Benchmade Infidel 3.91in Automatic Folding Knives Review

Meet the **Benchmade Infidel 3.91in Automatic Folding Knives**: First Thoughts

For years, I’ve sought a reliable, fast-deploying cutting tool that could handle a variety of tasks without fuss, a constant companion for both my workshop and less predictable field excursions. The Benchmade Infidel 3.91in Automatic Folding Knives seemed to promise just that, bridging the gap between tactical readiness and practical utility. My previous experiences with automatic knives have been mixed; some were flimsy, others unreliable, but the Benchmade name carries a certain gravitas. This particular model, with its out-the-front (OTF) action and double-edged blade, presented an intriguing blend of form and function. I had considered other OTF knives, and even some high-end assisted openers, but the Infidel’s reputation for robust construction and rapid deployment made it the frontrunner. Initial impressions upon unboxing were strong: a solid, weighty feel in the hand, indicative of quality materials. It instilled a sense of quiet confidence, a feeling that this tool was built for purpose.

Real-World Testing: Putting **Benchmade Infidel 3.91in Automatic Folding Knives** to the Test

First Use Experience

My first real test of this automatic knife was during a particularly busy Saturday in the workshop. I needed to quickly open several boxes of incoming parts, then immediately transition to trimming some excess material from a prototype I was assembling. The Infidel’s out-the-front deployment was astonishingly fast; the thumb slide engaged with a satisfying thwack, presenting the blade in an instant. This speed was invaluable when I needed to switch between tasks rapidly, eliminating the fumbling associated with more conventional folding knives. I also used it to strip some wire insulation and to make precise cuts on a piece of dense polymer, tasks where a sharp, stable blade is paramount.

The double-edged nature of the blade proved surprisingly useful in the workshop. I could make a cut in either direction without needing to reorient my grip or the workpiece. For instance, when trimming flashing from a molded part, I could execute a clean slice in both forward and reverse motions with equal ease. The handle’s anodized aluminum felt secure even with slightly greasy hands, contributing to confident control. A minor surprise was the slight blade play I noticed when the blade was fully extended, a detail I’ll explore further, but it didn’t impede my immediate tasks.

Extended Use & Reliability

Weeks turned into months, and the Benchmade Infidel 3.91in Automatic Folding Knives became a go-to tool. It accompanied me on several site visits, where it was used for everything from opening sealed packages of documentation to making minor adjustments on equipment in the field. I’ve even used it for impromptu food prep during quick field lunches, where its sharpness and double-edge made slicing through a sandwich or an apple remarkably efficient. The knife has seen its fair share of dust and grit from the workshop floor, and even a light spray of coolant, yet it has continued to perform flawlessly.

Despite regular use, the blade’s sharpness has held up exceptionally well. The D2 tool steel has proven to be quite resilient, requiring only a few light touch-ups on a ceramic rod to maintain its edge. The OTF mechanism remains robust, with the same crisp deployment I experienced on day one. The integrated cleaning port is a thoughtful addition; a quick puff of compressed air usually clears any debris that might accumulate. Compared to some less expensive automatic knives I’ve owned, which developed stiffness or failed to retract reliably, this Benchmade model exhibits a level of durability and consistent performance that justifies its premium positioning.

Breaking Down the Features of **Benchmade Infidel 3.91in Automatic Folding Knives**

Specifications

The Benchmade Infidel 3.91in Automatic Folding Knives boasts a blade length of 3.91 inches, providing a substantial cutting surface without becoming unwieldy. Its double-edged dagger shape, forged from D2 tool steel, offers versatility for piercing and slicing. The black anodized machined 6061-T6 aluminum handle measures 0.59 inches thick, providing a comfortable and secure grip with an overall length of 8.95 inches when deployed. When closed, it measures 4.8 inches, making it surprisingly compact for an OTF knife. The blade thickness is 0.118 inches, which balances strength with a keen edge.

The handle material, 6061-T6 aluminum, is known for its excellent strength-to-weight ratio and corrosion resistance, contributing to the knife’s 5 oz weight, making it substantial but not burdensome. The D2 tool steel blade has a hardness rating of 60-62 HRC, a desirable range for edge retention and toughness, though it can be prone to corrosion if not maintained. The plain, non-serrated blade is ideal for precise cutting tasks. The ambidextrous thumb slide for deployment and retraction is a key functional feature, allowing for quick and easy operation by either hand. This knife is classified as a pocket knife and tactical tool, reflecting its robust construction and rapid deployment capabilities. The included Cordura sheath is MOLLE compatible, adding to its utility for carry.

Performance & Functionality

The primary function of the Benchmade Infidel 3.91in Automatic Folding Knives is rapid, reliable blade deployment and cutting. In this regard, it excels. The OTF mechanism fires the 3.91-inch D2 blade with impressive speed and authority, feeling solid and precise. The double-edged dagger profile is exceptionally effective for piercing, and when used for slicing, it offers a wide cutting surface. I found its performance in the workshop to be outstanding, slicing through packing tape, cardboard, and even denser materials like foam board with minimal effort.

