Raise your hand if you have the "anti lock-bumping"

Trope · Post by **Trope** » Wed Mar 21, 2007 8:09 pm

I wonder if an extra pin, maybe .050", on top of the driver (top) pins would help. What I'm thinking is that the new pin would jump up, but that wouldn't matter because the driver pin would not jump up, and would remain across the shear line.

Are there any locksmiths here who have tried this?

jimlongley · Post by **jimlongley** » Wed Mar 21, 2007 9:15 pm

Double pin locks are quite common.

If you look at the pic in the wikipedia site, you will see the pins split to correspond with the cut of the key.

Now picture a second pin above the first. If those pins are all the same height, then you have a lock that a second key fits, and all the notches, if any, are all the same height.

It's called a master key, and that one would be a pretty poor one.

Actually, locks that are keyed for masters are usually set up so that the master has less depth to the notches so that you cannot take a regular key from the master set and cut it down to make a master.

From Wikipedia: A master key is designed to open a set of several locks. These locks also have keys which are specific to each one (the change key) and cannot open any of the others in the set. Locks which have master keys have a second set of the mechanism used to open them which is identical to all of the others in the set of locks. For example, master keyed pin tumbler locks will have two shear points at each pin position, one for the change key and one for the master key. A far more secure (and more expensive) system has two cylinders in each lock, one for the change key and one for the master key.

Larger organizations, with more complex "grandmaster key" systems, may have several masterkey systems where the top level grandmaster key works in all of the locks in the system.

Trope · Post by **Trope** » Fri Mar 23, 2007 9:12 pm

I'm not talking about a master key, with a double shear line. In my scenario, the top pin would be small, and would not create a second shear line. Since it sits above the top pin, it would still be above the cylinder, against the spring.

jimlongley · Post by **jimlongley** » Fri Mar 23, 2007 11:04 pm

To avoid creating another shear line, the extra pin would have to reside entirely above the shear area and even so, both or all pins in any stack are going to move up in response to the bump, one of Newton's laws.

Now if you could come up with a mechanism similar to the Browning short recoil system, that might work, but I think the locks would be both impossibly complex and prohibitively expensive.