Failure of Carbon Fiber Knives to Pass Metal Detector Screening

Over the past 18 years as a knifemaker, non-metallic knives have been a primary specialty of my shop. Like many other makers, Carbon Fiber has been the material of choice for the majority of those blades. Carbon Fiber (CF) has proven qualities of strength, toughness, and cutting ability that exceed other non-metallic composites.
Many other knifemakers have used CF in building tools for non-permissive-environments (NPE). My colleauge Ian Wendt, of Special Circumstances Inc, is a notable example. We have all believed that, being non-metallic, carbon fiber was capable of passing through a metal detector without causing it to alarm.
Working together, Ian and I have recently discovered that we were all wrong. Carbon fiber knives CAN be discovered by a metal detector.

In this video, “EM Field Eddy Current Induction In Carbon Fiber And The Implications For NPE Tools”, you can see Ian and I discuss our findings, and demonstrate the detection of carbon fiber knives by a metal detector.

Perhaps needless to say, I will no longer be producing carbon fiber knives.
Between myself and the other makers working in this field, a reasonable estimate is that there are thousands of carbon fiber knives in existence, and being relied upon. That practice is no longer recommended, as clear evidence shows they are not suitable for NPE use.

How Does This Happen?
In the simplest of terms, modern metal detectors use electrical current, passed through a coil, to generate a magnetic field. When that field passes over a metallic (or conductive) object, electric current is generated inside that object which creates it’s own magnetic field, that is then received by the receiver coil in the metal detector. This causes the detector to alarm.
Although carbon fiber is truly non-metallic, it is a conductive material. Being made up of multiple layers of hundreds of individual conductive carbon fibers, often interwoven, this means that a magnetic field will induce Eddy Currents within a piece of CF plate, such as a knife. That in turn creates a return magnetic field, received by the detector and alarmed on.

As demonstrated in the video, the angle at which the knife is positioned when passing through, or being passed over by, the metal detector does have an impact on it’s discovery, as does the size of the piece. This, along with poor technique for hand-wandings, likely accounts for the fact this flaw has gone unnoticed before. It seems obvious that many users of this type of tool have successfully passed them through metal-detector screenings. I have done it myself, and various customers of mine have as well.

This finding is not just important to me, my customers, and my work but to all those who have made or used a CF knife in one NPE setting or another. I encourage those of you reading this to share this information widely, in hopes that it will prevent any user, of any makers work, from being exposed to the risks inherent in discovery of their tools in an NPE.

What Am I Doing About It?
The failure of the selected material, CF, to perform a promised was not something I expected or had any knowledge of prior to this week. This has blindsided me, and undermined a large swath of my professional career for these past 18 years (the first custom knife I ever sold was a solid CF piece). We will make the best of it together, however. The end result of this is better, more reliable, tools.
I am immediately switching my production of non-metallic-knives from CF to G10, a high-pressure fiberglass laminate.. G10 is a material long used in knives, with excellent strength, that is fully non-metallic and non-conductive. Going forward everything will be made from G10 (or another suitable material, as my research continues).

For those of you who already own CF knives made by me, you have my apologies.

  • I will be contacting each of you, for whom I have contact information, about this directly. You’re encouraged if you don’t hear from me in the following days, to please reach out.
  • I cannot, and will not, be offering refunds. I will, however, not leave you hanging. I will be building a list of customers who need their knife or knives replaced with the same design in G10, and beginning to collect those knives from each of you. Collecting, patterning, and rebuilding each knife is a process that will take quite some time. Replacements for high-risk users will be prioritized, but even those will take time.
  • In that time you will see me make and sell other knives. I cannot afford to make only replacements for CF pieces, and stay in business. Your patience and understanding will be appreciated, and if you test those limits, I will cancel your replacement and return your original. I will offer frequent updates and maintain full transparency with the replacement process, expected wait times, and any delays. At this time, having not yet collected customer information for this process, I cannot make any statement as to the timeline, except to say “months”. That is subject to change.
  • If you do not want a replacement knife, know that I offer no guarantee of performance for any CF knife, and you use it at your own risk. I will offer you a discount on a future order with BFE Labs, if you choose to keep your CF knife.

Please note, I speak only for myself in this, and it is up to each individual maker to handle this discovery as best fits their business.

I will be continuing to collaborate with Special Circumstances Inc. on testing carbon fiber materials, and generating more detailed data on metal detector discovery of said material, for the furtherance of our craft and security research in general. If anyone reading this has relevant subject-matter-expertise, or access to testing equipment we haven’t been able to utilize yet (such as walk-through metal detectors), and you would like to help, please contact me.

Thank you for your support, and your patience. Please spread this information widely.

Morgan Atwood
Founder/Director BFE Labs

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