Lockpicking Forensics - RSS 2.0 Feed
Lockpicking Forensics - ATOM 1.0 Feed


Normal Wear

In order to identify compromise of a lock it is important to know what the lock components and keys look like when they are used normally.

The amount and nature of the wear on components varies and is highly dependent on the lock, key, and component materials. The most common material for pin-tumbler locking cylinders, keys, and components is brass. Cylinders and components (pins, levers, wafers, etc) also commonly use nickel-silver, steel, and other materials. Keys are made from a wide variety of materials besides brass, such as nickel-silver, aluminum, iron, steel, zamak, and various proprietary alloys.

The nature of wear also depends on the design of the key and the components. Unfortunately, I cannot display all possible combinations of designs and materials. Regardless, it is the duty of the forensic locksmith to conduct laboratory tests if an unknown combination is found during an investigation.

The following is a microscopic examination of different stages of wear on a standard pin-tumbler cylinder (Falcon FA3, 6 chambers, pinned for 5) that is made of brass. Bottom pins in this cylinder have rounded tips. Prior to disassembly, the key to this cylinder was used no more than ten times. For the sake of space, I will only show 1-2 pins of each stage, rather than all 5.


New pins are clean, with no dust, grease, or dirt. Light abrasions and corrosion may exist depending on how the pins were stored prior to being used in the lock. Factory original pins usually do not exhibit these characteristics. A clear indication that pin has not been used is the fresh milling marks around the tip of the pin.

A brand new pin-tumbler pin, with no scratches, dents, or other markings.

Up close, we notice many small imperfections in the tip of the pin. Very light scratches, dents, and bumps are visible. The dents and bumps are natural imperfections in the manufacturing process, while the light scratches are likely from the use of a key.

Close up of a brand new pin-tumbler pin, with distinctive milling marks.

The key for this lock is also new. It is factory original, made of brass, and has been cut with a high speed key machine. As stated above, it has been used a few times, and because of this we can see a light track in the center of the key where it has picked up lubricant from the pins.

A new (few uses) factory original key, cut on a high-speed key cutter.

The face of the plug is also clean on a new lock. There should be few scratches or dents and little dirt or corrosion. The keyway material is not damaged, and the material just inside the keyway should not have any markings.

The face of the plug in a new lock. No scratches, dents, dirt, or markings are visible.

250 Uses

A pin from a lock that has been used 250 times. Notice the light wear around the tip of the pin.

After 250 uses (roughly 3-6 months of use) a ring develops around the pin. This is the key gliding under the pins, spread around the tip because insertion and removal lightly rotates them back and forth. The key is also lightly polishing the pins, too.

Close up of previous image, wear at this magnification turns out to be removal of milling marks and light polishing.

Up close we can see that the ring is actually due to the milling marks starting to be removed and lightly polished. The pin has also been slightly distorted in the very center, also due to the key making contact with it.

At 250 uses, the key begins to show a small amount of wear and has picked up lubricant from use in the lock.

The key has also started to show signs of wear, mostly in the center where the pins have been touching it. In this particular case, wear resembles a staircase pattern. In addition, the key has picked up more lubricant, making the line on the key considerably darker.

The plug from a lock used 250 times shows signs of light wear from contact with top pins.

The plug is also showing signs of wear, caused by the top pins gently rubbing against it when the cylinder is turned. (Note: The top pins also show signs of wear because of this, but I have left them out to keep our examination simple.)

1,500 Uses

At 1,500 uses (roughly 1.5-2 years of use) a distinct change in the appears of the pins. The key has been used so many times that the milling marks have almost completely been removed. Again, slight scratches on the pin are being caused by the key becoming more jagged as it too wears down.

At 1,500 uses the pins in the lock are polished and almost completely lose their milling marks.

What is most interesting is that pin 5 (the furthest back) has considerably less wear, and more visible scratches. This all makes sense; it is only touched by the tip of the key, and the tip of the key is the most worn down because it makes contact with all of the pins.

At 1,500 uses the pin in the back of the lock (pin 5) show minimal wear compared to the previous photo.

The key continues to wear and collect lubricant. Image shown at high zoom to show the literal pits that are being created. At this point, certain ramps on the key may be acting like a file when going in and out of the lock. As seen above, this translates to more light scratches on the tips of the pins.

At 1,500 uses the key shows increased signs of wear, resembling a staircase pattern.

Of course, the plug and the top pins have continued to wear, with more brass being polished off and more pronounced staggering of the lubricant along the sides of the plug.

At 1,500 uses the plug continues to wear, with removing of material and depositing of lubricant both increasing.

5,000 Uses

At 5,000 uses the front pin has milling marks completely removed and is polished to a uniform surface.

At 5,000 uses (roughly 5-6 years of use) the front pin has no milling marks, and almost all scratches have been polished away. From this point on wear looks similar to this, with light markings sometimes being created by wear of the key.

At 5,000 uses the back pin continues to wear but still shows milling marks and reduced wear compared to the front pin.

Compared to other pins, pin 5 (the farthest back) continues to show reduced signs of wear and retain its milling marks. We can also now see that wear is not evenly distributed on this pin, as it resembles an oval shape. Compare with above picture and 1,500 use pictures.

Close-up picture of the key after 5,000 uses. Large craters of material have been removed and lubricant deposited.

They key continues to wear down, with small craters from the previous example now very large and uneven. Slight imperfections like this in the key will cause light, seemingly random scratching on the soft brass on the pins. Stronger key materials may even act as a file against pins.

The plug shows increased signs of wear after 5,000 uses.

At 5,000 uses the plug continues to show increased wear, though not much has changed. More pronounced staggering of wear and lubricant can be seen along the circumfrence of the plug. Compare with example at 1,500 uses.

Over time the tip of the key will cause markings on the face of the lock due to user error.

The face of a lock that has seen moderate to heavy use will have many dents and imperfections caused by normal use. How many times have you went to unlock a door and slightly missed the keyway? In the photo, many small dents and scratches from normal use are visible.

Over time the shoulder of the key causes markings above the keyway of the lock. This is not the same as marks left by key bumping.

In shoulder stopped locks (almost all modern locks qualify), continued use will cause light impact marks along the face of the plug. This is normal, and should not be confused with the extreme material displacement that occurs during key bumping.

Other Factors

In cylinder based locks, the use of different materials for the plug and cylinder reduces wear. This also applies to wear on the pins, but most changes to pin material are to increase resistance to destructive entry, not longevity.

The speed at which a key was cut will translate into smooth or jagged ramps on the key. In some cases, a sufficiently strong key material, such as steel, with jagged ramps acts as a file on the pins, causing wear at an accelerated rate. See the key analysis page for more information.