A one way cylinder.
This one I actually used on a Liquor Store.
The late night employee was known to lock up the store at closing time,
but sometimes returned and unlocked the store in the middle of the night...
...Apparently, he drank a lot, and when he'd run out, he'd open the store to get more.
Sometimes he would even let his friends come in.
This was a big concern for the owner, here, it is against the law to open the store between certain
hours. This had to stop.
I made a one way cylinder, one key turns to lock and unlock and the other key can only lock. It will not turn the other way.
In the morning, the owner uses his key to unlock the store and at night, the employee uses his to lock up.
Here's how I did it.
Here I took a standard Schlage KIK.
I carefully filed the plug like this.
Then, I took one original key and code cut one with one cut different.
The 2 keys stacked for comparison.
Now, I need to pin the cylider properly for this to work, so look at the chart below.
Top line is how it is pinned and the 2 other lines are the bitting of the 2 keys.
This may seem odd but look closely.
With the clerk's key inserted, you can see that it can only turn clockwise, or to the lock position only.
The cylinder cannot be turned the other way because the top pin won't skip over that step.
Now, the manager must be able to use his key to lock or unlock the store.
Again look closely how the manager's key lift the 3rd pin.
Now it may not seem like this would work well, but it does.
The trick is in the top pin. I used a bottom pin as a top pin but used it upside down
so that the pointy tip can ride over the steps. Of course it's impossible to see this
when assembled so I mocked it for show.
There you have it!
Simple.
It feels a little "clicky" as you turn the key past the shear line but still operates well.
I chose the 3rd chamber but it can be done with any of them and to more than one if desired.
It can be done to 2 chambers and the opposite way. I key can only lock, one key can only unlock and one key
can do both...I don't know what the point would be or where it could be used but eh!
It's fun to do, so, why not?
Have fun making your own!
Always opened for discussion.
M.