Securety: Closing employees only, cant get back in.

Look at the thread from 2002

Or serach google groups for 'alt.locksmithing: "lock+only" owner keys'

Daniel

Thx dbs,

It's nice to come across something that makes you go, "that seems like it should have been obvious to me, and humbles you back to thinking again." Lock work is not an exact science.

mac

I have been doing this kind of thing since the early 80's. I saw an asian import fire safe that had this kind of thing on there safe but they had it so one key would turn to the right only and one to the left only.

Both :-)

regards - Ralph

Charles Courtney described such a lock in his book 'Unlocking Adventure'. It was used on a horse drawn 'paddy wagon' used to transport prisoners from Moscow to somewhere in Siberia. It was locked with one key in Moscow and unlocked with a different key kept at the destination.

My understanding is this is for 360°-turn locks and that if the "master" key is rotated in the locking direction, say 90°, and returned BACK to the neutral position the top pin will contact the side of the bottom pin and prevent the plug from returning to the neutral position. Have I got the right picture? Wouldn't that be a problem if the master key is accidentally turned more than 360°?

Amazing the simple solutions to a problem people can come up with.

Bud--

I've read this trick in locksmith magazines. Dating back many, many decades.

Falcon used a variation of this to determine if a room key for a motel lock would turn only far enough to withdraw the bolt, or if it would turn all the way around. The one which turned all the way around was the emergency key, and would also withdraw the deadbolt. The room key and the maids keys would not withdraw the deadbolt.

This is actually called a Brink Function .... was invented by RR Brink Locking Systems.

BBE had a nice article on it on his TheLockman.com site ...

The Brink Function, Why It Works, How It's Made, November, 2002

.... maybe he will post part of it here ...

Best regards ...

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In article <d0sjcq$aj6$ snipped-for-privacy@news.chatlink.com>, Bud snipped-for-privacy@isp.com wrote: :My understanding is this is for 360°-turn locks and that if the "master" :key is rotated in the locking direction, say 90°, and returned BACK to :the neutral position the top pin will contact the side of the bottom pin :and prevent the plug from returning to the neutral position. Have I got :the right picture? :Wouldn't that be a problem if the master key is accidentally turned more :than 360°?

See if you can picture this. The groove in the plug is narrower than the normal pin diameter. At the bottom of the driver is a turned-down region that will drop into the groove. Below that in the stack is a full-diameter master disc, and below that is a normal bottom pin.

The "lock-only" key has a deep cut that lifts the stack just enough so that the turned-down portion of the driver clears the bottom of the groove. Since the groove is only on one side of the plug, the plug can turn in just one direction. The master key lifts both the driver and the master disc above the shear line, allowing the plug to turn either way. The master disc is too large to fall into the groove, so there is no interference with the lower pins.

Using this method, there will be a range of cuts that lift the driver above the bottom of the groove, but do not raise the master disk above the normal shear line. A key cut like that is likely to become trapped in the cylinder. That could be considered a feature.

IIRC, Abloy offers cylinders with the option of different keys for turning in each direction. That would be a preferable solution.

Actually in real life the Brink Function does not require turning down the end of the top pins. Imagine if you will the geometry involved. A section of a plug through a pin chamber will show how it works best. If the diameter of the plug is altered by two or three depths of cut by removing material on one side of the pin chamber by a cut perpendicular to the pin chamber, that is the only modification needed.

The pin tumbler is wider than the cut depth and therefore will never ride into the side of the pin, it is mechanically impossible. In that way the change key only raises the top of the pin to that modified shear line and only allows the key to turn in one direction while the MK raises it to the plug OD and can turn both directions.

Which side of the p>