However, the minor blade play when fully extended is a noticeable, albeit not catastrophic, imperfection. While it doesn’t compromise the knife’s ability to cut, it does detract from the otherwise flawless feel of the tool. For tasks requiring absolute rigidity, like prying or extremely delicate precision work, this play might be a concern for some users. Compared to single-action OTF knives, the double-action of the Infidel is generally smoother and more robust, though the slight play is something Benchmade could potentially refine in future iterations.

Design & Ergonomics

The design of the Benchmade Infidel 3.91in Automatic Folding Knives is a masterclass in tactical aesthetics and practical ergonomics. The black anodized machined 6061-T6 aluminum handle is sculpted for a secure grip, with subtle contours that fit naturally into the hand. Its 0.59-inch thickness provides ample purchase, and the textured surface ensures it won’t easily slip, even under duress. The overall feel is one of solid, robust construction; there are no rattles or loose parts beyond the aforementioned minor blade play.

The thumb slide is positioned intelligently for easy access with the index finger, allowing for swift deployment and retraction. The deep-carry pocket clip is sturdy and allows the knife to sit discreetly in the pocket, minimizing its profile. The inclusion of an integrated cleaning port is a thoughtful design element, simplifying maintenance and ensuring the longevity of the complex internal mechanism. The balanced weight distribution contributes to a comfortable feel during extended use.

Durability & Maintenance

The Benchmade Infidel 3.91in Automatic Folding Knives is built to last. The 6061-T6 aluminum handle is highly resistant to impacts and corrosion, and the D2 tool steel blade, while requiring occasional oiling to prevent surface rust, offers excellent wear resistance. I’ve subjected this knife to demanding conditions, including exposure to dust, moderate moisture, and the general wear and tear of workshop use, and it has shown no significant signs of degradation.

Maintenance is straightforward. The integrated cleaning port allows for quick clearing of debris. Regular cleaning with a soft cloth and a light application of lubricant on the blade and mechanism are generally sufficient. The 10-year limited warranty offered by Benchmade also provides peace of mind regarding its long-term durability. The robust construction suggests it will withstand typical use for many years, making it a reliable investment rather than a disposable tool.

Accessories and Customization Options

The Benchmade Infidel 3.91in Automatic Folding Knives comes with a MOLLE compatible soft Cordura sheath, which is functional for belt or pack attachment. While this sheath is adequate for basic carry, it doesn’t offer the same level of protection or quick access as some aftermarket Kydex or leather options. Benchmade knives are generally well-supported with accessories, but customization options for OTF knives are more limited compared to fixed blades or traditional folders.

For this particular model, upgrades typically focus on enhancing the carry experience rather than modifying the knife itself. While aftermarket clips can be found, the original deep-carry pocket clip is well-designed and effective. The focus of this knife is its inherent functionality, and while the included sheath is practical, investing in a custom sheath might be beneficial for those who prioritize rapid access or enhanced protection.

Pros and Cons of **Benchmade Infidel 3.91in Automatic Folding Knives**

Who Should Buy **Benchmade Infidel 3.91in Automatic Folding Knives**?

The Benchmade Infidel 3.91in Automatic Folding Knives is ideally suited for individuals who require rapid, dependable blade deployment in demanding environments. This includes workshop professionals who frequently open packages or perform quick cutting tasks, tactical professionals who need a fast-access tool, and outdoor enthusiasts who appreciate robust, high-performance gear. Its double-edged design also appeals to those who value versatility in their cutting tools.

Anyone seeking an ultra-lightweight or budget-friendly option should likely look elsewhere. This knife is for those who prioritize proven quality, speed, and durability, and are willing to invest in a premium tool. For those who find the slight blade play a potential issue, or who require absolute rock-solid rigidity for heavy-duty prying, exploring other high-end OTF options or even a high-quality fixed blade might be more appropriate. A good quality lubricant and a soft cloth for maintenance are highly recommended accessories to keep the blade and mechanism in top condition.

Conclusion on **Benchmade Infidel 3.91in Automatic Folding Knives**

The Benchmade Infidel 3.91in Automatic Folding Knives stands as a testament to exceptional engineering and premium craftsmanship. Its rapid out-the-front deployment, coupled with a durable D2 steel blade and a rugged aluminum handle, makes it a highly capable tool for a wide range of applications. While the minor blade play upon extension is a point of critique, it does little to diminish the overall impressive performance and reliability this knife offers. For those who demand speed, precision, and enduring quality in their cutting tools, and who understand the value of investing in a top-tier product, this Benchmade model is an excellent, albeit costly, choice. I would readily recommend it to professionals and enthusiasts who can leverage its unique capabilities and appreciate the peace of mind that comes with owning a tool built to last.