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Been looking more at A2 systems trying to understand their makeup better. Have not seen the answer to my question printed in any of the literature I have found, so thought it would be good to ask here. If I understand it correctly, you do not want the master pin and the control pin combined to equal 10, because then the change key (at least for that pin stack) would equal the control key bitting. Is this correct?

Gordon

Not necessarily. It's perfectly fine to use a couple of #10 buildup pins. What you shouldn't want is to have to use a #10 buildup pin in most (all but one) of the chambers. Using them in all but one chamber could possibly be a security vulnerability because of how much easier it is to pick, or figure out the control key.

Also, if all of the chambers use a #10 buildup pin, then the control key probably won't pull in the control lug. So at least one of the chambers can't be using a #10 for the lock to function properly.

Think about it this way, the buildup pins should be completely random. Just like when you look at a key, the cuts should be random. Having an SFIC with all but one buildup pin being a #10 is akin to having a house lock pinned to 00030. Is it functional, yes. Is it easy to decode or rake open, yes. I know that the SFIC should still have a key that has completely random cuts, so it's not exactly like my house lock example. But when you compare the control key to the change key, and a key blank to my house lock example...

"you do not want the master pin and the control pin combined to equal 10, because then the change key (at least for that pin stack) would equal the control key bitting. "
Why is that?
True that I don't really get these SFIC-s so explain it to me as I were 5.
I know Gordon, you 5 years old kid could explain it to me

Google sfic schlage service manual pdf ,good stuff

I am NOT a locksmith, just a hobbiest, so take my post with a grain of salt. The pin depth steps (on an A2 system) are .0125". Rather than having to do the math for each depth, they made it much easier by just calling the pins by their number rather than by their depth. A #1 is .0125", a #2 is .0250". #3 is .0375", and so forth.

The difference between the plug shear line and the control shear line is .125", or 10 steps. Since there are only 10 bitting depths on a Best (or Falcon, etcetera) key, this is intended to keep someone from making a change key by simply increasing or reducing the cuts of the key by 10 steps.

Ideally, in a Best A2 system, each stack should add up to 23.

Gordon

P.S. As of two days ago, he is 9. But it seems like only yesterday he was 5. And no, this is waaaay over his head. It is only not over my head because I stand up on my tippy toes and stretch my mouth up high enough to breathe.

Hahaha

I should Probably mention that from a lock picking perspective. SFIC are difficult to pick because there are two shear lines and it can be difficult to set all the pins on one shear line. But everytime a #10 is used the second shear line is removed from the equation for that chamber. Which is why it makes it easier and easier to pick when more and more #10 buildup pins are used.