Keys and shape..

[Jow]

After looking at a number of keys for pin tumblers i've begun to notice that there is a pattern emerging that i cant work out. Basically every where there is a 'flat spot' where the key pin is meant to sit there seems to be a lump before it. These lumps range from big to very very small but are there none the less. This may just be an Australian thing as i havent seen over-seas keys.

the only thing i can come up with is that it may be to work the driver pin over the sheer line a little in order to make sure it passes the breaking point or to ensure it hits the sheer line? im not convinced... or perhaps there there mainly to make the key look more complicated than it actually is to give an impression of extra safty to the owner??

any one know why??

[WhiteHat]

if I'm understanding you correctly, those "lumps" are just extra bits of metal that are left behind by the key cutting machine only cutting where necessary.

they will likely wear away on your key after prolonged use and do not directly contribute to the key opening the lock.

in most pin tumbler locks the pins only need to be lifted to the shearline, nothing more.

[Jow]

not exactly.... ill try to get an image up.

[Jow]

[Jow]

[WhiteHat]

yep - that's all you need - it's just that the key cutting machines don't cut away that extra metal - they just cut down to where the pins sit.

if you get a copy made and file away the bumps your key should still work.

[MrB]

I think perhaps the hollows where the pins rest help to retain the key firmly in the lock when it is turned? Without the "bumps" the key would be able to slide back and forth a bit, perhaps bending the pins in the hands of clumsy users, and with some bitings the key might even come clean out. At the very least it would not feel right if there was some in-and-out play in the key while turning it.

[logosys]

I think perhaps the hollows where the pins rest help to retain the key firmly in the lock when it is turned? Without the "bumps" the key would be able to slide back and forth a bit, perhaps bending the pins in the hands of clumsy users, and with some bitings the key might even come clean out. At the very least it would not feel right if there was some in-and-out play in the key while turning it.

They are actually there to make sure the key cannot be removed while the plug is turned.

[Biksit]

Logosys is quite right. I've done this on my own keys for my shed, as it's a lot smoother entry and exit. (And just to prove to a disbeliever that it would still work!) If the depth of each cut increases as you move away from the key bow, it will be possible to withdraw the key at any position.

[mbell]

A number of standard double wafer car keys do not have the 'lumps'.

I don't know if there's any genuine reason not to have them. The only things I can think of is the manufacturing process making the keys is different or it might be the same as having rubber/plastic headed car keys - to reduce injury if they manage to fall out of the lock during a crash or whatever.

[thertel]

I'm gonna point out something I think may have been over looked. While they may contribute to keeping the key in the lock while rotating, thats just a side effect. Think about this, Will a key with a single low high pinning be able to be pulled out? No, because the pins cant move past the bitting. Look at the key he pictured if you tried to pull that out of a lock with descent tolerances it would not come out, due to the last 2 cuts.

Thomas

[logosys]

I'm gonna point out something I think may have been over looked. While they may contribute to keeping the key in the lock while rotating, thats just a side effect. Think about this, Will a key with a single low high pinning be able to be pulled out? No, because the pins cant move past the bitting. Look at the key he pictured if you tried to pull that out of a lock with descent tolerances it would not come out, due to the last 2 cuts.

Thomas

Keep in mind also that saying "all keys must have a hi-lo-hi combination in them somewhere would limit the number of key combinations possible. Thanks to ANSI standards, there must be a certain number of combinations possible. With only 5 pins to deal with, you're even further limited. The reason that the double wafer car locks dont need the lumps is because they generally have 10+ wafers, and can afford to put the hi-lo-hi restriction on themselves.

[thertel]

I wasn't saying that all locks did but I have about 50 University of Texas keys sitting in front of me, and every last one has at least one cut that would prevent key removal. I'm just looking at everykey I have and every one of them also has a bitting that would prevent key removal. I'm not saying that all of them will, but I brought this up because I believe the lumps are just side effects of the keycutting, not to mention it makes the key look more secure. The flat key just doesn't appear to be for as effective a lock as the lumpy one. Just my opinion though.

Thomas