How to Master Key

[Sinifar]

"Master keying is the controlled destruction of security." Having said that - when one designs a master key system, you should know in advance you will need a common keyed door, or other cross keyed doors. in the keying meeting with the client discuss all they want the keys to do, and where they want them to fit, and where they do not want them to fit. This will become important when choosing the key combinations to be loaded into the system, as you will see later.

You should have at least two and for a system like a small apartment building three pins in common. This will increase the security of the system and lock out random (phantom) keys from the public working. So how many changes do you really need? A computer program will provide at least several dozen pages of key changes, but you only really only need a few dozen to key the job originally, and then maybe a total change of system.

The best way to design a system is to do it by hand. Pencil and paper. It is not hard and only takes a few minutes to work out when you get proficient at it.

Let's start with the most basic part - getting the numbers in some kind of grid so we can work with them. This is called a "MAGIC SQUARE" It looks like this - you choose the odd or even cuts as you feel like working with. There is no rule on this part --

1 0 1 1 0
3 2 3 3 2
5 4 5 5 4
7 6 7 7 6
9 8 9 9 8

Okay, now you have a grid, a magic square of numbers to work from. Start by "X" this is cross off the bittings for the master. So let's choose the master key as 3 6 5 1 4 . Okay, that is your master. Now the change keys. Normally you do not use any cut on the master for the change keys, but we need common cuts, so make the choice where you will use a pin as the common for all the locks.

Going back to what I said earlier, you need common cuts in both to keep out phantom keys, or keys from the public. So for our first common pin we choose the first cut, and make our first common cut say 3. Now every key in the system will have a 3 in the first cut. Now you should have a second cut in common so now let's choose the last cut, 4. Now we have two common cuts in our system, the 3 and the 4. So now you have this set up -- 3 X X X 4, where the "X" in this case is the rotating change keys. Now we work out a load block, the change keys differences.

Looking at the grid, magic square, we get this short list of possible keys.

013 / 015 / 017 / 033 / 035 / 037 / 039 /
213 / 215 / 217 / 233 / 235 / 237 / 239 /
413 / 415 / 417 / 433 / 435 / 437 / 439 /
813 / 815 / 817 / 833 / 835 / 837 / 839 /

819 Exceeds the MACS. So don't go there. You could add another pin to the middle set, say another .030 and get both the 1 and the 3 to work. So your load for this would be either (3 - 5) or (1 - 3 - 5).

This is due to the MACS, mostly a 7 which is the Maximum Adjacent Cut Specification from the manufacturer. You can work out the rest of the load block following my example above. Out of the quick 25, there is a good 12 of them which have a "3" in common. We are getting close to your bitting list of the system. So a common or Maison key would be 3 X 3 X 4, where the "X" this time shows no pins in the pin stack, this is to avoid wafering up the lock which will jamb in time.

So your key list to cut and load looks like this -

30334 / 30354 / 30374 / 30394 /
32334 / 32354 / 32374 / 32394 /
34334 / 34354 / 34374 / 34394 /
38334 / 38354 / 38374 / 38394 /

That will fill the system. For the next one use something else, like 7 and it goes around the same way in the third position. it will give you common keyed locks which are pinned 3 X (3 - 5) X 4. The second set would be 3 X (5 - 7) X 4, or a combined set of both would be 3 X (3 - 5 - 7) X 4.

Select the same way if you need just cross keyed locks, that is key bittings which look like the Maison but are not common to all keys. In this case you would use two like this - 3 8 3 3 4 and the other could be 3 4 3 3 4. This will give you a cross key which is not common as all pins are now filled, but the two have something in common, but different. - 3 - (4 - 6 - 8) - (3 - 5) - (1 - 3) - 4 of course adding the MK for he total load.

For a huge spread, go with 3 X (1 - 5 - 9) X 4, although your number of usable combinations get smaller, it also grows as you added another section to the list. No wafer problem here. Explanation - If you do not like the .030 master pin, then go with something else, like the 1 and you can then use a .060 pin (4) difference. Always remember the MACS. There are way to get more out of a system with a MACS stretcher, which decreases the angle of the ramps or steeples between cuts to 80 degrees, like a Sargent cutter, but that also makes the keys harder to push and pull out. Only do this for the ONE KEY, and make a note on your bitting list that you did this.

