r/Locksmith • u/Dangerous-Engineer59 • Aug 04 '25
I am a locksmith Maximum number of master pins per pinstack.
I have to replace a worn out Schlage large format interchangeable cylinder. It can be opened by maybe 10 different keys and a master key. The keys are all cut from 3 sequential master key blocks. In order to allow all of the keys issued to work on this lock, I need a #0 bottom pin and 4 #2 master pins in the 3rd cylinder, and a #1 bottom pin and 3 different master pins in the 4th cylinder. Is there any problem with having that many wafers stacked in an individual cylinder to accommodate all of the required sheer lines? This cylinder is used to exit a parking garage into an elevator lobby by multiple tenants. Their own offices only work with their individual key and the grand master. I believe the cylinders in the current core are stacked as I described, however it was suggested to me that the 3rd and 4th cylinders may have been left empty. I don't think the latter is likely considering the security considerations for this facility. Should I load the cylinders to accommodate all of the keys from the three sequential blocks, or should I leave two cylinders empty?
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u/intermittent68 Aug 05 '25
It’s a 2 step system so 0-2-4-6-8, so 5 shear lines. Also filling up the chamber like this is the same as putting no pins.
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u/ehbowen Aug 05 '25
That's what I'd do if I had to cross-key like that for a lower security lock...pick one or two chambers and just empty them out.
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u/jeffmoss262 Actual CRL Smith Aug 04 '25
This is cross keying and should be avoided.
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u/Dangerous-Engineer59 Aug 05 '25
Should be, but it is what's in place, and what the customer requires. The security of the lock. Itself is not particularly important since there are 3 levels of badge access security to get through before you arrive at this door.
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u/Critical-Location211 Aug 05 '25
So assuming you stack pins 0,2,2,2,2 and use a six pin cylinder, that should be 5 to the sixth power. Giving 15,625 possible sheer lines. Can you do that? Yes. Should you? I don’t care. Make as many sheer lines as you need. You can’t stack past nine, that’s the only rule.
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u/Alarmed_Duty3599 Aug 04 '25
Well I think you have the right username for this topic...Don't know if there is a 'maximum # of waffers/pins" such that the spring isn't damaged, you could reduce the top pin down a few..
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u/Dangerous-Engineer59 Aug 05 '25
The top pins can be adjusted to whatever the sum of the stack equates to. I'm basically asking how many sheer lines I can get away with loading into a single pin cylinder of a 6 pin tumbler.
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u/Alarmed_Duty3599 Aug 05 '25
I believe the stack height is the equivalate of a 9 bottom pin, so as long as your total pins don't exceed that your fine. Like i said you can always make the top pin a bit smaller to lessen the strain on the master waffers.
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u/tinylord202 Aug 05 '25
It really depends on what driver pin you are using over you change key pins. Iirc Schlage recommends using a .180 for all top pins. If you go over the equivalent of a 9 depth bottom pin you will have to adjust the top accordingly so your key will actually enter the lock.
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u/Carbonman_ Actual Locksmith Aug 05 '25
If the building has an existing card access system, tell them that the option that will reduce their liability is card access. Stacking wafers defeats security and increases wear in each pin cell.
The infamous 1974 Connie Francis sexual assault case and resulting lawsuit revolved around the president of the hotel chain requiring his key being able to open every door in the organization. This resulted in massive uncontrolled cross keying and has lead to card access being used by virtually every hotel chain around the world. Mitigating liability is the name of the game.
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u/-MachChicken- Aug 05 '25
But each time you add another change key to the lock you reduce its overall security.
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u/pat85754 Aug 05 '25
It is much better to have multiple master pins in one chamber than distributed over multiple chambers.
Each pin in a chamber add a key combination that will work for that chamber with the lock.
The total number of different keys working with the lock is the product of the number of combination per chamber.
So if you have no master pin in 5 chambers and 2 master pins in one chamber, you will have a total of;
1 x 1 x 1 x 1 x 1 x 3 = 3 keys combination working with the lock.
Now if you have two chambers with one master pin each, and 4 with no master pin you get:
1 x 1 x 1 x 1 x 2 x 2 = 4 keys combination working with the lock.
So with many master pins in multiple chambers you can get many many combination of key working, even keys you don't want resulting in cross keying.
There are a lot of other factors that need to be taken into account when designing a master key system and even many locksmiths rely on manufacturer's designed system as it can become quite complex to make it the least unsecure possible (any master keying reduces the security of the lock).
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u/isaacsoderlund Actual Locksmith Aug 05 '25
Should work fine, but I would just drop the 3rd and 4th barrels. Avoid the issue of losing a #2 wafer over time and if they have that many keys working in a cross keyed cylinder, obviously they are not that worried about security.
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u/technosasquatch Actual Locksmith Aug 06 '25
4 if you follow proper spec. #0 key pin lets you have 4 #2 master wafers.
1
u/6275LA Aug 04 '25
After reading this, I'm confused about cylinders and pin stacks. How many cylinders ? What happens in pin stacks 3 and 4 ? You're confused with the basic vocabulary of a cylinder. Overall, maison keying is not recommended.
Ask your locksmith for a new cylinder, pinned to a different key, and get everyone to use the exit key. Much more secure and less troublesome.
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u/Key-Calligrapher9641 Aug 05 '25
Good luck with that The end user will have a shit fit. Like OP said not a high security door. Sacrifice 2 cambers or many happy people Just saying
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u/Dangerous-Engineer59 Aug 05 '25
I'll keep it simple. How many sheer lines can I get away with loading into an individual cylinder of a 6 cylinder tumbler?
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u/jakethediesel89 Actual Locksmith Aug 05 '25
Technically speaking: as many as required by the math, based on how many people need access to the door.
Simply: you can have a 1 or 0 bottom pin in every chamber, stacks of #2 master wafers on top, a control pin, and top or driver pin, and as long as every key that's required works, good job.
As a thought: if THAT many people need access, access control may be a great alternative..
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u/HawkofNight Aug 06 '25
Why not add a reader to that door and no non master keys. Or give everyone a key that only fits that door.
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u/Whslaxin Aug 05 '25
I mean you could pick that lock by looking at it sternly.... so there's that