Any locks with a plug like this?

[SnowyBoy]

Was just thinking, are there any pin tumbler locks on the market with holes drilled into the plug like i'm showing in this picture?

http://img461.imageshack.us/img461/7037 ... opydk6.jpg

Was just sitting here thinking about it.

[SnowyBoy]

Ok, stupidly i've just noticed that if it WAS like that, even with the key in the barrel would lock lol

So yeah, what if you had a V shaped key so that when the plug turns past the other part of the key, the pins don't fall down. Yet if you pick it, once turned the pins would drop down and need to picked again.

[nothumbs]

You would need a second set of pins in the second holes in the 'barrel', else the top pins would drop into the second set of holes. The bitting could be different for the second set.

[SnowyBoy]

Ah yeah. What about a tapered skirt at the top of the pin to hold it in the plug? To stop it falling through into the keyway?

[Eyes_Only]

I think those holes off to the side is for construction master keying. If I remember correctly they use ball bearings for it and when the home owners key is used the bearings fall into the holes making the construction key useless.

[raimundo]

actually, holes in the plug, without a keyway beneath them would work like a 'dynamite bolt' relocker on a safe, if picked, and in the case of the illustration even with the key, this will turn only a fraction and then become permanently stuck when the top pins go into that blind hole.

[MacGyver101]

If I remember correctly they use ball bearings for it and when the home owners key is used the bearings fall into the holes making the construction key useless.

That's exactly right. Locks constructed like that have a set of ball bearings inserted between the pins and drivers. The "construction" key has shallower cuts which keep the ball bearings inside the cylinder. The "home owner" key (used when construction of the house is finally done) has higher cuts which force the ball bearings above the shear line; the first time the cylinder is turned with the "home owner" key in it, the ball bearings drop down into holes in the cylinder which look very similar to the ones that SnowyBoy is envisioning... this prevents the "construction" key from ever being used again, but has no effect on the "home owner" key. You can think of it as a sort of one-time-use "master key" system.

[MacGyver101]

I should have mentioned... in the "construction key" systems I've seen, the ball bearings (and corresponding secondary holes in the cylinder) are somewhat smaller than the normal driver pins: this eliminates the need to have a ball bearing in every pin stack.

[SnowyBoy]

Thanks for the explanation MacGyver, very insightful.

anyone had one of these locks dismantled to see the componant parts & workings of?

One thing i am baffled by.....do you have to use the owner key before every use of the construction key?

[MacGyver101]

One thing i am baffled by.....do you have to use the owner key before every use of the construction key?

No: it's sort of like a master key system... when the cylinder is first manufactured, either key will work. (The construction key keeps the ball bearings below the shear line, and the owner key keeps the ball bearings above the shear line... but the cylinder will turn either way.) The difference between this system and a proper "master key" system is that the ball bearings disappear (well, they drop into the extra holes in the cylinder) the first time the owner key is used... and without the ball bearings there, the construction key will never work again (because it will lift the remaining pins to the wrong height).

It's much easier to understand with a picture... sadly, I haven't seen a clear one posted anywhere.

Hope that helps...

[SnowyBoy]

I think i can see how it works........but like you said, a picture would say a thousand words

Anyone?

[MacGyver101]

Hrm... okay... this is probably close enough. If you go to the Google Patent Search:

http://www.google.com/patents

you can search for patent 3,183,692 (just type in "3183692" and select the first link, and then click on the drawings). This particular design is backwards to the designs I've previously seen... in these drawings, the construction key pushes the ball bearing up above the shear line, and the "owner" key allows the ball bearing to stay in the cylinder (and the ball bearing is ultimately deposited into the hull, rather than into holes in the cylinder)... but I'm sure you can get the basic idea of how it works.

I can see at least one fairly significant security problem with the design shown in the patent... but it's not appropriate for discussion in the open forums. Suffice to say, I think there's a good reason why most of the "ball bearing" designs work as discussed earlier in the thread.

[SnowyBoy]

I think i can see the same problem as you. Something about the ball bearings and their resistance to the shear line i presume?

Like you said though, not open for discussion in this forum.

[MacGyver101]

. . . Something about the ball bearings and their resistance to the shear line i presume?

That, and the ability to reactivate the construction key under certain circumstances.

[SnowyBoy]

God i'm dying to discuss this you know lol