What length Top Pins should I use when repinning lock?

[Squelchtone]

Hi,
May someone please explain to me when to change a top pin during rekeying. I see this chart here and it says that the top pin for say a 7 is a .165. If I install a 5 should I have to change the top pin to a .200?

http://www.mrlock.com/categories/pin_lengths.html

Any help is really appreciated. Thanks!

[Squelchtone]

Hi and thanks for your question.

The main reason there are different length top pins is to help balance the pins stacks in the lock so the key inserts smoothly with equal spring pressure across the whole lock, this also helps with even wear over the life of the pins and cylinder.

I would say that most people use a plug follower to trap the existing top pins and old springs up in the bible, and only dump out the key pins and repin a lock leaving the top pins and springs that were already there for the old key combination, this is the quick way, but may not be the right thing to do since if a 3 cut is suddenly a 9 cut on the new key, the key may not work smoothly, the pin stack may not be high enough to keep the spring out of the plug (someone please verify this, I'm speculating), the spring may become too compressed and stop performing it's job in a pin stack that is too tall, or some other reliability issue may present itself.

If you know how to take a lock apart and you have a pin kit with the proper top pin lengths available to you, I'd say go all the way and repin it to spec.

Hope this helps,
Squelchtone

[spike2013]

Thanks very much for your answer, it confirms what my thought was.

Best Regards!

[cledry]

The correct way is to use short top pins with long bottom pins and vice versa. Most of the time as has been mentioned this isn't done and usually no cause for concern in a regular lock. When master keying a lock though it can cause problems, you end up with a too tall stack height and you cannot insert either key into the lock to remedy the problem. What I do in this case is cut a key to all the deepest combination of the two keys, I also blend the cuts so that all the peaks are removed between the cuts. Often this will enter in order to remove the plug, pins and springs and correct the situation.

[fgarci03]

@Spike: Thank you for bringing this up. Never thought about it and Squelchtone's and Cledry's responses make so much sense.

Always learning