Understanding lost ball construction keying.
Applicable to PM8 design modules: Inline, Assa Abloy KeyUltra, Assa Abloy Perk, Assa Abloy Union, Lockwood Twin.
Construction keying is about having a key that operates cylinders during the building construction phase that can later be excluded from the cylinder when the building is occupied.
In one position the master key is cut deeper than the construction key by the size of the construction ball.
When the construction key operates the cylinder, the ball remains inside the core.
When the master key operates the cylinder with its higher cut in the construction position, the ball is pushed above the core and when the core turns to align the ball trap with the pin stack the ball is pushed down by the spring into the trap in the core and remains there.
Some manufactures pre-drill cores with one or more ball trap holes. On other lock products you can purchase a tool for drilling them yourself. When you perform the coding you must understand where the ball trap is otherwise your coded system will be no good.
In the following drawing the construction key is shown in blue and the master key in red.
For this example we will have a master key, a construction key and some change keys with a door each.
In this example we are using a 6 pin cylinder, with a step of 2 (of no importance to the example), depths symbols from 0 to 9 and the construction ball size equal to a step of 4.
|C1||Change key 1|
|C2||Change key 1|
|C3||Change key 1|
The construction ball and trap are in position 3. Notice the construction key code is 4 deeper than the master key in position 3.
|C1||Change key 1||361505|
|C2||Change key 1||361565|
|C3||Change key 1||361585|
There are a number of things that you need to do in PM8 for a construction keyed system.
The construction key designation must be set to Construction.
If you forget to do this when you add the doors, use the PM8
Bulk changefeature to do it super fast.
Here's a snippet of the keying matrix:
When you create the system design and the progression, use the designation "B" for the ball position and be sure to set the depth step for the ball size you use.
In this case, because the key above was set for the construction key and the progression was correct, the automatic coding assigned the construction key code. Otherwise you can enter the construction key code manually or right click on the construction key for options to assign the code to it.
The pinning chart shows the construction ball as "b" followed by the ball size. "b4" in this example.
For most systems, the description above covers all you need to know. Here's a brief note about a few things that you can do for more complex systems.
You can add multiple construction keys in PM8, each operating different doors and usually beneath a sub master for the range of doors operated by the construction key.
It is possible to have multiple construction keys in a single cylinder. This is achieved by having 2 balls stacked in the same position and the second construction key excludes the first construction key then later the master key excludes the second construction key.
|CON1||Construction key 1||369545|
|CON2||Construction key 1||365545|
|C1||Change key 1||361505|
The cylinder assembly in position 3 is: Bottom pin #1, b4, b4, driver pin.
For this to work the core must have 2 ball trap holes.
It is possible to code a system so that the position with the ball is used also for change keys. In this case the construction key cut is the deepest, the master key cut shallower by the ball size and the change key cut shallower than the master key.
|CON||Construction key 1||369545|
|C1||Change key 1||361545|
|C2||Change key 1||363545|
The cylinder assembly in position 3 is: Bottom pin #1, master pin #2, master pin #2, b4, driver pin.
In PM8 you achieve this using a custom progression allowing change keys 1 and 3 (Master key is depth 5 and we do not want to allow depths 7 or 9) in position 3 and add a second progression with only the "B" in position 3 so PM8 knows where the construction keying happens.