Now load the actual cuts into your system by the shotgun method. that is choose your keys between units different so that some goof can't figure his key is 30374 / and the next one down the hall is 30394. Worse - 30334 / 32334. Spread those out as far as possible to keep key jigglers from trying their luck.

Now in a GM system you need more cuts. One way to do this is to add a sixth cut, and make that a master determinator. In this case your original master is 3 X X X 4, where you have the cuts in common, and the X is the rotators. Now add the sixth, and choose anything say 1 3 5 7 9 -- NOW your master could be 3 6 5 1 4, and pick say 7 for this master and 1 for the GM, which makes the GM 3 6 5 1 4 1 and the MK 3 6 5 1 4 7, and the change keys would be say 3 8 3 3 4 7.

Now if you needed to do this is a five pin matrix, then use the last pin. This makes for somewhat secure setting as it is harder to jiggle the last pin. Here from the original MK of 3 6 5 1 4, your GM could be 3 6 5 1 0. This gives you a separation of 4 or .060 between the two masters, not easily manipulated.

NOW here is the final - if you have say two or more apartment buildings to MK, one could be the "3" building and one could be the "7" building. By having this common cut in the middle, each apartment has it's own unique common key which keeps the others in the other building from coming over and using their keys in the others common locks.

By following this basic blueprint, one can make the system as complex as they wish with a bit of planning and thought. Always discuss in advance with the building owner what they exactly want then design it to match. Leave yourself some room for key changes later on.

IF nothing else in a 5 pin system and you are in a corner, and need more than 12 key changes, use the fist as your common and then the last four as the rotators. Again keeping the system tight using say the 3 and 7 in one building and the 1 and 9 in another. This will still give you the basic non wafered up cylinders in the common locks. Remember the MACS and if you need to use the Sargent cutter for those keys only and make a notation on your keying chart that you did that.

Most keying systems we design are 6 pin, but i have done the job in 5 pin and it will work well. Going back to the top where we have a building owner who had several buildings and wants a common GM, then issue the MK for each individual building as shown and you have it done.

Lastly, I used Schlage as the format for this system. Since it is a .015 drop evenly, and a two step constant rotator system gives you the drop of .030 which will not cross. IF you need to go into something like Kwikset you can use another trick - use Kwikset spacing and Schlage depths. There is an HPC card for the 1200 which allows you to do this. Since Kwikset is a single drop of .023, this works out well, and gives you a system which no Kwikset keys will cross. Do not do this unless you have either a HPC 1200 Blitz, and the special card, or a Framon FRA 2 where you can do this manually.

I ALSO have a key cut for my Foley 200 where I can do this, by making a Kwikset spacer key on those spacing specifications and using a 2 for the cut to be worked from. Kwikset 2 and Schlage 2 both are cut to .305 / .306 - a thousandth difference will not make that much of a difference in the end. Trust me on that one.

Sinifar
Member -

Associated Locksmiths of America

[GWiens2001]

Annnnd.... Sticky!

Great write-up, Sinifar. Thank you for compiling your posts from other threads into one easy to find thread.

Gordon

[jeffmoss26]

Excellent post...my head is spinning lol

[Sinifar]

Jeff - it isn't that hard. Print out this set of instructions and follow it as you go along on your own piece of paper.

First make up he grid of numbers like I did, then cross off your master cuts. You should have two common cuts, so to make it easy, I used the middle three. You could use the last three, the first three, or any combination of three you wished.

Now look at your block of numbers.

It starts with "0 - 1 - 1", so your first change key is 3 - 0 - 1 - 1 - 4. The next one is 3 - 0 - 1 - 3 - 4. Just continue the pattern. Remember if 7 which is the MACS fits -- use it. That is the difference between any two cuts cannot exceed 7. Do not exceed the MACS for you will destroy the pin land, that flat at the bottom where the pin sits. So 1 - 8 would work, but 1 - 9 would not. O - 8 would not, nor 0 - 9. But 0 - 7 would.

