View Full Version : OT Duplicate keys

07-15-2012, 01:54 PM
I guess it's a pet peev, but I have one of my original house keys. I don't have to jiggle it, just stick it in, turn it and presto the door opens. My wife gave her original key to one of the kids years ago and has since had numerous duplicates made at various places, but mostly W-mart. Every key has to be jiggled to open the door.

I wanted a duplicate to put on a seperate key ring with a new set of truck keys so I didn't have to lug around 20+ keys. I decided I would take my original key and go to Lowes and have one made, (already told her I didn't like the machine at W-mart.) She also wanted a copy with one of the Pooh Bear characters. Guess what? Both stinking keys have to be jiggled, and seem to be worse than others she's had made from a duplicate.

What the heck, can't anyone make a duplicate that you don't look like your breaking into a house with a lock pick?

Do you think it would do any good to "buff" the edges slightly with 3M wheel or dremel?


07-15-2012, 02:02 PM
Buffing might help would not hert. To get a beter fitting key go to a locksmith. you will pay alittle more for better quilty. The big box stores use a automatic machine that does an average jop for non skilled workers.

07-15-2012, 02:15 PM
Take your perfect key and measure each low spot on all the depressions of the good key with a vernier caliper and compare the dimensions with the depressions on the duplicate keys. Unless the operator of the key cutting machine is very careful setting up there will be discrepancies in the depth of each depression also the distance the center of the depression is from the depth stop on the key. You will find differences between the good key and the duplicates. Take the keys back with the discrepancies documented and ask to have new keys cut properly. It would take time but you could file your own duplicates if you buy blanks from the vendor. Just my 2c. Peter

07-15-2012, 03:40 PM
Buffing might help would not hert. To get a beter fitting key go to a locksmith. you will pay alittle more for better quilty. The big box stores use a automatic machine that does an average jop for non skilled workers.

+1 on this. You get what you pay for. All key cutting machines--and their operators--are not created equal...

Bob Fisher
07-15-2012, 04:01 PM
Too bad, I recently sold an old key cutter on CL for $50, WITH 550 assorted blanks. I never let the key cutter guy wire brush a key. I just run my pocket knife along the edges to remove the burs. If I need a key cut, I go to my little hole in the wall hardware store where they know how to cut a key. Bob.

07-15-2012, 05:50 PM
Most locksmiths keep their machines adjusted properly. Most big box stores rely on the company that sells the blanks for them to cut, to adjust their machines. This may or may not be done correctly. A lot of these machines may never have been adjusted since leaving the factory or at least since the first set up. The locksmith does charge more but they have the correct machine adjustment and blank for what you need. I'm sure cases may be different on both sides but majority cases seem to be as I have stated. An instructor of mine once told me, you may be able to turn on a machine but that doesn't make you qualified to operate it.

07-15-2012, 07:33 PM
Thanks guys. I'll try dragging my knife blade along the edge, if that doesn't help then I'll grab the mic and some files. Then, as a last resort I'll visit a locksmith and "explain" the problem.

Really need to replace the door as the outer skin is starting to delaminate. I've "rebuilt" the dead bolt several times over the years. I've held off replacing the door and lock for several years now due to all the locks being keyed alike. I guess I could have the locksmith key the new lock to the existing locks. Also years ago a friend "double keyed" the interior side of the dead bolt so that I could leave the key in it. If anyone ever took the key it would not open the outside lock, but the outside key would unlock the interior side of the dead bolt.


07-15-2012, 07:51 PM
As others suggested, compare your new keys to the old. Generally, if problems exist, its due to the key not sitting "flat" when cut - ie. one end's cuts will be consistently deeper than the other key's. If this is the case, take the key back. If the key seems to have been cut flat, then look at the depth. My experience with non-locksmith cut keys has been that typically the cuts are shallow due to predicting wear. A few seconds with a wire will has always cured it for me.

07-15-2012, 08:35 PM
I suspect that the problem is that you have a lock that is well made. :)

Check the good key. When you insert it, does it actually ride on one of the grooves milled down the side, or does the top of the key touch the top of the keyway? Most cheap locks use the top of the keyway as the surface that the key rubs against. Many quality locks use the grooves to ensure that the key is precisely located

Now compare that to the way a walmart key sits. Does it sit the same way? Many cheap keys use a milled slot that is a few thousandths wider so that it fits more locks. This allows the key to sit "higher" than the original.

Many key cutting machines register the key location against the back of the key and the shoulder ( or tip, depending on the key ). If the key is in fact riding on a groove, then it is that groove that needs to be used as the reference when aligning the original and duplicate.

Am old locksmith trick for "do not duplicate" keys is to make a good key that rides on the side grooves, then take around 4 or 5 thousandths off the back. That key will work perfectly, but every hardware store duplicate will not quite work.


