Bumping a lock with a 9 pin??

[Wrenchman]

Thanks ray, that was a very good post, I often have custumors with worn keys, I even have a few padlocks myself with worn keys, with a trick, and if the copied key gets too high, you can just impression the last part!



Wrenchman

[Carrot]

The best solution i have seen is to not drill the chambers through at the top pin diameter that way the top pins at rest are in a counter bore and the smaller bottom pins push up through the counter bore and then lift the pin, if the two pins arent in contact anyway they cant be bounced,

It is after all the transfer of energy that makes bumping possable, the removal of the top pin is just the same as having a gap, if they arent touching they wont transfer the energy,

That's an interesting solution... but I'm wondering if you push up the bottom pins hard enough, will they hit the top pins with enough force to push them up? Kind of like hitting pool/billard balls?

[Shrub]

No because the bottom pins are not the things that jump, they may move a bit but the process of bumping isnt the key pins bouncing off the key its the top pins bouncing off the bottom pins,

If the op and bottom pins can not touch unless the stacks are lifted you would only be able to bump that lock if you had a key cut one cut lower than the real key on each cut and then i imagine it stil wouldnt bounce,

This isnt my solution but one of the better commercial solutions which has been tested against bumping,

[raimundo]

if a long pin is in the plug all the way to the shear, and a bump key is used, won't this pin jump clear out of the plug and the lock open with this pin in the bible?

[Carrot]

I see... I thought that if the bottom pins are not in contact with the top pins, they will not be able to transfer energy (in the manner of Newton's cradle) to the top pins and they themselves will jump instead.

I also read somewhere that with repeated bumping, especially with a plug made of a soft material, the holes in which the pins sit in will get deformed, so i guess that the bottom pins get pushed sideways more than they get pushed up.

As for raimundo, if the bottom pin is long, I guess that the top side of the pin will jump past the shear line and get caught when the plug is turned and the lock will not open.

[Carrot]

I just thought of something to prevent bumping:

You can magnetize the top and bottom pin such that they attract each other when inserted into the plug hole in the correct orientation. Bumping should not work since the pins have such a small mass that the even when the impact energy of the bump key is transmitted by the bottom pin to the top pin, the magnetic force should still hold them together, or at least make them "sticky".

This should also not affect the normal working of the lock since the shear force when turning the plug with the proper key is more than enough to overcome any magnetic force exerted by the pins. Only thing is, the pins may lose their magnetic field over time.

But the good thing is that there is no change to the current lock design, so anyone can just take apart their locks, magnetize the pins and put them back for a bump proof lock!

Hmm... I wonder if anyone thought of this before??

[Shrub]

Its been mentioned and rubbished loads and loads of times im sorry to say,


No where is my brass magnet,

[Carrot]

Sigh... I should have known... should have searched for it before posting... now i'll go see what exactly are it's shortcomings.

[Deathadder]

The first time you rap those magnets, they will lose their strength. I had an idea to prevent bumping earlier, and that was to raise one pin stack out of reach of the key. This would barely limit the keying combinations, and not interfere with the workings of the key either.

[Carrot]

Hmm... yes, but bump keys can just be made one cut higher to reach the pins right?

About impact affecting the magnetic strength of the pins, I believe Prodigy (viewtopic.php?t=12613) said that the pins have to be impacted onto something to make them lose their magnetic strength, just bumping the pins into springs may not affect them much.

cottonmouth also posted in the same topic (viewtopic.php?t=12613&postdays=0&postorder=asc&start=30) that heating the lock to 80-100°C will demagnetize the magnetic pins. This can be easily achieved without destroying the lock. However, I believe that the required temperature to demagnetize a magnet is the annealing temperature of the metal, whereby the "grains" in the metal are randomized and rearranged. For steel, the required temperature is ~400-650°C and the metal needs to be held at this temperature for several hours for diffusion to take place.

However, it is true that magnetic steel pins will have a very weak magnetic force that will decrease dramatically with distance, and may not be enough to hold the pins together against the bumping impact.

[mfschantz]

The first time you rap those magnets, they will lose their strength. I had an idea to prevent bumping earlier, and that was to raise one pin stack out of reach of the key. This would barely limit the keying combinations, and not interfere with the workings of the key either.

I think they refer to that as shallow drilling. They do it to only one of the pin chambers so that the bottom of that pin sits higher than the rest, thus not being touched by the bump key. If you had five pins in the lock and say... seven different lengths, your possible combinations would go from 16800 to 12000 (approximately) if the shallow chamber were two pin lengths shorter than the rest.

[Carrot]

Oops, how do i edit my post?

Anyway i just realized i misunderstood Deathadder's post. Indeed, raising just one pin stack can prevent bumping, thought i imagine that the bump key can still be cut to compensate for that pin if it is known which pin stack is raised or this information can be found through some other means.

[Deathadder]

A) yes, it would be random
B) they're not going to spend 5x the time trying out all the keys
C) if they're criminals, chances are they wont want to learn about that stuff. They just want a fast way in and out