Driver pin at/below shear line

[boroboy41]

I bought an ERA384 replacement cylinder to re-pin for practice and skilling up.

After a little bit of playing with pin 1 only I moved on to pin 2 only...okay so far...when I put in pin 3 only and re-inserted the plug the pins clicked into place but then the plug continued to rotate as I handled the assembled lock which I fully expected to be secured in place and also could be moved in and out of the shell as there was no retaining device at the back. I managed to extract the plug using the key and discovered (apart from minor damage to the spring) the fact that with the key removed the driver pin was at/below the shear line when resting on top of key pin 3.

Is this common for this make of lock?

Any suggestions for getting round this with out chewing up springs?

This is my only lock at the moment as skill level is just above zero

[digital_blue]

If I'm understanding you correctly, you have a pin stack that, when combined, still leaves the driver pin below the shear line, so when the two other pin stacks are picked, and you rotate the plug, the driver pin stays in the plug. Have I got that right?

If so, this is a mistake in pinning. You need a longer driver pin, at least for that pin stack. This is what "balanced pin stacks" is all about. The shorter the key pin (shallow cut), the longer the driver pin you need to compensate. The longer the key pin (deep cut) the shorter the driver pin. This is why a universal pinning kit includes such a variety of driver pins.

Not all manufacturers use balanced drivers. In many cases, there will be only 2 or 3 lengths of driver pins even though there are as many as 9 lengths of key pins. It is really only important to ensure that you don't find yourself in just the position you seem to be in. You can determine this when you're pinning up the lock by dropping a driver pin into the plug on top of the key pin and noting whether it is above or below the shear line. It should be above, otherwise it will be the spring crossing the shear line, not the driver pin, while at rest.

Hope this helps, and after all that, I hope I got your question correct.

db

[Raccoon]

Don't Kwikset, Master and others have only 1 size driver pin?

[pinsetter]

I have seen several locks with only one size of driver pin, but in all instances even with the shortest key pin the top of the driver pin was still a bit above the shear line.

I'm thinking along the lines of DB that when he disassembled the lock maybe a couple of pins came out together and he wasn't exactly sure where they came from, or he just dumped them all out together and wasn't clear on the concept of balanced stacks when re-assembling.

Also, things happen in manufacturing and engineering that sometimes make me wonder if maybe Mickey Mouse was involved somehow. Could be that it was a manufacturing defect, or poor engineering.

I do know that the springs should never enter the plug, and if they do someone along the way had an "Oh Shht" moment.

[Varjeal]

Compensated drivers are rarely if ever used in residential locks. Not sure how it is in the U.k., however.

According to most mfg's every pin stack of every lock should technically have compensated drivers to effectively balance spring tension and locking.

Sounds like the OP may have accidentally swapped a driver for a short/small lower pin, and in the process had one of those special aforementioned moments.

As DB has said, it appears you made a mistake in pinning the lock.

[pinsetter]

To the OP for future reference:

When you pin the lock, after you've installed the pins but before you install the springs, insert a tension tool and apply a small amount of pressure to the plug and make sure it does not turn without the key inserted. Be sure the pins are properly seated when you do this. If you've installed ALL the pin stacks or more than one even, you can take a pen light and look down into the chambers to see that all driver pins are above the shear line. You should never end up with a driver pin that is below the shear line.

Another observation:

I was re-pinning a lock for practice and could have sworn that I done it correctly, when I had indeed dropped the key pin in the number 3 chamber, and then dropped the driver pin in the number 4 chamber by accident.
A quick check with the tension wrench alerted me to the error before I ruined a spring.

[boroboy41]

Thanks for the replies, you're all kinda right.

There was a bit of inexperience and exhuberance on my part and I did just pull the plug and dump the drivers and springs in one go. I did have the foresight to number the key pins before dumping them out of the plug.

The drivers were all one length so I assumed it didn't really matter which one went where and I didn't need to worry about balancing the stacks. I was only using 1 stack at a time in its correct position in the lock to get a feel for what I was doing and so I could use the key to pull the plug again.

I guess its a manufacturing design or fault and this only presents a problem if you're picking the lock pin by pin. If you use the correct key everything is fine. If you use the wrong key stack 3 and/or one of the others will stop the lock from opening. If you rake the lock the chances are stack 3 will bind or set rather than remain below the shear line.

I don't know how you would identify this situation in an assembled/installed lock as a) I don't have the experience and b) I don't have any spare springs to ruin

This also got me thinking that you could maybe incorporate this as an anti-pick feature along with the other standard stuff but that's probably for another thread...

[digital_blue]

It's an interesting thought, but I'm not sure you'd get the heightened security out of it. If one were to pick such a lock and the spring were to get trapped at the shear line, additional tension force you just destroy the spring and turn the plug anyway.

If your lock came pinned like that, it is a poor design, but not altogether surprising.

Cheers!

db

[boroboy41]

Well these were my thoughts on it having read a lot of the subjects in this forum and elsewhere and pondered on it for a few days and nights.

The purpose of the lock on your door is to keep other people out and your stuff in. The reason any would-be-burglar is going to try to pick the lock is to get in quietly but also reasonably quickly. Spools and mushrooms don't stop the lock being picked it only increases the time it takes to pick. The lock is bolted to your door so can't be taken away to be practiced on for a couple of hours a day for 3 weeks until it can be picked in under 5 minutes.

Right, that said how about this setup. 6 pin cylinder, springs at the top, with one of the pin chambers bored out a little more than the others. In this chamber the pin stack sits say 1mm below the shear line, the plug is bored out in this position too but not to the full depth so the key pin can be used to hide the wider bore above. Other pin stacks as normal with as many spools, etc as you like.

Along comes the no-good son-of-a-gun to try and pick it bearing in mind he doesn't know the internal configuration, i.e. binding order, spool positions, short stack position. The slightly wider bore of the short stack should make it the last one to bind so once the other pin positions are set the plug should turn as the spring wont offer any resistance in your short stack. The bottom 1mm of your spring should have enough tightly packed coils to catch effectively on the inside of the plug (most springs I've seen certainly do) so even minimal tension should cause the plug to move enough to damage the spring significantly without it breaking.

Now to DB's point, more tension will overcome the spring. Yes it certainly will but try it and see how much you need to turn it far enough to throw a bolt, the more you turn the harder it gets (more spring trapped, more friction to overcome).

If they manage that and your stuff has gone your consolation is evidence to help settle your insurance claim. If they haven't managed that then the lock has done its job, it might need repairing or replacing but your home has not been violated (unless they rearrange your glazing/door frame/other). You'll also have evidence of attempted burglary so you'll be on your guard.

If you've lost your keys and are locked out...call a good locksmith, if he/she can't pick it either they'll sure as hell will be able to remove and replace (even the bad ones know how to do that, right?)

[Legion303]

It's an interesting thought, but I'm not sure you'd get the heightened security out of it. If one were to pick such a lock and the spring were to get trapped at the shear line, additional tension force you just destroy the spring and turn the plug anyway.

I had a padlock with a spring that did just that, and no amount of tension (with a wrench, anyway) would break it. That spring was a fighter.

I might have been able to break it with something else (key blank, maybe?), but it's hard to tell.

-steve