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Discussion on master keyed locks and bumping

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#1 brad22482


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Posted 22 February 2007 - 07:20 AM

I got to thinking about the physics of bumping and was wondering if anyone knows if a bumpkey will work on a cylinder for a master keyed system (ie. a cylinder with 2 or more top pins and 2 or more shear lines)?
I dont believe it should as only the uppermost pin would move and that is most likely not going to make a shear line. Does anyone have any experience with bumping master keyed systems?

#2 BLK


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Posted 22 February 2007 - 09:18 AM

I bump master keyed locks all the time. When the property management company that I work for gets a new property, I usually have to rekey and master that property. Most of the time we do not get keys to the new property so I get to compromise the lock. If it is still mastered from the builder, it will bump. When I master it to our system, it will bump. The physics of the bump: the top pin is going to get bumped above the shear line so the plug can turn. That is how it works.
Bump it to the next level.

#3 theopratr


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Posted 22 February 2007 - 12:41 PM

The corollary to which is that master pin itself is generally extremely small in relation to the other pins. If you want to talk physics, the energy is transferred through the bottom pin to the master and top pins. The top pin, obviously being last in line, gets the bulk of the energy, throwing it well above the shear line, but the master pin, of relatively small mass, gets thrown to a decent height considering it only got "lost" energy that was not efficiently transferred to the top pin. Master pin systems have only one shear line, although one or more of the sets of pins breaks at more than one point.

If you get into interchangeable core systems, like BEST for example, you actually have two shear lines, and thus bumping becomes much harder. It takes a lot of practice to open those suckers. And then a master keyed interchangeable core... that's a bad day.

Again, not impossible, but it usually results in a very fine mess.

#4 ChicagoLocks


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Posted 02 April 2011 - 12:34 AM

Last year I bumped master keyed system. I am not sure whether it works all the time but I tried three times and It worked for me. I used the same method as described above that top pin above the shear line.