if the lock...

[Fogmeister]

Yeah, that's correct.

And, yes, it does work for any number of chambers inside the lock.

Basically, if you want to have a single lock that can be opened by lots of different keys then spread the pins round different chambers.

(Just trying to think why you would want to do this though, it would make them a doddle to pick)

[skold]

P.S. Yes, to all you smart people I know that locks 10-12 are unsafe for use as they can be cut down to operate as masters, this is just an example.

what he means, for the people who are new to master keying,
the master key has cuts 495610

the individual keys in question (10-12) have the cuts higher than the master, and can be cut down to have the same cuts as the master key.

i.e.
495610 - Master
495010 - Key 10
495210 - Key 11
495410 - Key 12

So basically, the 4th cut of the individual keys can be cut down from their cut (0/2/4) to the master key cut of 6. Which is something you should make sure cannot happen.


And that's just ONE of the things you have to keep in mind about master key systems. Wait untill we get into phantom keys...

And for 10 points, can someone tell me why keys with cuts only 1 cut different are bad? (i.e. 495610 and 495710)

Speaking of Phantom/Ghost keys.

I had to recently extend a MK system for a customer. I had been given the list of keys that where in use and their cuts. I guess the locksmith was fairly stoned when he designed it because there where atleast 12 phantom keys.

[p1ckf1sh]

Hmm... that's true.

Give me a couple of hours and I'll get you a proper equation.

Good to know I wasn't totally off-beat. I was figuring I kinda missed something totally obvious to anyone else but me...

Thanks for the input further down the thread. It is amazing how much math one can put into something like locks...and I always hated math.

[p1ckf1sh]

OK, I got a formula but it isn't a very tidy one.

Basically the number of keys can be worked out by multiplying the number of pins in each chanber (is that the correct word).
2 - 4+1 - 6 = 1*2*1 = 2 keys
2+1 - 4+1+1 - 6+1 = 2*3*2 = 12 keys

Just nitpicking here, but you're not multiplying the number of pins in each chamber here. You are multiplying the ("number of pins in each chamber"-1) because only the pin in the keyway and the extra master pins count.

SCNR

[Fogmeister]

OK, I got a formula but it isn't a very tidy one.

Basically the number of keys can be worked out by multiplying the number of pins in each chanber (is that the correct word).
2 - 4+1 - 6 = 1*2*1 = 2 keys
2+1 - 4+1+1 - 6+1 = 2*3*2 = 12 keys

Just nitpicking here, but you're not multiplying the number of pins in each chamber here. You are multiplying the ("number of pins in each chamber"-1) because only the pin in the keyway and the extra master pins count.

SCNR

You know what I meant!

But yes, you are right.

[p1ckf1sh]

Ah...I hadn't thought of that (bad idea, anyways, isn't it ?) But I went over the math and this is correct (and works globally):
[...]
Please let me know if I've made another mistake!

I don't think so. But your remark "bad idea", is that related to the concept of spreading masterkey discs over multiple chambers? It might be a bad idea, but at least around here in Germany it is employed very often in apartment houses.

Here you need a system that allows only one key bitting to open the individual apartment door (master keys for the owner or proprietor are not legal, as no insurance company would insure burglary if an "outsider" has a key). But there are usually lots of doors/locks that require to be operated by anyone, such as the main entrance, basement doors, doors to utility rooms, etc. For added convenience (who wants to fiddle around with so many keys) you usually have one key that opens all those doors plus the individual apartment door, therefore the "public" locks are often setup like this.

I think so at least, never took apart a lock from a door like this. But considering an apartment complex with 40 apartments, you are absolutely forced to spread the masterkey dics over 2 or even three chambers to accomodate for the number of keys that should open the lock. Even with only like 10 apartments, it would be better to spread the setup over two chambers, because we have seen that it is mathematically more sound solution. You could put all these discs into one chamber (there are quite some manufacturers in Germany that have more than 12 bitting depths) but that would require 9 discs. Spread it over 3 chambers and you get away with using only 5 discs (3*3*2=12 possible keys)...

And yes, these are easy to open. I can rake the main entrance door of my place (which has only 12 apartments and a 6pin lock) in seconds with my pocketknife bogota. To the casual observer it might look like I am using a key with both of my hands.

Enough rambling...

[datagram]

Well, its a bad idea because of the added potential problems with masterkeys/phantom keys/and that it is easier to pick the lock with so many added shearline possibilities.

[Mr. Lock Pick]

i dont understand the illustration