The more time you spend on this the easier it gets. Just follow along with the instructions and if you get stuck, send me a private message and I will talk you thru it.

Sent from track side on the CN / CP junction at Duplainville.

Sinifar

[jeffmoss26]

Thank you!!

[cledry]

I use this when I only need a small system on the road. Most systems though are much larger so we take advantage of computer programs. We have some large systems that we have to use different key sections in order to maintain a constant. The danger with using different sections is those locksmiths that don't carry a Sargent HJ section for example but will happily take your money and cut the key on a HN. Thanks for compromising a masterkey system. Actually they shouldn't be called locksmiths, I was being kind.

[kwoswalt99-]

Master keying is the controlled destruction of security.

This is my favorite sentence.

[cj101]

Using the key profile for master keying is quite dangerous. For large system, a lock with 6 pins and passive profile pins should used instead.

[cledry]

Using the key profile for master keying is quite dangerous. For large system, a lock with 6 pins and passive profile pins should used instead.

Agreed but I can't think of a US manufacturer that offers any with passive profile pins. Also I have never seen a building in the USA where a locksmith was consulted prior to specifying of the locking hardware. Highrise buildings usually will have a factory system and this is where we inherit the multiple sections from.

[Sinifar]

Master Mills have their place, but this is another story. For Schlage, H - J - K do have an application, but then there is the problem of key duplication. Which is why they go to the odd ball deep into the sectionals area. Not many people have CE, EF, or FG on the shelf, and fewer have the master mills to cover them either. Although I have seen quite a few hardware stores carrying a "L" which is the grand master mill.

If you want to have key security, then you need to invest in something which is not dupicateable. Just using a "do not duplicate" stamp, or a DND key blank is not going to get the job done. From Schlage Primus, any one of them, to Medeco 3, to Assa Abloy Twin, to Mul-T-Lock, will give you some security, but not total.

If any enterprising person has a Keyway King, he can make almost anything out there with no problem. OR if you have a large enough stock of key blanks, someplace deep in the sectionals one can find something which will go into almost anything, and maybe with a slight modification on a Jet 2000.

In the end, it is policing your own system and keeping the duplicates out by having key stock which is unique enough to stand out. Signature keys, those which carry your shop name and phone number stand out, and cannot be had without your knowledge. Using this stock makes the key obvious to any casual observer - and if a duplicate shows up, the holder needs to explain their actions.

Of course having said all that - there are shops which use the "C-K" milled plugs and then run FG keys into them. Now what? Not picking on Schlage, but that is what I normally run into. There are others like Sargent LA - LC milled plugs, as well to cover more systems. Cut the key on a LD? Just some of the fun.

As far as who cuts this stuff - money talks and everything else walks. Find out who is cutting the keys and find a way to get the outfit to quit, or just sell the client something which can't be had easily.

Lately the hardware stores are cutting C123. SO what is the answer? Make new systems in S123. Problem solved. You have to keep up on these things and move accordingly.

Sinifar

[jimu57]

This is first true logic I have found on master keying. Anyone can pin a cylinder with master pins. But for a good approach to design? This is great!!! This is going in my notebook of "great lock stuff".

[C locked]

Master keying is the controlled destruction of security.

This is my favorite sentence.

I second that,
A succinct description

[jimu57]

Returning to this for the upteenth time. In the listing of possible keys showing pin chambers 2, 3 , and 4, the beginning of the list is 013/015/017. Why was 011 omitted? That happened also with 033 being a first bitting.

[RedE]

Returning to this for the upteenth time. In the listing of possible keys showing pin chambers 2, 3 , and 4, the beginning of the list is 013/015/017. Why was 011 omitted? That happened also with 033 being a first bitting.

Jim,

011 and 031 were omitted because they both have one depths in the fourth position, which is the same as the master key (36514). Remember that you only want a change key to share cuts with the master key in chambers that aren't progressed. Otherwise a key cut to 30114 in this example would also operate 30134, 30154, and 30174.

[jimu57]

Thanks RedE. I just read about that. Makes sense. I had been making some matrices on a spreadsheet WITHOUT omitted those pins and was trying to figure how to control out of control situations. Just learned some more today. I'll be back!

jim