Manufacturing tolerance

[Jaakko]

There are five errors that one hole can have:

1. Size
2. Location
3. Shape
4. Angle
5. Surface quality

You will never ever get two exactly the same holes, so that is what tolerance is about: To allow for the small changes and still work.

[Bertrand]

Wouldn't you just be able to pick it in any order, since ever pin would bind?

[barbarian]

I read a book a while ago about the development of jet aircraft after the war. The designs required things like bearings that were very precise. The technology of the day could not produce them reliably. So what they did was add a measuring and sorting station to the production line of regular bearings. They would check all the parts as they went by and they would find that one in ten thousand that was "perfect" for the application. The parts would be saved until they had enough for a complete bearing and then it would be assembled.

After days or months of production there would be enough "perfect" bearings.

I think modern lock manufactures could use a system like this if they wanted a super accurate lock for some reason. There would be little extra cost involved. But would there be any significant benefit ?

[lockeymoto]

Interesting concept, the "perfect lock"
It would make bumping super easy for kids
The imperfections do get multiplied in cheap locks and these do get worse as they are used, some you could open with a Popsicle stick!!

[unjust]

the other issue is that assuming you have zero slop in the pins you still need to have clearance between the pin and its hole, which will give you some latitude, and there will always have to be some clearance between the top and driver pins at the edge, at a minimum a little more than the clearance necessary for the plug to turn within it's mount, which will give you the necessary edge to catch at least one pin on.

in order to achieve the tolerances necessary to remove any slop, you've also removed any movement in the mechanism. as long as the pins and plug can rotate (unless we're looking at something like a sealed bushing, which introduces all sorts of access issues) there must be *some* slop within the system. of course the more precise the mechanism is, not only the harder it is to find that leeway, but the more reliable the system is, in that you're not counting on two gross tolerances aligning accurately, you're counting on fine tolerances aligning.