Tolerances - Loose, tight, and in between.

[PoP Lock PoP Bottles]

I realize that there is no such thing as a perfectly tight tolerance due to the fact that the drill bit wears down a little bit each a hole a drilled. Even that being granted what is generally considered tight tolerance? I mean what are the general differences is order for a tolerance to be "tight" versus "loose". Also what type of tension is used to get around both types?

[Zheol]

type of tension is used to get around both types?

the tension is diffrent for all locks as i'm learning you just gotta feel it out


Z.

[Olson Burry]

I suppose generally you can tell the difference between tight and loose tolerances by resetting the plug and seeing how many degrees of movement you get before the first pin binds or generally how much movement you can get out of the plug before starting to pick it. Also in a lock without security pins, the amount of movement you get whilst setting the pins one by one would be an indication of how sloppy the thing has been made.

Tension would be worked out on a lock by lock basis as stated by Zheol and there are probing techniques. Generally I prefer very light tension but then you have to be careful how you move the pick in the lock and apply pressure to the pins so you don't change the bias being applied with the wrench. So it would also depend somewhat on how practised and refined your technique is

You could lift all the pins with the back of a pick and then apply fairly heavy tension and then slowly release it, when you hear the last pin drop, a little more tension than that would be around the bare minimum to start. Or find the binding pin and see how little you can apply to get it set. (sometimes using the method above reveals the binding pin quite easily).

Feeling the difference in all the pins with and without tension will also let you get more of a feeling about the lock.

[Jaakko]

If really talking about tolerances, I'll give you an example. If a hole and the pin has a gap of 0.01-0.02 mm (the hole can be also smaller than the pin), it is a fit that requires heating the hole and it doesn't pull apart. If it has a gap of 0.03-0.06 mm, it is a ram fit, meaning that you can get the pin in the hole by wacking it with a hammer or by pressing it in, but it won't move on its own. If you have a gap of 0.07-0.10 mm, it is called a sliding fit, meaning that the pin moves in the hole.

[zeke79]

On locks, a "tight tolerance" would be +.000" and -.003". This means that your key can be cut no shallower than specs indicate but will function with the key being cut at up to .003" too deep. Tolerances are made this way to allow for key and pin wear while offering the best tolerances you can usually achieve while still offering a lock that will function well and have a good service life. The above posted are the tolerances for some ASSA locks. The plug to shell fit is so tight that being .001" to shallow on a cut will leave a pin protruding enough from the plug to cause both wear on the pin and shell and also leave you with a tight turning key.

Alot of factors must play into a manufacturer's design tolerances. They must take into account that the lock may be installed on a black colored exterior door on the west side of a building in 100-110+ degree temperatures in the shade. On top of this, the heat absorbing black color of the door plus the radiating heat from blacktop and concrete etc in an area like Las Vegas would require the above posted tolerances to end up with a lock that functions well in both high heat and very cold conditions.