lock mechanisms. For example, the A52PD description was “Recommended for ENTRANCE or CORRIDOR DOORS. Rotating either knob will retract latch bolt. Pushing button in inside knob locks outside knob. Rotating inside knob or turning key releases button automatically. Closing door does not release button. Button may be fixed in locked position by rotating to horizontal position. Lock may be opened by key from outside. Inside knob always free for immediate exit. Latch bolt automatically deadlocks when door is closed.”

The extra duty construction “C” and “D” locks could be ordered choosing from 25 operations. The “C” knobsets mechanism is constructed of non-ferrous metals throughout. Spindles and latch bar are of Monel metal; all other parts are of bronze. “C” and “D” knobsets used the same knob and rose designs. However, they were not available with wafer lock mechanisms.

By the time I received my 1979 Schlage Service Manual, there were 22 “A” knobset operations with many of the wafer lock models discontinued. In this manual the A52PD/WD lock operation description was the same as the 1950 catalog.

Unlike mortise locks, cylindrical locks were for the most part interchangeable as the cross bore was usually 2-1/8” diameter at a 2-3/8” or 2-3/4” backset. However, not every lock manufacturer would include a full description of the lock’s operation in their catalogs. This could add uncertainty when it came to ordering a lock if the customer wanted a different manufacturer’s lock. Lock operation could have minimal variation, for example the Schlage A51 and A52 locks.

To resolve this potential problem and expand upon standardization, Builder’s Hardware Manufacturer’s Association (BHMA) became involved with the federal government. Many years prior to the involvement, the Federal Government had developed a series of lock specifications. However, there was no set organization or standardization.

Through their involvement in 1970, the BHMA’s standard for Function “F” numbers was developed. Additional numbers are being added to keep the standard up to date. This voluntary standard was slowly accepted and incorporated by lock manufacturers into their catalogs.

BHMA and American National Standards Institute (ANSI) instituted ANSI Function numbers to describe lock operation. A lock function is the operating features of a particular type of lock that makes it suitable for a specific application. The function is how a lock behaves when operated. The standard was created, with specific ANSI numbers for locks (knob and lever cylindrical), bored dead latch locks (deadbolt), interconnected locks and mortise locks. At this time, electrified locks do not have a function number.