by Sinifar » 17 Jul 2013 7:26
How far does a key have to be off? That depends. Mostly they should be about + or - .002 or so. Mostly closer. this is how pin kits work. You CAN get away with being off somewhat due to the "radius arc" of the barrel. That is the thing has to turn off center, and it will work if you are off a bit. Which is why .005 pins work. They are not really close to a lot of manufacturers pins sizes, like Corbin - Russwin / Emhart. Also Arrow and Sargent are off with .005 pins. This is why .003 pins were developed. Although they still are off a bit, but much closer.
However, home, read that retail locks can work up to -.010 some more. Like Weiser. That will work out .015.
Spacing is critical. If your spacing is off, then the pin rests on either the opening or closing ramp. That is the "steeple" between cuts. This will also throw the thing off.
ALSO many deep cuts cause the key to ride up as the cutter draws the key blank in, thus ruining the key. I have seen recently a Sargent key where the first two cuts should have been 7 - 8 - 4 - x - x and it gauged out to 8 - 9 - 4.5 - x - x towards the the next one down. The " x - x' cuts were dead on and high. In a .020 system this means the cuts were ,010 off, and worse this was a master key, sectional. Try to pin new cylinders with this! Nightmares.
Just for your reference - Kwikset - Shoulder to first cut - .247 / between cuts .150 // Titan shoulder to first .097, spacing between .150 // Cuts - 1 - .329 / 2 - .306 / 3 - .283 / 4 - .260 / 5 - .237 / 6 - .214 and 7 we don't talk about because it not seen in retail locks, it is used for MK work only.
Schlage - Shoulder to first cut - .231 / between cuts .156 / Cuts - 0 - .335 / 1 - .320 / 2 - .305 / 3 - .290 / 4 - .275 / 5 - .260 / 6 - .245 / 7 - .230 / 8 - .215 / 9 - .200
Just for giggles - Sargent Sectional - .020 Increments - Shoulder to first .216 / between cuts - .156 / Cuts - 1 - .328 / 2 - .308 / 3 - .288 / 4 - .268 / 5 - .248 / 6 - .228 / 7 - .208 / 8 - .188 / 9 - .168 / 0 - .148 / and X is the same as "0".
A dial caliper is the handiest thing in the shop when working with worn keys. You can mike up the cuts and then add from there to get the next one up which usually will fix the problem. However, if the key is like the one I mentioned above, you need to catch the fact that the key rode up when it was being cut, and the first few cuts are off, due to the key blank being drawn into the cutter. One solution is to put a piece of folded paper under the pattern key and build it up a few thousands, then cut the new key from the "built up key". This has been the solution for ages for worn out keys.
With "laser cut keys" without steeples, you are on your own. They will work being off. Just the cuts need to be somewhat dead on.
Solution - ALWAYS tighten the key in securely. If you want to gauge how tight, you should not be able to pull the key out of the holding vise.
Just my experience.
Sinifar
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