Strange but true (self bumping lock)

[Tattoo Guy]

Was called by a customer whom I had done a job for in sept 04. At the time they could not operate the lock from the out side of there french doors, when I got there the cylinder was turned 180 degrees, the only explanation I had for this was someone had tried picking the lock, got half way and couldnt finish it off , this seemed plausible as they told me a friend had been messing with it to try and sort it out for them ,I reset the lock and they were happy.
Anyway I was called back yesterday as the mechanism had failed but when I got there the lady told me the lock had also stopped working from the outside again , once I had opened the doors I had a look at the cylinder and Yes once again it had turned 180 degrees, I couldn't give them a reason for this other than the cuts on the key where all quite shallow and the lock had bumped itself open when the door was slammed ,rotated through 180 degrees with the vibrations of the door slamming and jammed up when the pins had gone into the keyway.

Has anybody ever come across a self bumping lock before , I asked the customer if I could take the lock and key to have a play with so Im going to have a mess around with it at some point see if I can bump it without a key.

[wtf|pickproof?]

Hmmm, that sounds scary to me.... Get the poor lady a proper lock.

[horsefeathers]

Are you sure the cuts on the key were all very shallow? Bump keys use the deepest cuts.

Perhaps it has no top pins and springs (lord knows how) ......what did you find when you took it apart?

regards

[gazzaull25]

hi ive also seen this happen in my area too also on french doors but it happened on the inside so rules out picking unless the customer was having a play

ive also seen it on a back back door as well cuostomer not able to insert key?? but reset the lock and she was happy not sure what was causing this but would be nice to hear if any body finds out!!

one thing i did notice that both times they was both upvc

[quacking_duck]

Is it possible that the cylinder was of poor quality and used a key with deep cuts at the tip, the cuts on the key gradually getting shallower and shallower towards the bow?

If so, as the pins nearest the cam would be the longest, this may allow the key to retract at another point other than a 360 degree turn as each of the 5 (or 6) movements of the key on the pins, in retraction, may, in theory, allow the next key cut to move one pin further forward each time without pushing the next pin into the plug housing in an incorrect plug position (poor tolerance, badly cut keys, worn pin etc..) I've had a similar problem with a worn rim, except the backset spring on the rims may still push the plug back to the correct place unlike a Euro on UPVC.

The customer could possibly have been able to remove a key like this on the outside, then when it has been used from the inside, the cam may have picked up the partially turned plug on the adjacent cylinder and jammed its drivers in the keyway at 180 or the plug could have moved and stuck there if door was slammed shut.

Only a thought.

Q.D.

[Varjeal]

I actually had a situation like this recently, and after a few minutes of thinking figured out what happened.....

It was on a store on their front door. The key had been pulled out of the lock in the 180 degree position. When I looked at the key itself it was very worn (as was the mortise cylinder.) The cuts on the key were extremely shallow save for the tip one which was slightly (not much deeper)

What happens is that due to the manufacturing process, some types of mortise cylinders have a dentent at the 180 degree position. If the lock has all very short bottom pins, the pins will fall into this groove slightly, allowing the key to be pulled out. The customer then cannot reinsert their key because the top pins fall into the "bottom" groove of the plug, locking it slightly. This will leave the cylinder looking like someone has attempted to pick it and left it in that position.

The solution of course, is to stick the flat side of a pick into the 0 degree position, lift the top pins out of the way and continue to rotate the cylinder. I would generally advise a complete replacement of the cylinder, and of course a repinning to a different configuration with at least two deeper cuts in the bitting.

[Chrispy]

Solved.