Keys and How They Work
For such simple items, keys can get a little tricky sometimes.
The top of the key is called the bow, but sometimes it’s referred to as the head. Many different bow shapes are produced and some manufacturer’s shapes are easily recognizable.
The shaft on a keyblank (uncut key) is where the key cuts are made.
|No Of Pins
Shafts come in various lengths according to the number of pins in the corresponding lock cylinder.
5 pin is for residential locks, 6 pin is for commercial.
The most important aspect of a key is its keyway, or shape when viewed from the edge. This zig zag shape is unique and distiguishes it from all other keyways in the world. Below is a sampling of some keyways from the Corbin Russwin family.
If you look closely, you will see that some shapes are nearly identical to others. The differences are very subtle.
For example, the ”H” group of keyways all carry common features just like parents and their children. It is these common features that allow locksmiths to create master key systems with different levels of access within a building.
Some keyways within the ”H” series are strictly for lower level access such as one single door, while others designed for higher levels such as mangers with access to many doors. These slight differences within a keyway family is what allows for great flexibility when designing a key system.
The peaks and valleys cut into a key shaft are of different heights. It turns out those heights correspond exactly with the length of each bottom pin housed within the cylinder (bottom pins are shown in light blue). The first pin might be a #6 height, the second pin a #8 height, and so on. The idea is to make the tops of the pins all line up horizontally once the key is inserted. And this point of horizontal alignment is called the shear line.
Once all the pins align ”in shear” the key is allowed to turn. Remove the key again and the bottom pins all drop back to the bottom of the cylinder. It can no longer turn because the shear line is blocked by the top pins, as shown in the diagram on the left.