07-15-2012, 08:38 PM
This is a very common problem and as others posted, getting a key cut by some kid who has no clue is not going to produce a duplicate. Those key cutting machines sit forever with no tune ups etc.

What i have done a couple of times is carefully clamp the two keys together, (good one against the bad one, and compare the teeth,, you'll be surprised how much difference there is.
Then if you can see good, carefully file the bad one to the same dimensions as the good one. This works.

A finicky project, but if enjoy challenges this is a good one to try.

07-15-2012, 08:39 PM
Yeah, I'd just take it to a real locksmith and not one of the big box places. Although I've had good luck at smaller, mom and pop hardware stores that have an older staff running the place. Running one of those generic key cutting machines well takes skill just like any machine tool, which really, is what they are.

When I was a teenage I work at a filling station/truck stop and we cut keys there. I was the guy that everybody came to to get keys cut. Even the guys that worked there longer than me would call me over whenever somebody asked to have a key made. They take proper setup just like any machine tool. Being a duplicating machine you have to set the template (original key) and the blank up correctly phased or the result will be what you've been getting.

07-15-2012, 08:44 PM
On a related note; anybody ever make a master Vidmar key? :D I have a master Vidmar key that literally fits every Vidmar cabinet in the world. They claim that they are impossible to duplicate but anything that can be made can be unmade. I've made a bunch but think I'm down to one spare.

07-15-2012, 08:49 PM
A locksmith will measure your key and
cut you a new key BY NUMBER.
That way any error will not duplicate.


07-16-2012, 10:26 AM
How old is the lock? With time the pins, the drivers and the cylinder plug become worn resulting in keys (however good a copy) that don't work without fiddling. Making copies of copies doesn't help either.

Get a copy made at a Locksmith. If that fails to solve the problem, get a new cylinder but keep one of the originals in a safe place to make copies from.

Screw WallyWorld. Support your local Locksmith, before that becomes another skilled trade that disappears in America.

07-16-2012, 10:50 AM
While I second the locksmith vs big box I took the easy way & installed one of the digital ones. Push a few buttons and...
Still accepts a key as backup

07-16-2012, 12:04 PM
Not sure if it was mentioned but if the lock is old enough it is not the key that is causing the trouble of "jiggling to open". The tumblers in the lock are worn and don't open to the exact spot they probably used to when new.

Try wire wheeling one of the new keys a bit and try it again, repeat.

07-16-2012, 02:47 PM
If the original key continues to work properly, the lock is not worn.

If you take it to a locksmith, They will probably use a better maintained version of an automatic duplicating machine. Measuring and cutting to code takes longer, and time is money in the locksmith business.

You can ask him to generate a new key from code instead of duplicating the old one. In the case of a Schlage (and many others) , the needed numbers are stamped on the original key.

While you can measure the key cuts and make a new one to specs, that makes the assumption that the lock has all standard pins. I have a set of pins that are in all lengths so I can change the bitting (pin combination) in a schlage, baldwin or kwikset lock to some very non standard settings. Trying to cut a key to "proper depths" will fail with a lock that has been re-keyed that way.


07-16-2012, 04:46 PM
Duplicate key nonni nonni, duplicate key nonni nonni,
I'll open her up with my duplicate key!

(Last refrain from a little ditty about Arthur arriving home after the campaign and finding he had lost the key to the lock on Guinevere's chastity belt. Sir Lancelot to the rescue ... ) :D

07-16-2012, 06:59 PM
Most of the trouble comes from key machines that are not adjusted properly.
Second most common is a copy is made of a copy of a copy etc. which compounds the tolance error.
One old trick if you suspect a worn key etc. is to put a piece of paper in the key holder before putting the key in it. Results in about 3 to 5/1000s difference in the cuts. Somethimes cures things.
John l

07-17-2012, 12:07 AM
The lock is going on 25 years old. I've had my "original" key for over 20 years. No jiggling the key to make it work, just any duplicates that have been made from it or my wifes duplicate. I think I'll dig out my calipers and files in the next few days and see where the problem is.


07-17-2012, 01:59 AM
I got tired of fishing and sorting my pockets for keys especially when my arms were full. Also would end up walking out to the shop only to have to walk 100' back to the shop to get the forgotten key. Lastly the kids when getting off the bus would forget or lose their keys requiring me to get off my arse and open the door for them. Thus I put in a few Schlage digital locks. I can assign temporary codes for house sitters and guests then later delete them. They work well.

07-17-2012, 11:30 AM
If the original key continues to work properly, the lock is not worn.


That is not true. It sounds like you have done some lock work. The outside barrel edges of the tumblers get worn down as the original key gets worn down and doesn't open the tumblers to their original point. Over time the whole deal gets looser and looser and actually worn in much like anything that moves allot. When a new key is cut with sharp points and pockets using an older key that is worn some everything is going to be off just a bit. This is why I mentioned the wire wheel earlier. One or two quick light wire wheelings of the new key round the high points off and round out the low points some essentially making it very much like the older worn in key. I have done it many times and it has worked nearly every time. Sometimes the lock was just to old and worn.

