Using the New Kobra Readers

Sept. 1, 2007
I've been an automotive locksmith for almost 35 years now, and I've used just about every technique and tool there is to make keys to vehicles at one time or another...

I've been an automotive locksmith for almost 35 years now, and I've used just about every technique and tool there is to make keys to vehicles at one time or another. Since I grew up making keys by impression, that is still my fall-back method when all else fails, but my 55-year-old eyes make that a little harder than it used to be. And then there is also the fact that I seem to be getting lazier as I age, or at least more frugal with my energy. Now, when I set out to generate a key for a car, I'm looking for the fastest and easiest method.

For a while there, it was almost too easy – just pick up a phone and get a code number from the VIN –but those days are fading fast. Today, when I have to make keys for a vehicle, the first tool I reach for is one of the new Kobra Readers shown in Photo 1. With the Kobra Reader, I can usually decode the door lock and / or the trunk lock in a matter of minutes, do a simple two or three cut progression in the ignition and I'm done. It sure beats the heck out of pulling door panels and ignition locks!

Most modern vehicles use a lock system that incorporates wafer-tumbler door locks and a sidebar or wafer tumbler ignition. In most cases the cuts that are found in the door lock will give you 60 to 80 percent of the information that you need to make the final key. If the car is equipped with a trunk lock, you can often get the rest of the information you need to make the key without even touching the ignition lock.

At this time there are Kobra Readers available for six different lock systems:

• Chrysler 8-cut / 7-cut systems

• Ford 8-cut systems using cuts 1 – 6 in the door

• Ford 8-cut systems using cuts 2 – 7 in the door

• Ford 10-cut system

• GM 10-cut system 75 groove key

• Mitsubishi 8-cut systems using the MIT 6 keyway

With these six readers, my work at the local auto auctions is a lot easier. When I need to decode one of these vehicles, I can generally have a working mechanical key made in just a few minutes, and then turn my attention to programming any transponders if needed.

In order to understand how the Kobra Readers work, it's necessary to understand the construction of wafer-tumbler locks. Photo 2 shows a typical wafer tumbler. The three letters each refer to a different part of the wafer. Each part plays a role in the operation of the Kobra Reader. Let's take a look at what these parts are and how they allow the Kobra Reader to decode the lock.

The section marked “A” in Photo 2 is the uppermost portion of the tumbler, and this part contacts the inner surface of the lock housing when the tumbler is in the “rest” position. The rest position is the normal position of the tumbler when there is no key in the lock. The pressure of the spring pushes the tumbler up until part “A” contacts the inside of the lock housing, at which point the tumbler can go no further. (The terms “up” and “down” as I am using them here are relative only to the photo and in reality the lock could be mounted in any position.)

The section of Photo 2 marked as “B” is the spring tab. The spring maintains tension between this tab and the base of the chamber that contains the spring. In the rest position the spring is as fully extended as possible inside the lock.

Section “C” is the lower portion of the tumbler. The width of this portion determines the depth of the cut on the key. The wider this portion is, the deeper the cut will be. It is this portion of the tumbler that the Kobra Reader measures in order to decode the lock.

Now, let's take a look at the Kobra Reader in detail. Photo 3 shows a GM 10-cut Kobra Reader. The slide is held captive in the unit so that it cannot get lost or damaged. Near the tip of the blade is the trap notch, which traps each tumbler in the lock, one at a time so that it can be decoded with the slide. When the tool is being used, the dimples on the side of the blade are used as a guide to determine which tumbler is trapped so that you always know exactly which tumbler is being decoded. The even numbered cuts are shown on one side of the blade and the odd numbered cuts are shown on the other. As shown in Photo 4, each Kobra reader features a high-intensity LED illuminator that surrounds a high-contrast scale to make decoding at night much easier.

When the Kobra reader is in use, as shown in Photo 5, a single tumbler is trapped inside the trap notch and then the slide is pushed in until the angled tip of the slide makes contact with the tumbler. When the slide contacts the tumbler, the index mark on the slide will align with the scale as shown in Photo 6, giving you the precise depth of the tumbler that is being read. Note also how the dimple on the side of the blade aligns with the face cap to show you which tumbler is being decoded. (Because of different designs of some face caps the dimple will not always align as perfectly as in the photo, but it will always be close.) The design of the Kobra Reader holds and supports the slide in the proper alignment regardless of its position, so it yields an extremely accurate measurement of the tumbler depth that would not be possible if the slide were free to “float.”

In Photo 6, the position of the slide indicates that the tumbler being decoded is a number three depth. The deeper the cut on the key, the deeper part “C” of the tumbler will extend into the keyway. A shallow cut will allow the angled tip of the slide to go further into the lock than a deep cut. The mark on the scale closest to the lock will be the shallowest cut in the system, while the mark farthest away from the lock will be the deepest cut. With a little practice, you can trap each tumbler in the lock and decode it in just a few minutes. And the lighted scale makes working with the Kobra Reader at night a real pleasure.


The process of using the Kobra Reader is easy and it will quickly become routine as you use the tool on a regular basis. All you have to do is follow the steps outlined below in order to decode most locks:

1. Push the slide as far in as it will go to cover the trap notch, then insert the tool into the lock as far as it will go.

2. Pull the slide back in order to expose the trap notch and then pull out on the tool until the tumbler drops into the trap notch.

3. Using the dimples on the side of the tool, determine which tumbler you have trapped.

4. Rock the tool slightly from side to side to make sure that the tumbler has dropped as far in to the trap notch as possible.

5. Push in on the tool to bind the tumbler, then while maintaining pressure on the tumbler, push in gently on the slide until it stops.

6. Take your reading from the scale on the tool and write it down!

7. Release the pressure on the tumbler and then push the slide in as far as it will go to lift the tumbler and release the tool.

8. Pull the tool out until the index on the side of the tool shows that you are in position to trap the next tumbler. Repeat the above procedure to read each tumbler in turn and then flip the tool over to read the tumblers on the opposite side of the lock.

When using the Kobra Reader, there are a few techniques that you need to understand in order to get the most from your tool:

Always begin by cleaning the lock with a good solvent or lubricant. The Kobra Reader is precisely machined to give you the most accurate reading possible, and dirt or crud in the lock will only make the job harder.

Make sure that the tumbler has dropped all the way to the rest position by rocking the tool slightly after the tumbler is trapped to fully seat the tumbler in the slot.

Push in on the tool to bind the tumbler as you take the reading so that the slide stops against the tumbler instead of lifting it.

When in doubt, make the cuts on your key high – you can always cut them deeper, but it's impossible to go the other way.

On older vehicles expect the tumblers near the face of the lock to be more worn, and give a deeper reading than the ones at the tip of the keyway.

On particularly worn locks, pulling out on the reader, rather than pushing in on the reader, may help you to get better readings.

The Kobra Reader is designed to work on door and trunk locks only. Do not attempt to use the tool on the ignition lock.

Once you have decoded the locks, you can cut your key and try it in the locks. When you have a good working key, you can generally use a simple progression to finish your key in the ignition. In the case of the Ford 10-cut system, I generally use try-out keys in the ignition after I have decoded the door lock.

Just as with any other tool, having a good understanding of the lock system that you are working on will make your job much easier. Even though I've been at this job longer than most in the business, I still look up most vehicles in a reference manual before I start just to make sure that I know which tumblers to expect in each lock.

For more information, contact Lockmasters Inc., telephone 800-654-0637, online at