Now I am not a locksmith but like many here if something doesn't work I will play and tinker and take stuff apart to see whats going on. Not only to just have an understanding of them but like mentioned to change the tumbler combination on some locks. I have taken apart, fixed, and changed the configuration on many different styles of locks, ignitions, and the like.

I made all the locks on my camper to the same configuration as my master lock key so I didn't have to carry another key just for the seldom used camper.

A shot of lube every now and then is nice for locks too.

07-17-2012, 06:53 PM
That is not true. It sounds like you have done some lock work. The outside barrel edges of the tumblers get worn down as the original key gets worn down and doesn't open the tumblers to their original point. Over time the whole deal gets looser and looser and actually worn in much like anything that moves allot. When a new key is cut with sharp points and pockets using an older key that is worn some everything is going to be off just a bit. This is why I mentioned the wire wheel earlier.

Here is why I don't think that is correct.

The OP specified house keys, so the logical assumption is pin-tumbler locks. He did not specify location, so I'm guessing USA. He mentioned keys duplicated at mass market stores, so that limits it to normal pin tumbler cylinders, not the fancy ones like Medeco biaxial or Schlage Everest.

Given that, the lock works because a stack of pins protrude through the side of a core onto matching holes in the enclosing cylinder. When the place where the two pins meet is at the edge of the core, then the core is allowed to turn. When the stack is high or low the pin blocks the core from turning. A spring in the cylinder pushes the pins down to ensure that they are in position to block the lock. It is always the top pins that extend into the core when the key is removed.

The bottom pins are of varying lengths. When the wrong key is used, some combination of top and bottom pins block the shear line.

Virtually all locks are installed so that the key pushes the key up or to the side, and not down. This keeps spring fatigue from causing the lock to jam.

Let's look at wear. We will call the pin that the key touches the bottom pin, and the one it pushes against the top pin. The juncture where the cylinder meets the plug is the shear line. We will assume a 5 pin lock.

Most locks are made with unnecessarily fancy key shapes. The pins themselves only rest at 5 spots on the keys. Most of the time the pin is in the right place when it is at the bottom of one of the Vs. The peaks are there to make sure that the pins move to even the wear and to push the pin above the shear line so it can fall back into place. The pins are cone shaped on the ends to allow the pin to slide in and out as the key is inserted/retracted. On some keys the pin rests on the sides of the V, on others it rests on the bottom of the V. Most often it is the bottom.

If the key VALLEY wears, the pin will not push as high as it did before, and the top pin will catch as you try to turn it. The same if the pin wears. It becomes shorter and therefore will not push the top pin up enough to clear the sheer line. Keys do not work better (except for one case) as they age. They often get easier to insert.

If the key peaks wear, it does very little to the working of the lock.

The one case where they work better with age is when the key cut is just a little too short (less than .001) and the top pin catches on the edge of the core. Eventually it will carve a little ramp in the core. In that case the lock is getting broken in, not the key. It is making a very wide sheer line.

A common problem with department store key duplicators is that they use one cutting wheel for all profiles. This can result in the sides of the V being a little too steep or too shallow. If too narrow the pin will not touch the bottom of the V. Too shallow and a pin that is supposed to rest against the sides will touch the bottom instead.

A side note... A well made key does not move much in the core. It is supposed to register on the grooves of the key.

Best solution; take the key to a good locksmith who can provide OEM blanks and well cut keys.


07-17-2012, 07:31 PM
That is all true and I guess it all depends on what has worn the most in this case.

I was looking at it that the original key not only worn the bottom of the "bottom pins" lowering all the pins over time which cause the top pins to rub a little more every time the original key is used. Eventually this little bit of continual wear makes groves on the cylinder as well as the bore. When a copy of the old key is made not all the wear is cut into the new key. the new key has sharper points and gullies and can hold a or multiple pins (most of the time) higher then the worn key. Making either the bottom pins or the top pins to be out of their "groove" and catch something, being a burr, the cylinder, or the bore.

If he is going to have yet more keys made I would think it is worth the shot at least to try wire wheeling one of the copies and see what happens.

07-18-2012, 12:11 AM
Unfortunately, the fidelity of a copy depends on the machine used to create it. I have a machine with a cutting wheel that is fairly rounded. The tracer stylus is more pointed. It works as long as the details of the key are bigger than the radius on the edge of the cutting wheel. My experience has been that a dull wheel will result in more of a U and less of a flat bottom V.

Duplicating machines are simple tracers. If properly aligned and maintained they will recreate the original profile within limits of the cutter and tracer geometry. Like any machine the flex and play in the moving parts contribute to their inaccuracies.

By all means, a gentle wire wheel will remove burrs if there are any. A dull cutter will inevitably leave a wire edge.